Over centuries, this curiosity evolved into a scientific pursuit, blending astronomy, biology, chemistry, and philosophy into a single, thrilling endeavor: to find life elsewhere in the cosmos.

From Galileo's telescope to the James Webb Space Telescope, each technological leap has brought us closer to answering that age-old question. We've sent probes to Mars, listened for alien signals through SETI, and discovered thousands of exoplanets orbiting distant stars. Along the way, we've refined our understanding of what life is, how it might arise, and where it could thrive — even in the most extreme environments.

This quiz explores the milestones, theories, and missions that have defined the search for extraterrestrial life.

Whether you're a space science enthusiast or just curious about the universe's biggest mystery, this challenge will stretch your mind across time and space.

Try it out below and see how well you score!

From ancient myths about gods descending from the heavens to 20th-century UFO sightings and today's hunt for exoplanets, the question of whether we are alone in the universe has never stopped captivating us. From microbial fossils on Mars to interstellar comets to mysterious signals in deep space, there is a timeless curiosity around extraterrestrials.

Journalist Becky Ferreira dives into this rich history in her new book "First Contact: The Story of Our Obsession with Aliens" (Workman Publishing, 2025). In a conversation with Space.com, Ferreira discusses the myths that shape our understanding of aliens (her newsletter dives into this further) and why real contact might look nothing like what Hollywood has taught us to expect.

Space.com: There are a lot of books about aliens out there. What made you want to add your perspectives to this tradition? 

Becky Ferreira: My editor for this book approached me with the idea, and when I saw it, I thought, "Oh aren't there so many alien books already?" But I should have known as a reporter that it's an inexhaustible subject.

For me, it also felt like the right time. There’s so much happening in the scientific search for alien life, but also more openness toward the UFO community and a posture of transparency from the government. I wanted the book to touch all those sides — the science, the pop culture, the history — and to do it in a short, visual, and kind of snarky way that invites people in.

Space.com: What is an alien trope you are tired of?

Ferreira: I love this question! Definitely the Messianic alien. And I’m sorry to the Superman fans! I like the new "Superman" movie, but I’m tired of stories where a superpowered being comes down to save humanity from itself. It’s not just aliens — it’s part of this larger myth we have that someone else will fix everything for us.

That idea goes way back — it’s basically a modern version of waiting for the gods, or the rapture. But I think it’s dangerous because it teaches us to wait for salvation instead of taking action ourselves.

I’d love to see more Robin Hood-type stories, where regular people, not superheroes, actually organize and make change for themselves. We need narratives that empower us, not ones that make us dependent on alien saviors.

Space.com: On the flip side, what kind of alien tropes would you like to see more of?

Ferreira: I love the truly strange aliens — stories like "Solaris" or "Arrival," where you have to completely rethink how you perceive the universe. Those stories feel more realistic to me, because if we do encounter intelligent life, it probably won’t think like us at all.

I’m fascinated by the idea of aliens who have a worldview that’s totally different, maybe even impossible for us to fully understand. Like the heptapods in "Arrival," who experience time all at once — that’s such a wild concept.

And honestly, I’d love to see more stories about microbes. What if we found a fossilized microbe on Mars that’s four billion years old? It’s tiny, it’s dead, it’s not a civilization — but it would completely change how we see life in the universe. Pop culture hasn’t really processed how monumental that kind of discovery would be.

Space.com: What is something you wanted to include in the book but couldn't due to narrative constraints or word limits? 

Ferreira: I finished the manuscript in January 2025, and of course all these fascinating discoveries happened right after — new exoplanet biosignatures, possible biosignatures on Mars.

There’s also a section on the rights of aliens that I wish I could have expanded. Like, what are the legal rights of a microbe on Mars? That sounds silly, but it’s actually a really important question. We’re doing all these astrobiological projects, and at some point we’ll have to decide how to treat what we find. You could write a whole book just about that.

Space.com: One of the hottest topics right now is Comet 3I/ATLAS, the newfound interstellar comet. You wrote about 'Oumuamua in your book — what do you make of this new one?

Ferreira: I think it’s the coolest thing ever! I couldn’t include it because of timing, but I’ve been obsessed. I love that we’re in an age where we can detect these interstellar objects at all. And with the Vera Rubin Observatory active I think by the end of the decade, we’ll have a whole census of them.

What’s exciting about 3I/ATLAS is that it’s like a time capsule — a piece of another star system passing through ours. Some scientists have even suggested it could be older than the solar system, which is wild. These are literal visitors from other worlds, and they help us see beyond our neighborhood. It’s like the universe is delivering us souvenirs from deep time.

Space.com:  If you could tell the public one thing about aliens — to clear up misconceptions or reframe the conversation — what would it be?

Ferreira: That our conception of aliens is human. I know that sounds obvious, but it’s so important. Aliens mean different things to different people, but the fascination itself is universal. Every culture has some story about beings from the sky — it’s part of who we are.

For people skeptical of UFOs, I get that — I used to be, too. But when I was researching this book, I realized a lot of those accounts are very persuasive. That doesn’t mean they’re extraterrestrial, but something happened. And I think it’s great that we’re finally talking about it without stigma.

For people skeptical of NASA or the government, I’d say: those institutions have extremely high standards for what counts as evidence. I don’t think they’re being secretive — they’re just careful. We’re all profoundly obsessed with aliens, but we need to give each other a little grace for what that means.

Because if we do ever find life out there, it’s going to change everything — spiritually, culturally, scientifically. And we’ll need everyone, skeptics and believers alike, to help us understand what that means for our place in the cosmos.

The TV series Alien:Earth has introduced a number of new creatures to the much loved, albeit terrifying, Alien franchise.

But how realistic are the new aliens? That's a question that we – a trio of scientists who are also great fans of the franchise and show – have tried to tackle with a ranking. To be clear, we are not trying to find flaws in the show. Like many fans we are simply having fun using science to analyze the creatures.

All species in the series draw inspiration from real living organisms and processes seen on Earth, but crank it up to the extreme. We therefore won't explore all those parallels, but instead focus on how plausible the organisms are in terms of underlying processes such as physics, chemistry, metabolism and evolution.

1. The tick

Our most plausible creature is the large blood-sucking tick. On Earth, the deer tick Ixodes do swell to the size of a walnut when feeding, which is not too different from the Alien:Earth tick. In the show, we see it attack the jugular and quickly take on a couple of pints of blood.

The perhaps surprisingly quick death of the unfortunate prey most likely results from hemorrhagic shock due to how quickly the blood is lost. It is possible that some sort of chemical agent (perhaps an anticoagulant, as has repeatedly evolved in blood predators on Earth) is also injected. We do see a defence mechanism in episode five where the ticks release an airborne toxin to prevent them being removed from their host. Chemical defenses like poisons and venom are common in animals and plants on Earth to deter predators.

In later episodes, we see it break containment (with the help of another alien) but we’ll assume it is simply seeking a body of water to lay its tadpoles in, rather than exhibiting intelligence. Horrifically, we see nothing that completely prohibits a life form like this.

2. D. plumbicare (the plant pod)

This creature, which as discovered and named in the show by the crew of the USCSS Maginot, benefits from not having been seen much (at the stage of writing, we have viewed the first six episodes). As the series progresses, it could move down our list. Initially, the character Kirsh questions whether it is flora or fauna. The science officer's analysis ultimately shows they classify it as a carnivorous plant. Its green color could indicate it also uses chlorophyll the way photosynthetic organisms like plants do on Earth.

However, a near spherical body is in fact the worst structure for photosynthesis. It lacks any of the surface area enhancing adaptations you’d expect from a photosynthetic organism, such as leaves. This would be particularly important given it appears to hang underneath covering structures like cave roofs. Perhaps this is why it needs to capture prey: rather than evolving more efficient light capturing mechanisms, it instead alternates between photosynthesis and predation, depending on the resources available.

This is known as mixotrophy in science, but is a feature only of single-cell organisms on Earth. "Carnivorous" plants are not mixotrophs as they merely source compounds like nitrates, potassium and phosphorus from captured insects, rather than carbohydrates. Animals are heterotrophic, meaning they get energy by consuming other organisms.

Some organisms, such as corals, have bacterial symbiotes – "friendly" parasites – that can photosynthesize energy for them from the sun, which could be the case here.

3. Trypanohyncha ocellus

T. ocellus is the lovable little eyeball octopus parasite. It attacks its host, removing an eyeball and then takes over entirely via connections to the brain.

This may seem like pure science fiction, but there are parasites on Earth that replace body parts and even control their host's behavior. However, the latter are usually relatively simple organisms, like the Ophiocordyceps fungus where taking over the brain of another animal is a necessary part of their life cycle. The behavioral changes these parasites induce are simple, such as moving the host towards light, water or the scent of a predator.

Toxoplasma gondii, for example, is a parasite that alters the behavior of mice, making them less avoidant of the smell of cat urine. The infected mice are therefore more likely to be eaten by cats, which then spread long-lasting parasite spores in their feces.

T. ocellus, in contrast, is very mobile, highly intelligent and strong, showing behavior like monitoring situations and distracting humans. This behavior is plausible with distributed ganglia (clusters of nerve cells) in the tentacles, similar to octopuses.

The length of these tentacles, however, exceeds that of similar structures on Earth, such as chameleon tongues, and is therefore somewhat implausible (but nevertheless incredibly cool). Our main issue here is why it needs to be parasitic at all – this is ultimately a formidable life form without requiring that.

4. The fly

First seen in episode 6, the fly appears to consume metal and metal ores and it pre-digests its food by spitting an enzyme, similar to flies on earth. Our main issue with it is that it's unclear whether this is a supplement (such as iron and other trace elements in our diet) or a main energy source.

There is a process on Earth known as chemolithotrophy (literally "rock eating") in which energy and biomass production can be harnessed by oxidation (removal of electrons from) of geochemicals – including iron, manganese and other metals.

On Earth, this is exclusive to single celled archaea such as Ferroplasma and bacteria such as Acidithiobacillus, organisms generally associated with very slow growth. Multicellularity is energetically demanding, not to mention flying, meaning metal oxidation is not a very plausible energy source for the fly.

Of course, the metal could simply be a supplement, albeit a very large one, needed to create a metallic shell. Biomineralization of iron compounds into the teeth of marine molluscs like chitons and limpets, who need hard teeth graze on rocky surfaces, is well documented. A similar mechanism could explain the hard metals in the Xenomorph's exoskeleton (which it needs to be able to scratch through the metal in a ship's hull).

5. The Xenomorph

The Xenomorph might come in at the bottom of this plausibility ranking, but it takes the top spot in our hearts/chests. The main problem with it is its impossibly fast growth rate, transitioning from a relatively small chest-burster to a fully grown adult in a very short period of time.

Very crudely, if we assume it has a similar metabolic efficiency to humans, and that it weighs roughly 100 kg, then it would need to consume and convert millions of calories of food (over a ton of pork-like meat) in what seems to be a few days at most. Of course, it could have a much higher metabolic efficiency than humans, though it would always be bound by the conservation of mass and energy. You can't acquire more biomass than you consume. And we never see it eat, not even its initial host.

Circumventing this would require an ultra dense (entirely hypothetical) energy source that it carries with it from the egg (Ovomorph). But energy has to enter the system at some point, implying the Queen would have to eat or capture huge amounts of energy somehow.

Another issue for the Xenomorph is that, if it did need to eat the huge amount of creatures it kills, it would rapidly deplete any prey resource and there would probably be no stable ecosystem that could support it. However, in the expanded universe, it seems that the Xenomorphs are artificial beings, created from a bio-weapon intended to obliterate an ecosystem, leaving a clean slate. In which case, they seem very effective.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Planets lacking plate tectonics and sufficient carbon dioxide and oxygen could make advanced civilizations like ours extremely rare, Manuel Scherf and Helmut Lammer of the Austrian Academy of Sciences suggested during a presentation at the Europlanet Science Congress and the Division for Planetary Science (EPSC-DPS) in Helsinki earlier this month.

According to their research, for a biosphere to persist long enough to allow for the evolution of complex life and subsequent advanced technology, an Earth-like planet needs to meet certain criteria.

First, there must be enough carbon dioxide to sustain photosynthesis and prevent atmospheric escape — but not too much that the atmosphere becomes toxic or traps too much heat. The key to this balance is plate tectonics, which regulate the amount of atmospheric carbon dioxide via the carbon-silicate cycle.

But plate tectonics won't maintain the biosphere forever. "At some point, enough carbon dioxide will be drawn from the atmosphere so that photosynthesis will stop working. For the Earth, that's expected to happen in about 200 million to roughly one billion years," Scherf said in a statement. Thus, a planet would also need a life-sustaining biosphere that lasts longer than the time it takes for technologically intelligent life to evolve. On Earth, that evolution took 4.5 billion years.

Second, a world must have a nitrogen-oxygen dominant atmosphere to develop an advanced civilization. Oxygen, in particular, is crucial not only for biology but also for technological advancement. For example, levels below about 18% oxygen could prevent the use of fire, which historically has been essential for metalworking and thus the development of advanced tools.

The team created models to compare the lifespans of biospheres with various atmospheric compositions to the amount of time it might take advanced civilizations to evolve. They concluded that if an advanced technological civilization were to exist in our Milky Way galaxy, the closest it would be to Earth is likely about 33,000 light-years away. Such a civilization would also have to survive for at least 280,000 years — and possibly much longer — for there to be any chance it overlaps with ours in time.

In other words, the odds are very slim that we coexist with another intelligent civilization in the Milky Way.

Despite the grim outlook, the authors encourage continued efforts, especially through SETI (the search for extraterrestrial intelligence). "Although ETIs [extraterrestrial intelligences] might be rare, there is only one way to really find out, and that is by searching for it," said Scherf. "If these searches find nothing, it makes our theory more likely, and if SETI does find something, then it will be one of the biggest scientific breakthroughs ever achieved, as we would know that we are not alone in the universe."

Yet it sometimes feels as if sci-fi and fantasy "canon" in sci-fi and fantasy is the most sacred of sacred cows. Movies and TV shows frequently tie themselves in knots trying to avoid contradicting throwaway lines of dialogue uttered decades earlier. Fans — and I'll admit I've been as guilty of this as anyone — have always been happy to flag up inconsistencies in franchise lore, while the Marvel Cinematic Universe has built its entire brand on labyrinthine continuity. Lucasfilm even employs its own "Keeper of the Holocron" to stay on top of the vast timeline of a galaxy far, far away.

But while consistency is undoubtedly important, it shouldn't come at the expense of good stories. "Alien: Earth" showrunner Noah Hawley and the rest of the creative team seem to have realized this, as the show has adopted a much looser approach to canon than most of its genre counterparts.

The show is set just two years before the USCSS Nostromo crew touched down on LV-426, and brought something very nasty on board. However, "Alien: Earth" never worries about the fact that the catastrophic crash of the USCSS Maginot — as well as Prodigy and the three other non-Weyland-Yutani corporations ruling the world — have never been mentioned before. Nor does it get hung up on its unlikely chronology, or get sidetracked by the events of the Prometheus and Covenant missions that departed a few decades prior. The multipurpose black goo that displayed magical properties in Ridley Scott's prequel movies is, so far, conspicuous by its absence

Instead we've been introduced to a whole new ecosystem featuring acid-spewing bugs, and a freaky, parasitic eye on legs that may just be orchestrating the whole show. After being retconned as the result of a malevolent android's morally dubious experiments in "Covenant", the Xenomorph is — for now, at least — back to being a more evolution-adjacent apex predator.

Crucially, Alien: Earth has kept the key pillars that helped make "Alien" and "Aliens" all-time classics — the eggs, the Facehuggers, the acid for blood— and treated everything else as malleable. Other sci-fi sagas should probably take note.

Canon as we know it is a relatively new concept. When "Doctor Who" and "Star Trek" debuted in the 1960s, even the most forward-thinking writers would never have dreamed their ideas would still be impacting popular culture six decades later. There was no grand plan for the future — the Doctor wasn't revealed to be a Time Lord until the show was six years old — and the creatives were often making things up as they went. "Who" continuity remains a notoriously nebulous concept.

And despite George Lucas's earlier plans for the "Journal of the Whills", the original "Star Wars" trilogy was effectively a blank slate, in which he was free to tell any story he wanted. Even the prequels had minimal existing lore to dodge, with the numerous novels, comics and cartoons of the Expanded Universe occupying lower tiers of canon — pre-Disney, only the movies (and, to a lesser extent, the CG "Clone Wars") were gospel.

Even so, Lucas's reliance on the "from a certain point of view" principle still managed to wind up a significant portion of the fanbase. Why would Obi-Wan describe Yoda as "the Jedi Master who instructed me" if Qui-Gon Jinn was his teacher? How did Princess Leia remember her mom if Padmé died when she was just a few minutes old?But canon's a minor inconvenience when you're only dealing with a few movies. It's when you move into vast multimedia empires, straddling numerous interconnected films,TV shows, books, comics and cameos in "Fortnite" that it becomes a potential stumbling block.

Firstly, there's the heritage factor, as "Star Wars", "Star Trek", "Doctor Who" and every other legacy franchise have decided that nostalgia is their not-so-secret weapon. Often the impact is minimal — bringing one-off "Star Trek" character Roger Korby into prequel show "Strange New Worlds", for example — but leaning into existing canon can sometimes be a plotline's entire raison d'être.

Han Solo's sub-12 parsec Kessel Run was a casual, slightly nonsensical aside until it became a major set piece in "Solo: A Star Wars Story". Meanwhile, Omega (the Big Bad in the most recent "Doctor Who" finale) hadn't appeared on screen since 1983 Fifth Doctor story "Arc of Infinity" — a deep cut for all but the most hardcore of fans.

Much worse, however, is persisting with plotlines that don't work. Few TV shows get everything right from day one, and any long-running series will have — in fact, should have — some less successful stories in the back catalogue. It shows that they're trying to push the envelope, rather than just sticking to a formula.

Sometimes a franchise can make a minor course correction — the Leslie Knope of "Parks and Recreation"'s second season was subtly different to the Leslie Knope of the first — but other times it's best to just hold up your hands and consign an idea to the trash.

This is why we're unlikely to ever see anyone following in Tom Paris and Kathryn Janeway's footsteps by breaking the warp-10 barrier and turning into giant lizards, as they did in the infamous "Star Trek: Voyager" episode "Threshold". Writer Brannon Braga later described the story as a "royal, steaming stinker" and it was rumored to have been excised from canon. For similar reasons, the revelation that the Doctor is half-human on his mother's side has been conveniently brushed under the carpet since its one and only mention in the 1996 "Doctor Who" TV movie.

Arguably the smartest thing about "Alien: Earth" is the way Hawley's been picky about the essentials. Even the franchise's most strident fans would probably admit there hasn't been a significant addition to Xenomorph mythology since the Alien Queen reared her ugly head in "Aliens", four decades ago. But the decision to turn the TV show into a drama about child androids, feuding corporations and — crucially — an all-new menagerie of bizarre "Thing"-inspired fauna has given a 46-year-old saga a new lease of life, rather less reliant on its eponymous star beast — even Ridley Scott admitted after "Covenant"'s disappointing box office performance that, "I think the beast has almost run out, personally."

Cleverest of all, "Alien: Earth" has followed its path without (as yet) directly contradicting anything that's gone before, instead being selective about what to include and what to ignore. Anything that didn't make the cut? Well, maybe that's happening in a distant star system, on the other end of a lengthy voyage in hypersleep. (Or maybe it didn't happen at all.)

"Star Wars", "Star Trek", "Doctor Who" and the rest should all be watching with interest, because when you've got one eye on the past — even a freaky alien one with legs — it's hard to truly embrace the future. And besides, none of it is real anyway.

The final episode of "Alien: Earth"'s first season streams on Disney+ starting Wednesday Sept. 24.

That was the core, mind-boggling question behind a Sept. 9 congressional House of Representatives hearing, held by the Task Force on the Declassification of Federal Secrets.

Representative Anna Paulina Luna (R-FL) is chair of that task force, swearing in witnesses that under oath discussed their experiences and knowledge about UAPs, a rebranded term attached, deserved or not, to unidentified flying objects (UFOs), as well as unidentified objects or phenomena in Earth's bodies of water or space.

Secrecy, stigma, dismissal

For too long, UAPs have been "shrouded in secrecy, stigma, and in some cases outright dismissal," Luna said in her opening statement.

"Today, I want to state clearly: this is not science fiction or creating speculation. This is about national security, government accountability, and the American people's right to the truth," said Luna. "Future generations will look back on this moment and ask what we did when presented with the unknown. Did we look away, embarrassed or afraid? Or did we pursue the truth with courage? I intend to be on the side of truth, transparency, and accountability," the lawmaker stated.

A transcript of the hearing and witnesses' prepared testimonies can be read on the U.S. House of Representatives' website.

Space.com asked several experts from leading research groups on UAPs/UFOs concerning the hearing and their take-away thoughts.

Wanted: nitty-gritty details

"The military witness reports were very good," said Robert Powell, executive board member of the Scientific Coalition for UAP Studies in Austin, Texas.

While it may not be apparent to the public or congress, Powell said that anyone who has studied the history of the subject knows that there have been hundreds of such reports by military witnesses that are equally as good.

So how do we move forward?

"Unless Congress is willing to push for the nitty-gritty details" by obtaining full videos, interviewing pilots involved in UAP incidents, and other reported events, "we will not progress," said Powell.

Powell said, in his view, the military will never release the necessary information to establish the presence of a non-human intelligence.

"That's because of their concerns for national security and whether one of our adversaries might learn something from UAP that they could use militarily against us," Powell said. "The resulting tendency to silo all information on UAP prevents moving forward with learning more. Only if Congress allocates funding to the scientific community and academia to study UAP will we make any progress," he concluded.

Science above all

"I find it frustrating that they, rightly, reiterate the importance of the role science can take in figuring out what is behind UAP, but do not apply it in these hearings."

That's the outlook from Alejandro Rojas, a long-time UFO journalist and a consultant to Enigma, a UAP/UFO sightings alert network.

"We have years of anecdotal sighting reports and claims of hidden government knowledge about alien visitation. What we need is evidence," Rojas said.

Rojas added that he found it also trying that the one organization that has been using science, the Pentagon's All-domain Anomaly Resolution Office (AARO), was pummeled in the hearing, without being represented.

"Having worked in the UFO field for so long, I am sympathetic to their [AARO's] effort. They have shown each step of their work analyzing previous videos, and although it is unpopular to demystify some of these reports, their scientific analyses have been sound," he said.

Preconceived notions

At the recent hearing, "the gripes of committee members came across as being frustrated with the organization that is using science and coming up with answers," sensed Rojas. "However, because they dislike the answers, they blame AARO, when in fact they genuinely do not want scientific analysis to dismantle their preconceived notions."

In the end, Rojas found the hearing disheartening.

"Instead of focusing on real issues and truly championing scientific investigation, the hearing comes across as a very political back-and-forth between the Oversight Committee and the Pentagon," said Rojas. "What gets lost is what we actually need, and that is data gathering and scientific evaluation of that data."

As a consultant with Enigma, Rojas said the group is collecting hundreds of reports, many with videos.

"What we need is a robust, transparent effort to analyze what we are collecting, and to build better sensor systems to gather more and better data on UAP," said Rojas. "If extraterrestrials are visiting us, it is not just the military that would be seeing them."

Credible and intriguing

Avi Loeb, head of the Galileo Project at Harvard, and director of the Institute for Theory & Computation, said he found the first-hand testimonies at the hearing "to be credible and intriguing."

Loeb's Galileo Project is an endeavor to bring the search for extraterrestrial technological signatures of other star folk from "accidental or anecdotal observations and legends" to the mainstream of crystal-clear, confirmed and systematic scientific research.

"I salute congresswoman Luna for chairing this important discussion within the Task Force on the Declassification of Federal Secrets in the U.S. Congress," Loeb said.

But does such a congressional hearing restore public interest in UAP?

"This discussion is not a matter of public relations in a popularity contest, but instead a topic of great relevance for national security and science," responded Loeb. "Once we all see credible evidence about the nature of UAP, we will be able to get to the bottom of it and everyone would agree on what it means."

Best path to new knowledge

Data collection is the goal of the Galileo Project under Loeb's leadership.

Does the astrophysicist believe that the U.S. government is hiding information? He replied that "as a scientist I respond to evidence and not to what people tell me. Scientific evidence is our best path to new knowledge."

The simplest way to tell the difference between a dogmatist and a genuine scientist, Loeb said, is to flood both of them with scientific-quality data.

"Whereas the dogmatist will shove anomalous data under the carpet of traditional thinking, an open-minded scientist will be thrilled to learn something new with an underlying sense of humility," advised Loeb. "Not only is nature more imaginative than we are, but it also does not care whether we figure it out. The insistence that everything in the sky is either icy rocks or human-made technologies will not rid us of cosmic neighbors, if they exist out there," he concluded.

Tone and testimony

"Overall, I was pleased with the tone and testimony in the hearing from the witnesses, and the often excellent questions from the Representatives," said Mark Rodeghier, president and scientific director of the Center for UFO Studies in Chicago, Illinois.

"The hearing hopefully provided more impetus to pass the crucial legislation necessary to answer questions we have about possible US government/contractor involvement with UAP that has been hidden all these years," said Rodeghier.

Rodeghier said the witnesses added additional experiences on the record of both UAP sightings and how the aftermath of those has been handled by the military, including treatment of those wishing to speak publicly.

Crucial legislation

Beyond moving Congress to pass the bills, Rodeghier advised getting witnesses into a SCIF, short for Sensitive Compartmented Information Facility. Located several levels beneath the U.S. Capitol, a SCIF is where lawmakers and witnesses hold closed interviews, far from the prying eyes of the public.

"I'm not sure what can be done with it [those interviews], but having it available is important," said Rodeghier.

Another Rodeghier recommendation is to have the head of AARO in a hearing this fall now that he has been on the job for a year. Lastly, there's need to work on getting the appropriate government agencies to provide modest funding for UAP research, which continues to be unavailable, he said.

Deep difficulties

Michael Cifone is the founding executive director of the Society for UAP Studies, based in Los Angeles, California. The group's mission is not to promote a single narrative but to advance careful scholarship, develop educational frameworks, and advocate for standards of evidence and data transparency.

The recent Congressional hearing on UAPs underscored, once again, "both the importance of the issue and the deep difficulties that have hampered its treatment for decades," said Cifone.

That handling of the topic within the government — whose aim since at least after World War II has been increasingly obsessed with national security and maintaining US military and strategic dominance, feels Cifone, "are guiding principles that are ultimately at odds with the inner operating directives of the sciences themselves: free, open, and therefore democratic exploration of self and world."

Mixed pool

"The UAP problem is not a mystery with one answer, but rather a somewhat unstable and chaotic amalgam of many overlapping realities, complicated by the unfortunate facts of the modern bureaucratic national security state," is a view that Cifone basically endorses.

"UAP reports are not a monolith," Cifone advised.

Instead, they are a mixed pool consisting of: (1) misidentified U.S. black projects, where cutting-edge aerospace programs are understandably shrouded in secrecy; (2) adversarial drones and surveillance platforms, which represent a genuine national security challenge; (3) a large number of ordinary misperceptions of balloons, satellites, or atmospheric phenomena; and (4) a small but stubborn residue of anomalous cases that resist explanation.

"This mixture makes the phenomenon difficult to study, not because of some grand cover-up, but because of the dysfunctional way information is handled inside the government," Cifone said.

Are we up to the task?

The UAP hearing, for all its frustrations, said Cifone, "at least signaled that Congress is beginning to take seriously the structural problems that have long clouded this issue."

From a safety standpoint, the "mixture hypothesis" is particularly important, said Cifone. If even a fraction of UAP reports involve advanced adversarial drones or unsafe incursions into U.S. airspace, then society is faced with an aviation and national security challenge that demands systematic response, he said.

"Let's see what data and frameworks we can establish that can handle UAP and associated phenomena/claims, and what philosophical/conceptual challenges remain, and if we're up to the task," Cifone said.

And for the other claims — crashes, bodies, and so on, Cifone concludes, "sure, but where's the beef?"

That strong, baffling radio episode was captured by Ohio State University's Search for Extraterrestrial Intelligence (SETI) project, also known as the "Big Ear." It has been viewed by some as one of the oddest radio transmissions from afar ever detected, also cited as compelling evidence for extraterrestrial intelligence.

The outburst was a strong narrowband radio signal received on Aug. 15, 1977 by Ohio State University's Big Ear radio telescope. Astronomer Jerry Ehman discovered the anomaly a few days later while reviewing the recorded data — writing on a computer printout "Wow!"

Unpublished observations, archival data

Jump ahead to today. Researchers from the Planetary Habitability Laboratory at the University of Puerto Rico at Arecibo are proposing a less extraterrestrial explanation. On-going assessments, led by Abel Méndez, are being pursued under the "Arecibo Wow!" Project, an initiative established to analyze unexplained radio signals from space in the search for extraterrestrial intelligence.

"We look at old archives with modern science methodologies. It's a bit like space archaeology," said Wow! Signal researcher Hector Socas Navarro, director of the European Solar Telescope Foundation and a staff scientist at the Instituto de Astrofísica de Canarias.

New clues

Researchers from that project have re-analyzed decades of previously unpublished observations and archival data from the Ohio State University SETI program. The result is the most precise characterization yet of the perplexing signal from afar and revealing new clues to its origin.

"Our newly derived properties may help finally pinpoint the source of the Wow! Signal," Méndez told Space.com. While the group's just-published paper focused on revising the known properties of the Wow! Signal, "we also discovered new properties that we look forward to sharing in an upcoming paper," he advised.

"We aim to archive and share all data from the Big Ear telescope by 2027, marking the 50th anniversary of the Wow! Signal," Méndez added.

Natural astrophysical origin?

In a recent posting on the Arecibo Wow! Project's website, Méndez underscored the team's output to date.

The research findings spotlight the prospect that the Wow! Signal was created by a natural astrophysical origin, Méndez and colleagues report. Also the work does make radio interference "an increasingly unlikely explanation," they add.

"This study doesn't close the case," Méndez points out. "It reopens it, but now with a much sharper map in hand."

Méndez and fellow researchers hypothesize that the Wow! Signal was caused by a sudden brightening of the hydrogen line in interstellar clouds, triggered by a powerful transient radiation source such as a magnetar flare or soft gamma repeater (SGR).

"Our results don't solve the mystery of the Wow! Signal," Méndez states. "But they give us the clearest picture yet of what it was and where it came from. This new precision allows us to target future observations more effectively than ever before."

Citizen science — join the search

The continuing research into the Wow! Signal has spurred the creation of the Wow@Home project. This initiative is a low-cost way that others can now actively search for similar signals and other rare cosmic events, including potential technosignatures of other star folk — in real time.

Wow@Home project officials found that the Wow! Signal was strong enough that even small telescopes could potentially detect similar signals.

Indeed, a network of small radio telescopes offers several distinct advantages compared to large professional observatories.

Low-cost systems can operate autonomously around the clock, "making them ideal for continuous monitoring of transient events or long-duration signals that professional telescopes cannot commit to observing full-time," Méndez and colleagues suggest.

Wow-like signal strength

Wow@Home is a cost-effective, engaging, and accessible, ideal for education, citizen science, and expanding participation in radio astronomy.

"A complete setup costs around $500, including a dedicated computer, but we are not selling these systems. Instead, we will provide recommendations for the necessary parts and offer free software to power the telescope and connect it to the Wow@Home network to search for transient events," a Wow@Home posting explains.

The software is built on analysis methods the project's developing to detect Wow-like signals in the archive data of professional observatories, as part of their Arecibo Wow! undertaking.

For more information on Wow@Home, visit the project's website. The group's recent research report is available on arXiv.org and will be submitted to the Astrophysical Journal.

Who's just a wee bit curious to discover exactly what's inside that crashed extraterrestrial mothership in Apple TV+'s riveting sci-fi show, "Invasion"? Yeah, us too.

After 2023's season 2 cliffhanger finale, that titanic derelict craft is just waiting to be investigated and, as this haunting new season 3 trailer shows, our international band of hardy survivors facing humanity’s extinction seems up to the task.

"Invasion" and its latest 10-episode outing lands back on Earth on Friday, Aug. 22, 2025, with a single episode premiere, followed by new chapters rolling out weekly each Friday until its Oct. 24, 2025, conclusion. This series has evolved into one of the finest offerings in Apple TV+'s extensive lineup of sci-fi sensations that also includes "Foundation," "Silo," "For All Mankind," and more. We can't wait to creep inside the behemoth spacecraft to explore.

Executive produced by Oscar-nominated and two-time Emmy-nominated filmmaker Simon Kinberg ("Deadpool," "X-Men: Days of Future Past," "The Martian") and David Weil ("Hunters"), "Invasion" season 3 will step into the unknown with the series' main group converging to devise a plan that will see them infiltrate the intimidating aliens fallen headquarters.

With the infestation of shapeshifting hunter-killers spreading across the globe, randomly slaughtering humans like cattle, these diverse strangers must forge a bond as they struggle to uncover a weakness in these uninvited creatures before time runs out.

In this enticing trailer, we see an elite crew of commandos formed to cross through the dead zone towards the wreckage of the downed mothership on a predictably doomed helicopter flight, with our connected heroes reluctantly recruited to join the team due to their psychic link to the aliens. We’re also treated to some unsettling imagery of crawling luminescent creatures inside their dark lair, showing the hidden horrors that have obviously evolved into more insidious lifeforms.

"What I saw is new, more powerful," reveals Shamier Anderson's Trevante. "And they’re not done."

"Invasion" season 3 arrives Aug. 22 exclusively on Apple TV+ with familiar returning faces that include actors Golshifteh Farahani, Shioli Kutsuna, Shamier Anderson, India Brown, Shane Zaza, and Enver Gjokaj. This season also introduces new series regular Erika Alexander.

While 'solo' Predator and Alien flicks were having some downtime in the 2000s, both franchises were kept alive with comic books, video games, and the two divisive Alien vs. Predator movies. The extended universe that surrounded the series grew much larger, and we got excellent games like Rebellion and Monolith's Aliens vs. Predator first-person shooters. Hot on the heels of those two and the first AvP movie, developer Eurocom got the chance to make a standalone Predator title targeting the 'ultimate alien hunter' power fantasy.

Though it never escaped PS2 and Xbox following bad reviews, Predator: Concrete Jungle gained a cult following, as no other Predator game had offered that gory action-adventure single-player experience that fans craved. It told an ambitious — and often silly — story full of twists and turns that made even Dark Horse's loopiest comics seem predictable.

With Badlands just around the corner, we revisited this overlooked 2005 game release and found more than one or two common points that suggest Trachtenberg has been digging deep into the franchise's history for his grand ideas.

Yautja outcasts

The most obvious connection is found in Badlands' Yautja protagonist, Dek. He's described as a young hunter who is an outcast after he fails his clan in some way. Now he's on a quest to regain his honor by hunting "the ultimate adversary" on a remote and ruthless planet. We've yet to learn more about the actual plot once the adventure gets going, but the setup alone instantly evokes Concrete Jungle's.

In Eurocom's game, a Predator nicknamed 'Scarface' is badly wounded by the mob in the year 1930 in New Way City. As a last resort, he sets off the self-destruct device we first saw in the original movie. While much of the city and his ship are destroyed, he fails to kill himself and protect Predator technology from reaching human hands, which leads to his clan exiling him to a desolate planet where insect-like creatures are at the top of the food chain.

There are some differences between the two stories, most notably in the time period they're set in. Concrete Jungle's story picks Scarface back up 100 years after the prologue — around 2030 — while Badlands is set much further into the future (we don't know the exact year, but humanity has space travel, synthetics, and terraforming courtesy of Alien's Weyland-Yutani).

Ultimately, Concrete Jungle is a story of redemption and humans messing with forces they don't understand. It echoes Prometheus and the "secret fire from the Gods" themes, beating the first of Ridley Scott's Alien prequels to the punch by over half a decade.

Predator: Badlands' Yautja lead is more of a rookie who will also have an unexpected synth ally, but we could see similar character arc and story beats throughout the film. Let's just hope the movie's 'final boss' will be more convincing than a human-Predator hybrid (yes, really).

The Alien connections

We know that the Weyland-Yutani corporation is present in Predator Badlands, marking the first step towards an inevitable Alien vs Predator crossover, but Concrete Jungle was out there name-dropping the Weyland Corp 20 years ago. At first glance, the game looks like an homage to Predator 2 with a cyberpunk twist, but things escalate quickly with a surprising tie-in to the previous year's Alien vs Predator movie.

The Xenomorphs appear as late-game foes in Concrete Jungle without much explanation as to their presence on Earth, but writer Grant Morrison (yes, comic book legend Grant Morrison) slips in a quick reference to Charles Bishop Weyland and his disappearance that heavily implies we're in the same universe as the movie. Perhaps Borgia Industries — the ruling corporation in Neonopolis following the 1930 disaster — picked up the Alien queen from the Antarctic waters?

The surprises keep coming in the closing moments, when a second Weyland appears and mentions the Yutani Corporation — we're pre-merger at this point, something Alien: Earth will also touch upon.

But perhaps the wildest reveal is that Isabella Borgia — a character from the prologue — shows up 100 years later, having apparently gained immortality after being covered in Predator blood. After Scarface takes her down, Weyland recovers her brain and jams it into a supercomputer. A supercomputer called MOTHER.

Predator: Concrete Jungle ended up being a stealth Alien prequel in many ways. The movie Aliens vs. Predator: Requiem would try a similar move with its cliffhanger ending and recovered Predator tech roughly two years later, but neither is, at least right now, considered canon. Despite that, Predator: Badlands is clearly establishing solid links between the two franchises, and rumors are floating around that a Predator will show up in the Alien Romulus sequel.

Whatever ends up happening in Predator: Badlands, it's clear that the 'powers that be' over at 20th Century Studios have been digging deep for inspiration, scouring the rich canvas painted by not only the Predator movies, but also comic books and video games over the years This might be the (conceptual) key to success filmmakers had been searching for, and we're delighted to see Trachtenberg and his peers leaning on often ignored works to boldly expand the series' cinematic possibilities.

Predator: Concrete Jungle is available to play on PS2 and Xbox if you're lucky enough to find a copy second-hand. Predator: Badlands will release in theaters on November 7, 2025. You can watch the rest of the franchise on Hulu (US) or Disney+ (UK).

"Alien: Earth" is landing soon.

From the stimulating looks of this bloody-good new trailer for the 8-episode "Alien: Earth" series from "Fargo" creator Noah Hawley's, the visionary filmmaker has no hesitation to terrify viewers when the ambitious sci-fi series hatches on FX and Hulu starting on Aug. 12, 2025.

Starring Sydney Chandler, Alex Lawther, Timothy Olyphant, Essie Davis, Samuel Blenkin, Babou Ceesay, David Rysdahl, Adrian Edmondson, Adarsh Gourav, Jonathan Ajayi, Erana James, Lily Newmark, Diem Camille, and Moe Bar-El, "Alien: Earth's" horrifying events play out in the year 2120 when the USCSS Maginot, a Weyland-Yutani deep space research spaceship, crashes on Earth in Prodigy City custodian of five deadly extraterrestrial lifeforms collected "from the darkest corners of the universe."

The plot focuses on Wendy (Chandler), a Prodigy Corporation-made humanoid robot synthetic and her hybrid tactical team that are dispatched to explore the crash site, search for survivors, and recover escaped specimens  —  including the notorious alien predator we all know as the eyeless, acid-spewing xenomorph.

"We don't lock them down … it will be too late," Timothy Olyphant's character Kirsh declares in the trailer. This atmospheric preview titled "Greener World" and paired with the somber song "A Greener World" by Gwilym Gold gives us a disturbing glimpse in the android-obsessed, corporate-run world of the 22nd century on Earth and the haunted house-like ship interiors. The final image of a dome-headed xenomorph crouching outside a forest cave is chilling!

"Alien: Earth" lands on FX and Hulu Aug. 12 and is executive produced by Noah Hawley, Ridley Scott, David W. Zucker, Joseph Iberti, Dana Gonzales and Clayton Krueger.

While the world-invasion types tend to grab the headlines with stunts like demolishing popular tourist destinations ("Independence Day") and vaporising the populace with death rays ("Mars Attacks!", "War of the Worlds"), the friendly aliens who come in peace are more likely to embrace humanity for all its flaws. Indeed, the 13 extra-terrestrials below have almost invariably left the world better than they found it, whether it's by saving the day, being an entertaining house guest, or expanding the fundamental limits of human consciousness.

So, with the live-action "Lilo & Stitch” remake and 'Elio’ now in cinemas, we celebrate a baker's dozen of pop culture's most memorable alien visitors, ordered by the date they first made contact with the people of Earth. And we also bring a warning from the cosmos — you may have a close encounter with a plot spoiler or two.

Superman (aka Kal-El)

• As seen in: numerous comics, movies and TV shows, including James Gunn's upcoming "Superman" movie
• Date of first contact: 1938

Few alien visitors have embraced Earth culture quite as readily as the son of Jor-El, who's spent a large chunk of his superhero career espousing values of "truth, justice, and a better tomorrow" (formerly "the American way"). Thanks to the effects of Earth's yellow sun on his Kryptonian physiology, Superman's enhanced strength, eye lasers, and ability to fly — not to mention his penchant for wearing his underwear outside his clothes — make him stand out from the crowd. Indeed, several recent stories (including the 2013 movie "Man of Steel") have explored how the world regards an alien who acts as a self-appointed peacekeeper.

But despite his unwavering devotion to protecting those in need — ignoring that bit in "Superman III" when he grew designer stubble and went bad — you can't help thinking he'd rather be settling down as Clark Kent, living out his happy-ever-after with Lois Lane.

Other friendly aliens from the DC stable include Supergirl, Martian Manhunter, and various members of the Green Lantern Corps.

Glordon

• As seen in: "Elio"
• Date of first contact: 2025

His dad, Lord Grigon, may be a power-hungry warlord with aspirations of seizing the peaceful Communiverse by force, but Glordon has no intention of joining the family business. He's certainly sceptical about spending the rest of his life in a robotic carapace, even though he'll be getting a state-of-the-art model featuring sophisticated weaponry, a lighter, and a cup holder.

A friendly, trusting demeanour makes this extra-terrestrial cross between a worm and a tardigrade the perfect best friend for Elio Solis, a human boy masquerading as Earth's ambassador to the cosmos. Sure, using his homespun silk to wrap Elio in a cocoon feels like an awkward way to say hello — especially for anyone who's seen Shelob in "The Lord of the Rings" — but there's no question the gesture comes from a good place.

Glordon wholeheartedly embraces his role as a "bargaining chip" in Elio's negotiations with his father, and besides, who wouldn't want a bestie who's not only fireproof, but also prepared to welcome you into his giant mouth whenever a river of lava heads your way?

Klaatu

• As seen in: "The Day the Earth Stood Still"
• Date of first contact: 1951

These days the poster for the original "The Day the Earth Stood Still" would probably be called out for false advertising. Giant robot Gort can be seen carrying a scantily clad woman while firing a laser from his eyes, recreating a scene that never actually happens in the movie.

Instead, Gort's boss, Klaatu (Michael Rennie), really does come to Earth "in peace and with good will", but ends up getting shot after a nervous soldier misunderstands his motives. In a highly topical move, Klaatu warns Earth's governments that the development of nuclear weapons has made the galactic community antsy, and subsequently turns off everybody's electricity for half an hour to prove he's not playing games. Of course, his message doesn't get across to everybody, and plenty see Klaatu as an interstellar busybody. Nobody can claim, however, that he didn't have our best interests at heart.

Keanu Reeves played Klaatu in a disappointing 2008 remake. Klaatu's famous catchphrase — "Klaatu barada nikto" — also inspired the names of several aliens in the "Star Wars" universe.

The Doctor

• As seen in: "Doctor Who"
• Date of first contact: 1963

Like Superman, the Doctor has devoted much of their professional life (or should that be lives?) to protecting the people of planet Earth. Every single one of the Time Lord's regenerations has displayed an uncanny knack for tracking down trouble, and doing what's necessary to sort it out — whether it involves a sonic screwdriver, reversing the polarity of the neutron flow, or some old-school monologuing. This modus operandi is a direct contravention of Gallifrey's strict non-interference policies.

But, given the unlimited wonders accessible to the owner of a TARDIS that can traverse all of space and time, the Doctor's ongoing obsession with Earth and its people (particularly the UK) seems slightly incongruous. Modern incarnations even manage to keep up with contemporary popular culture, particularly impressive for someone who's well over a thousand years old.

Unnamed alien visitors (Close Encounters of the Third Kind)

• As seen in: "Close Encounters of the Third Kind"
• Date of first contact: 1977

The most famous friendly alien to debut on the big screen in 1977 was undoubtedly Chewbacca but, seeing as everybody in "Star Wars"' galaxy far, far away is technically an extra-terrestrial, he doesn't really warrant a place on this list. The aliens from that year's other timeless sci-fi classic most definitely do, however, because this unnamed race of interstellar travellers arrive on Earth with an agenda of friendship, and a natural instinct for the theatrical.

Over the course of Steven Spielberg's movie, UFO sightings, toys coming to life, and visions of Devils Tower in Wyoming (subsequently recreated in mashed potato) gradually evolve into something more spectacular. The aliens' perfectly choreographed introduction culminates in a spectacular light show, accompanied by a musical symphony riffing on the most famous five notes in movie history. All in all, it's an extremely memorable way to say hello.

ET (aka The Extra-terrestrial)

• As seen in: "ET: The Extra-Terrestrial"
• Date of first contact: 1982

In the early stages of its development, "ET" was going to be alien visitation horror, but Steven Spielberg eventually changed tack to tell cinema's most beloved tale of a friendly alien coming to stay.

The movie's narrative drive comes from the marooned ET's efforts to "phone home", but it's his relationship with 10-year-old Elliott (Henry Thomas) and siblings Gertie (Drew Barrymore) and Michael (Robert MacNaughton) that provides the emotional punch. ET throws himself into Earth culture, watching daytime TV and bingeing fizzy drinks, while also bringing alien superpowers like instant healing and bike levitation to the party. All good reasons why there's not a dry eye in the house when he finally blasts off.

"Mac and Me" (1988) explored similar themes with more Happy Meal product placement, while John Carpenter's "Starman" (1984) did "'ET' for grown-ups" when Jeff Bridges' alien took the form of Karen Allen's late husband.

The Antareans

• As seen in: "Cocoon"
• Date of first contact: 1985

If "ET" was the quintessential alien movie for kids, "Cocoon" put a senior-friendly spin on visitors from outer space. In Ron Howard's film, a delegation from the planet of Antarea head to Florida to rescue some long-lost compatriots who've spent the last 10,000 years cocooned at the bottom of the Atlantic. Before heading home, they plan to replenish them in a swimming pool supercharged with special life force, but don't bank on a bunch of residents from a nearby retirement home taking unauthorised dips and rediscovering their youth.

The Antareans — luminescent beings of light beneath their human disguises — are surprisingly tolerant of the trespassing, even though it completely messes up the cocoons' recovery. They even agree to take the sprightly OAPs back to their homeworld for a shot at eternal life.

Contact aliens

• As seen in: "Contact"
• Date of first contact: 1997

You'd expect a film based on a novel by Carl Sagan to take a thought-provoking approach to aliens, and "Back to the Future" director Robert Zemeckis's adaptation does just that. SETI scientist Dr Ellie Arroway (Jodie Foster) picks up a radio signal from the star Vega, and realises it contains detailed instructions for building a machine that will allow one person to travel across the cosmos.

This being the Hollywood version of science — and despite the reservations of Matthew McConaughey's preacher — Arroway is also the person chosen to represent humanity on the maiden voyage. After reaching her destination, she meets an alien who's taken the form of her late father (David Morse), and tells her the sophisticated ETs got in touch to welcome humanity into the wider universe. Unfortunately, Arroway has no evidence of the meeting when she returns.

E 626 (aka Stitch)

• As seen in: "Lilo & Stitch"
• Date of first contact: 2002

Don't let Experiment 626's Disneyfied cuteness fool you. This alien was genetically engineered by morally dubious scientist Dr Jumba Jookiba as a super-intelligent weapon of mass destruction. When it escapes from exile, the creature crashes in Hawaii and goes incognito as a dog in an animal shelter — which is where he first meets a young orphan called Lilo.

Lilo names the creature Stitch and, realising that he's no ordinary dog, she attempts to domesticate a "pet" who causes constant (but comedic) disruption at home. Before long, however, a growing friendship gradually overcomes Stitch's more destructive instincts, and the titular duo form a tight partnership — which is for the best, seeing as Stitch remains a fugitive from the United Galactic Federation (not the one from "Star Trek").

Prawns

• As seen in: "District 9"
• Date of first contact: 2009

The aliens in "District 9" — pejoratively described as "Prawns" by the humans in the film — possess space-faring technology way beyond our own. Even so, when their ship arrives over Johannesburg in the early 1980s, the South African government immediately decides they're second-class citizens and relocates them to a camp called District 9. Lowly Department of Alien Affairs official Wikus van de Merwe (Sharlto Copley) is, like most humans, suspicious of the alien visitors, but forms an unlikely friendship with District 9 resident Christopher Johnson (Jason Cope) after he's infected by some alien goop.

Johnson may look like the product of Seth Brundle's experiments-gone-wrong in "The Fly" but he's also a very relatable dad trying to do the right thing for his son — and arguably much more sympathetic than any of the humans in the movie.

Paul

• As seen in: "Paul"
• Date of first contact: 2011

From "The X-Files" and "Dark Skies" to "Close Encounters of the Third Kind", plenty of TV shows and movies have riffed on the classic Roswell image of grey aliens with big black eyes. Few, however, have done it quite as successfully as "Paul" — the film even features a flashback to eponymous alien Paul (Seth Rogen) giving tips to a pre-"ET" Steven Spielberg, while sitting in an Area 51 warehouse that looks just like the one from "Raiders of the Lost Ark". Essentially, he claims to be the inspiration for some of the biggest sci-fi properties of the last 50 years. He even invented Fox Mulder.

Pop culture influences aside, Paul has refused to turn bitter despite the US government holding him hostage since his spaceship crashed in 1947. All these decades later he just wants to go home, and at heart is just a really good guy.

Heptapods

• As seen in: "Arrival"
• Date of first contact: 2016

"Star Trek" (a franchise that has plenty of friendly aliens of its own) has popularised the idea that most extra-terrestrial species look like humans — there's even an episode of "The Next Generation", "The Chase", that explains why Vulcans, Klingons, Cardassians and most other residents of the Alpha Quadrant look so alike. But in "Arrival" (based on Ted Chiang novella "Story of Your Life"), the heptapods who pay Earth a visit are so alien that we have to take a whole new approach to communication.

With governments and the military as sceptical as ever about the new visitors — have they learned nothing from "The Day the Earth Stood Still"? — linguist Louise Banks (Amy Adams) gradually cracks the heptapods' pictogram-based code. The aliens' language actually shifts the "speaker"'s perception of time, giving Banks spookily realistic premonitions of a daughter who hasn't yet been born, while offering the promise of a whole new frontier for humanity. Duolingo has a long way to go…

"Harry Vanderspeigle"

• As seen in: "Resident Alien"
• Date of first contact: 2021

It may not be immediately obvious, but "Harry Vanderspeigle" (his real alien name is tricky for humans to pronounce) has something in common with the aforementioned Stitch. Like the artist formerly known as Experiment 626, his original assignment involved destruction — namely, the elimination of the entire human race. But, after assuming the identity of a human doctor, getting some ad hoc medical training from "Law & Order", and setting up shop in a small Colorado town, this would-be space invader gradually comes to realise that, just maybe, we aren't so bad after all.

Harry's natural bug-eyed form suggests he's a fairly close relative of Paul, though he's able to adopt the very convincing disguise of genre legend Alan Tudyk ("Firefly", "I, Robot", "Rogue One").

If you want to meet a friendly alien yourself, the live-action Lilo and Stitch and Elio are in theaters now, and Superman will be in theaters in July.

His upcoming science fiction novel, "Hole in the Sky," lands on Oct. 7, 2025, from his longtime publisher, Doubleday. It depicts a most unusual alien first contact event on a Cherokee Indian reservation in Oklahoma, and has already been snapped up by Netflix and Aggregate Films for a feature film. Wilson will also act as an executive producer and adapt the screenplay from his own book.

Hollywood has a real appetite for Wilson’s brand of storytelling, and the Portland-based writer has at least a half-dozen Tinseltown projects in various stages of development.

"I had a book come out right when COVID started, so I switched over and started writing screenplays and television for a few years," Wilson tells Space.com. "Then we had a big strike, and so there was a great time to put on my novelist hat and go back and write a book. This really digs into two of my favorite things: where I’m from in Oklahoma, and robots and science fiction. I was really inspired to have a native take on first contact. You see so many alien invasion movies, and they’re really a dark reflection of what colonizers have already done to indigenous people. The aliens show up, and it’s like fear projection. They enslave people, they extract our resources, they destroy our monuments and our culture. It’s kind of the same story."

Wilson's thought process while composing this extraterrestrial arrival tale was focused on what the native perspective would be on the unknown, particularly the Cherokee perspective since he was raised in what's now the Cherokee reservation in North Tulsa.

"I'm a Cherokee citizen and I spent the summers with my grandparents on our original land allotment,” he explains. "It was about a mile or so away from this place called Spiro Mounds, which is the westernmost outpost of the Mound Builder civilization that disappeared thousands of years ago. But they've left these mounds all over the United States, and it's this ancient and mysterious place. Those tribes were the precursor tribes to all the tribes we know now.”

"Hole in the Sky" starts out with NASA's first observation of an interstellar object with its rapid approach and an impact on Earth that results in first contact.

"It's told through the lens of a by-the-books CIA weapons expert, the sort of person you'd expect to deal with this stuff, an anti-social NASA astrophysicist, and a really determined Cherokee father who lives in the place where this happens," Wilson adds. "All of these characters have a different perspective on the unknown. Typically, scientists want to understand it. Usually, they want to exploit it. Soldiers are afraid of the unknown, they want to destroy it. My native characters are comfortable with it. This guy lives with the unknown in his backyard. That was fun to tell that story and get to subvert that genre and put my own spin on first contact."

Mound Builders had a massive civilization on the scale of the Mayans, mainly in the Eastern portion of the United States. These earthworks were created anywhere it was useful to have a city, a place that had commerce and was easily defensible. As a result of these ancient people’s engineering, many mounds were eventually bulldozed over and major cities built atop them.

"We're talking about ten or fifteen thousand years ago, which plays into the story," says Wilson. "There's a lot of looking back to look forward. I ended up thinking a lot about what is indigenous technology. Right now, in Oregon, Washington, and California, they’re looking back at the way indigenous people dealt with their forests to prevent forest fires. They're trying to find that old knowledge to apply it now."

Netflix and Jason Bateman’s Aggregate Films were offered a draft of Wilson's book while the author and his agent pitched both the novel and the screenplay, which prompted constructive feedback that altered some elements of the story.

"I found the process really fun because film is so visual and you're thinking about how to make it super visual, and some of that can go into the book," he notes. "But in the book, you can go straight into people's heads and get into what they’re thinking. That’s something that’s harder to do in a film and get all the exposition out. We spoke to a lot of top-notch production companies, really amazing minds, and each had a territory to go out to, different studios they work with. Aggregate hit it out of the park, and we found a great creative partner.

"I'm excited because we’re shooting for an "Arrival"-level film. Obviously, "Contact" was an influence, but really this is much more along the lines of "Stalker," which is based on the book, "Roadside Picnic." Like movies that are smaller in scope but very deep and heartfelt. "Hole in the Sky" takes place in Oklahoma, and it's just as big of a character as anything in this film. It's literally going back to where I grew up, which is very fun."

"Hole in the Sky" will be published by Doubleday on Oct. 7, 2025.

From claims of aliens crashing on Earth and UFOs being hidden on military bases, to Mars being abnormally large and the moon turning green, space tends to attract some outlandish or at least highly unproven claims that should be vetted carefully.

Here are some of the biggest space myths and conspiracy theories that just won't go away.

1. The Apollo moon landings were fake

Twelve NASA astronauts walked on the moon between 1969 and 1972, but in the decades since Apollo 11 astronauts first set foot on the moon, many theories have been put forward claiming that the whole Apollo program was staged. However, the Lunar Reconnaissance Orbiter has since released photos of the landing sites as they appear on the lunar surface many years later.

Some of the questions moon landing deniers ask are "Why are there no stars in the sky in the moonwalkers' photos? Why are the U.S. flags fluttering on the surface? Why do you see footprints in the pictures, but no marks from the lunar modules that landed there?"

It turns out those questions are easy to answer than you may think.

There are no stars in the sky for the same reason you don't see stars during the day on Earth, according to NASA: The bright glow of daylight on the surface washes them out.

U.S. flags planted into the lunar soil had metal rods sewn in them to appear as though they were moving, according to NASA. Without these wires, the flag would have hung straight down, making for a pretty lackluster photo prop.

And the lunar modules, though heavier, didn't put prominent marks in the surface in some places because their mass was more evenly distributed than the astronauts' weight was in their boots.

2. NASA is a lie

Some people actually believe NASA's whole function is not to explore space, but to generate space-related hoaxes. (The Apollo moon landing is a famous example that we'll explore in the next slide.) People who believe this conspiracy, sometimes flagged with the hashtag "#NASAhoax" on social media, will say that amazing space pictures of Mars, Pluto and even Earth are fake, computer-generated imagery (CGI).

NASA was formed in 1958 "to provide for research into problems of flight within and outside the Earth's atmosphere, and for other purposes," according to the National Aeronautics and Space Act of 1958, which then-president Dwight D. Eisenhower signed into law shortly after the start of the space race against the Soviet Union.

Since then, NASA has launched hundreds of satellites into orbit around Earth, the moon and several other worlds. In fact, NASA spacecraft have orbited, flown by or landed on every planet in the solar system. NASA also sends astronauts into orbit, where they conduct research at the International Space Station (ISS).

If you're not convinced, you are free to travel to Florida's Space Coast to watch a rocket launch for yourself. It's also quite easy to see the space station and other satellites with your own eyes with the help of a satellite tracker.

3. The Earth is flat

This myth is so popular that there is even a group named after it: the Flat Earth Society. Members of the organization argue that the horizon is always at eye level, which they say would not be possible if the Earth were round. They also say there is no full movie of the Earth rotating from space — which is not true, as NASA has published multiple videos taken from satellites, including a live video of Earth from the ISS, which orbits our planet 16 times per day.

One way of demonstrating to yourself that the Earth is round is to consider how orbits of satellites work. Satellites constantly "fall" around the Earth as they are pulled around by our planet's gravity; they just need to be traveling fast enough at a high enough altitude to not slam into the atmosphere. Or, you can look at the amazing pictures taken by astronauts at the ISS.

4. Planet Nine will kill us

In April 2016, the New York Post tweeted, "A newly discovered planet could destroy Earth as soon as this month." The newspaper was referring to Planet Nine, a theoretical planet at the edge of the solar system. An accompanying video also claimed that the new planet would be throwing all sorts of asteroids and comets at Earth, which would supposedly end up pummeling our planet.

Although the existence of a ninth planet has not been confirmed, astronomers are actively looking for one to help explain motions of some objects in the icy Kuiper Belt, a vast region of icy objects beyond Neptune. If the planet is actually found, the planet will pose no threat to us, according to the California Institute of Technology's Mike Brown (who is one of the original backers of the Planet Nine theory).

5. Alien research is happening at Area 51

The 1996 movie "Independence Day" is one of the main sources of the Area 51 hoax, which claims that aliens and their technology — recovered from crashed flying saucers — are being studied secretly at a classified military base about 80 miles (130 kilometers) northwest of Las Vegas in the Nevada desert. Some people in the area around the base claim that they have seen strange lights or objects flying in or out of this area.

While the testing and development conducted at Area 51 is classified, the U.S. government has acknowledged its existence (although the CIA officially calls it "Homey Airport" or "Groom Lake").

A part of Edwards Air Force Base, the area was a known location for high-technology airplane flights in the 1960s and 1970s. It first served as a proving ground for Lockheed U-2 and A-12 OXCART spy planes as early as 1955. UFO sightings reported in the area were indeed unidentified objects, but only because the planes were top-secret — not because they were flown by aliens.

6. There is a killer planet known as "Nibiru"

Conspiracy theorists say another dangerous planet is Nibiru, which was first mentioned in the 1976 book "The Twelfth Planet," by Zecharia Sitchin. In the book, Sitchin translated ancient Sumerian cuneiform and claimed that the text is proof of a planet beyond Neptune called Nibiru that orbits the sun every 3,600 years.

Years later, self-proclaimed psychic Nancy Lieder claimed to have communicated with extraterrestrials who said Nibiru would collide with Earth in 2003. When that didn't happen, the date was moved to 2012 (and linked, of course, with the 2012 doomsday predictions). Of course, the collision never occurred, the world didn't end in 2012 and no astronomer has ever found a planet on a collision course with Earth.

7. There is a face on Mars

In 1976, NASA's Viking 1 spacecraft took a picture of what appeared to be a face on Mars. Immediately, some people said there must have been aliens on the Red Planet that left that face behind as evidence of their existence. NASA, however, pointed out that the suspected face is really just a pile of rocks casting shadows that resemble face-like features.

NASA followed up with better-resolution pictures taken from the Mars Reconnaissance Orbiter and the Mars Global Surveyor in 1998 and 2001, respectively. These new images made it quite clear that the "face on Mars" is nothing more than a trick of light and shadows on a completely normal Martian mound.

8. The moon Iapetus is an alien Death Star

Iapetus is a moon of Saturn that looks somewhat like the infamous Death Star in the "Star Wars" franchise, with a large crater that resembles the fictional weapon's superlaser focus lens. The Death Star is a planet-killing machine that destroys entire worlds with its outrageously powerful laser. It was prominently featured in the 2016 movie "Rogue One: A Star Wars Story," as well as in 1977's "Star Wars: Episode IV - A New Hope."

A Daily Mail article published in May 2016 claimed Iapetus is an artificial object crafted by aliens. As "evidence," the article cited a photo taken by NASA's Cassini spacecraft in 2004. In the photo, there's a line around the moon's equator that resembles the equatorial trench around the Death Star.

But this line isn't nearly as interesting as the Death Star's trench, which houses the battle station's engines, thrusters and docking bays. That line is nothing more than a mountain ridge, and Iapetus is actually just made up of boring old rock and ice. Cassini has flown by the moon to take pictures several times without being blasted by deadly alien lasers.

Saturn's moon Mimas, with it's giant crater Herschel, also looks surprisingly like the Death Star.

9. Saturn's hexagon is alien technology

Saturn's hexagon was first spotted when NASA's Voyager spacecraft flew by the giant, ringed planet in 1980. The bizarre, six-sided structure on the round planet's north pole caused quite the stir, because straight lines and polygons are not so common in nature.

Immediately after the Voyager returned its first images of Saturn's strange feature, even stranger theories arose to explain it, including that it was somehow related to alien technology, or perhaps even was a gateway to hell. The hexagon is not artificial, but rather a weird-looking hurricane at Saturn's pole.

NASA has done several flybys of this region with the Cassini spacecraft, studying the haze particles and other features of the storm, to try to learn more about its unusual properties.

10. Mars is as big as the moon

Originating in 2003, the infamous Mars hoax asserts that Mars was closer to Earth than it had been in the 60,000 years prior, and that the planet will appear as large as the full moon. What started out as a misconstrued email turned into a recurring rumor that gets reshared every August and, naturally, has spread to social media as it became more popular.

Although Mars is indeed relatively close to Earth in a cosmic sense, it will never be as large as the full moon. It will appear as a red dot in the sky, just as the ancient astronomers saw it. If you'd like to see Mars magnified, take out a telescope or look at one of NASA's spectacular Mars pictures.

11. The moon will turn green

In spring 2016, there was a rumor that the moon would turn green because several planets had aligned and caused an eerie glow, according to EarthSky. This was supposed to happen on April 20 and again on May 29 for the first time since 1596, the rumor alleged.

The moon never actually turned green, although it can appear red during a lunar eclipse, when the moon passes through Earth's shadow. In the same way sunsets often appear red, sunlight is scattered as it passes through Earth's atmosphere, casting a reddish shadow on the moon's surface.

Skywatching columnist Joe Rao debunked this green-moon myth. He pointed out that a full moon actually took place on April 22, 2016, and speculated that the April 20 date of the "green moon" might have to do with "National Weed Day," popularly known as 4/20. Considering that the last green moon supposedly happened 420 years ago as well, this doesn't appear to be a coincidence.

12. Earth will go dark for two weeks

In July 2015, a website called "NewsWatch33" wrote an article claiming that Earth would have 15 days of complete darkness that year. The website, which is actually a fake news site, was borrowing from an older version of the tale that has been circulating for years, according to debunking website Snopes.

As we all know, Earth did not actually experience that much darkness that year. (The article claimed that the alleged darkness was partly due to a Jupiter-Venus conjunction, which actually took place more than 500 million miles apart.) Darkness occurs when the Earth rotates, causing the sun to "set" on the local horizon. Brief periods of darkness can also happen when the sun is totally obscured during total solar eclipses, which occur rarely in any particular spot on Earth. But even during an eclipse, Earth is never completely in the dark.

13. Zero-gravity day will make you weightless

If you ever wanted to leap into the sky and soar like Superman, this hoax is for you. In late 2014 and early 2015, a widely shared story claimed that on Jan. 4, 2015, everyone on Earth would experience weightlessness due to a rare alignment of the planets. A doctored image of a purported tweet from NASA's Twitter account that went around on social media fooled a lot of people into believing the hoax.

But, of course, nobody floated off the surface of Earth that day. Earth's gravity is too strong for people to become weightless. The only way to experience weightlessness without going to space is to ride aboard a plane that performs parabolas, with some including a few seconds of weightlessness. This is sometimes nicknamed the Vomit Comet.

14. Alien spacecraft caused a mysterious explosion

Back in 2004, an expedition of Russian researchers working in Siberia claimed to have discovered "an extraterrestrial device" close to where the mysterious Tunguska explosion occurred. Scientists still aren't sure exactly what it was that blew up in the sky over Siberia that day in 1908, but the leading theory is that it was a large meteorite or an asteroid, according to Live Science.

The Tunguska incident flattened hundreds of square miles of forest, and signs of the destruction were visible even decades afterward. At the time, news reports claimed that evidence of aliens was found at the site, but this claim was never substantiated. "The Russian team stupidly stated long before they went to Siberia that the main intention of their expedition was to find the remnants of an alien spaceship," Benny Peiser, a researcher at Liverpool John Moores University in the U.K., told Space.com. "And bingo! A week later, that's what they claim to have found."

15. UFO was caught "refueling" at the sun

NASA has a fleet of sun-gazing spacecraft that keep an eye on space weather, especially during solar eruptions. In 2012, telescopic images appeared to show something in the shadows. On YouTube, some viewers said this could be a UFO that was refueling by using the solar plasma.

However, NASA pointed out that the feature is actually something called a "prominence," which has cooler and denser plasma than the outer atmosphere of the sun, or the corona. Scientists are still trying to figure out how solar prominences develop, but they're pretty sure it has nothing to do with aliens.

16. There is a ______ on Mars!

With NASA's Opportunity and Curiosity rovers regularly taking pictures of the Martian surface, viewers have the chance to check out what they're doing in almost real time. NASA puts the raw images online for the public to see. But over the years, some weird shapes have cropped up. In 2008, for example, the Opportunity rover appeared to photograph a female figure. Other photos have shown things shaped like animals, spoons or other items.

You can imagine that, with all of the rocks available on Mars, some of them would happen to look like familiar objects. In fact, the human brain tends to perceive meaningful images in random patterns — a phenomenon known as pareidolia.

When evaluating the claims, consider that the Martian environment is extremely harsh to life as we know it; the surface is baked with radiation, the "air" is mostly carbon dioxide and there's not much atmospheric pressure.

17. I just saw a bright UFO!

It's a familiar trope for police stations and astronomy writers. From time to time, somebody will call (or write) in to say they just saw a UFO in the sky. While UFO is the term used for any flying object that an observer cannot identify, many people claim that they are alien spaceships. They spotted a bright light around sunset, or saw a light moving around in an unfamiliar way.

While every situation is different, one common explanation for "UFOs" is actually another extraterrestrial object: Venus. Venus can be extremely bright when it's at its closest, because it's relatively near Earth. The planet is also extremely reflective because the sun's light bounces off the clouds. So before calling to say you've spotted a UFO, check your sky charts!

18. NASA can travel faster than light

If you've seen the "Star Trek" clips that show the Enterprise spaceship warping into another sector, you might have wondered how fast NASA is making progress on being able to move at the speed of light. The EmDrive has created years of speculation, with some breathlessly saying NASA must be on the verge of breaking the famed barrier.

In reality, NASA is downplaying the reports. The engine in question is a prototype that is producing some interesting results, such as appearing to create thrust when there was no reason for this to happen – and thereby violating Newton's Third Law of Motion. That said, NASA has not yet verified the results from these tests, and the engine has not been widely discussed in peer-reviewed research.

19. We've launched balloons into space!

With the advent of high-resolution, miniature cameras, several people have decided to strap these cameras on to high-altitude balloons and take pictures from up high. They've caught glimpses of blackness and, at times, taken interesting tiny passengers along (such as 1000 Lego minifigures). So they must be in space, right?

There's no way a helium balloon can get into space, according to the California Institute of Technology, and simple physics explains why. When a balloon rises into the sky, the air inside will expand in response to the dropping atmospheric pressure and eventually pop. Even Felix Baumgartner's stunning high-altitude balloon jump in 2012 was not actually from space, but from the stratosphere, which extends to roughly 31 miles (50 kilometers) above the Earth's surface.

At that altitude the air is thin enough to see the blackness of space, but thick enough to support special high-altitude balloons. The boundary between Earth's atmosphere and outer space is about twice as high as the upper limits of the stratosphere.

20. There are canals on Mars

Author Percival Lowell became one of space's first popularizers when he wrote many books for the general public back in the late 1800s and early 1900s. In these books and other writings, he said there were canals on Mars built by an intelligent civilization, perhaps to move water into desert-stricken areas. He claimed to have seen the canals in his own telescope, and produced several sketches that are still available on the internet today.

There are no artificial canals on Mars. Several spacecraft have flown by the planet or orbited it, and not one has caught signs of aliens from orbit. What they have seen, however, are smaller channels that were created by nature – likely from water, ice or other processes that cause erosion.

21. A star is flinging comets at Earth

A long-standing theory known as Nemesis supposes that there is some sort of "death star" on the outer edge of the solar system, whose orbital motions perturb comets in an icy region of objects known as the Oort Cloud. According to the myth, the star's gravity throws these comets toward the inner solar system, and these comets collide with Earth and cause mass extinctions once every 27 million years.

However, a 2011 study concluded that this idea is unlikely, because the comet strikes in recorded history haven't happened with any regularity. The pattern that was recorded in the hoax is actually a statistical artifact, or the result of researchers trying to find patterns in nature where they do not exist, the study's authors found.

22. There's life on Venus

Back in the 1970s and 1980s, the Soviet Union sent several uncrewed missions to study Venus. Ten of these Venera probes landed on the surface of Venus and were able to transmit data and images for a few minutes before succumbing to the planet's extreme atmosphere. In 2012, the Russian news service RIA Novosti reported that Leonid Ksanfomaliti, a scientist who worked on the Venera missions, suggested that the photographs showed living objects moving around on the planet's surface. (RIA Novosti ceased operations in 2013.)

These alleged life-forms on Venus are just an example of "letting your mind see patterns in low-resolution data that simply aren't real," Jonathon Hill, a research technician who processes images taken during NASA's Mars missions, explained to Space.com's sister site, LiveScience, in 2012.

According to NASA, the objects that appeared to be moving were actually camera-lens covers that automatically popped off of the cameras after landing LiveScience reports. These half-circle objects were seen in images from Venera-13 and Venera-14, two identical spacecraft that landed about 590 miles (950 km) apart. Both had two identical cameras — one in the front and one in the back — so it makes sense that the covers would appear in different places. Another photograph that Ksanfomaliti said was a scorpion is actually a blur in the image.

23. An asteroid is about to crash into Earth

This recurring rumor claims that a threatening "doomsday" asteroid is about to slam into our planet. An example from 2015 had an asteroid purported to hit Earth in late September, when it would supposedly wreak devastation from its impact point near Puerto Rico. NASA quickly dismissed the reports — which turned out, as usual, to be false. But that's not to say that asteroids will never hit our planet.

NASA and a network of monitoring telescopes across the world are cataloging all known asteroids wider than 459 feet (140 meters) across in line with a 2005 congressional mandate. (Smaller asteroids, if found, are also cataloged.) Of the space rocks discovered so far, NASA has not found a single asteroid that has a high probability of hitting Earth in the foreseeable future.

24. Aliens landed in Roswell, New Mexico

On a ranch in Roswell, New Mexico, so the story goes, an alien spacecraft crashed in 1947. While the accounts of exactly what happen vary, the legend claims that a disc or some sort of spacecraft was found on a ranch, and that the government quickly covered up the evidence.

While rumors of aliens circulated, some people speculated that the crash was just a plain old weather balloon that might not have been recognized by the local community. The U.S. military acknowledged the "spacecraft" was actually a weather balloon sent aloft as part of Project Mogul, which involved flying microphones on high-altitude balloons to listen for sound waves generated by possible Soviet Union nuclear tests.

25. Climate change isn't real

Earth is on an abnormal warming trend. Arctic ice is melting, the sea level is rising and temperatures are going to extremes in many locations around the world. Why is this happening? Anti-climate-change conspirators have many explanations: solar activity, radiation, the Earth's (and sun's) movements around the Milky Way, among other theories.

While there are many components of climate change, the fact that humans have contributed to it is indisputable, according to NASA. Temperature graphs show that the climate has not warmed this much, this quickly in all of Earth's history (as seen in geological records), and that the increase correlates with increased industrialization.

Additional resources

For more myths about space, you can read this article by How It Works magazine. Additionally, you can watch this video by BBC Earth Lab.

Bibliography

"National Aeronautics and Space Act of 1958 (Unamended)". National Aeronautics and Space Administration. https://history.nasa.gov/spaceact.html

"Modern myths of Mars". Proc. SPIE 6309, Instruments, Methods, and Missions for Astrobiology IX, 63090C (14 September 2006). https://doi.org/10.1117/12.676304

Long-lived civilizations may have many motivations for wanting to move somewhere else in the galaxy. They may need to escape an impending supernova, for example. Maybe they need to scout our new natural resources. Or maybe they just feel like exploring.

Given the enormous distances between the stars, however, interstellar travel is tremendously difficult and time-consuming. So, instead of leaving their system, an intrepid alien species might decide to take their system with them. The main advantage of accelerating their own star would be that they get to keep it with them as they travel. They would do this by causing their star to either radiate or evaporate in just one direction, which would propel the star, along with all of its planets, to a new location in the galaxy.

Astronomers have investigated whether "hypervelocity" stars (which, as their name suggests, are stars with an extraordinarily high velocity) may have been purposefully launched by alien civilizations, but the known candidates show no signs of artificial interference.

Related: Astronomers Detect a Swarm of Tiny Objects Orbiting an Alien Sun

In a recent paper, Clement Vidal, a philosopher at the Vrije University Brussels in Belgium, pointed out that most stars are not solitary but rather belong to binary systems. This means we might be missing half of the potential artificially accelerated stars. Even better, binary systems offer many advantages over their solo counterparts, Vidal wrote in his paper, which has not been peer-reviewed or published in a scientific journal.

Vidal took a model system consisting of a neutron star with a low-mass star tightly orbiting it. This setup provides the most flexibility in steerability and thrust.

The alien civilization would have to figure out a way to eject material from the star. This could be from asymmetric magnetic fields or from some device that causes uneven heating on the stellar surface. No matter what, the goal would be to get the star to eject more material in one direction than another. This would create thrust, pushing the binary system in the opposite direction, Vidal explained.

If the civilization were to place the machinery on or near the neutron star, where the strong gravity could provide a ready source of energy, they could steer the binary system by carefully cycling the machine off and on. For example, if they activated the machine only at the exact same point in the orbit, they would send the binary system in one direction. If they left the machine activated slightly longer, they would adjust their course, pointing their movement in any direction they wished along the orbital plane.

They could even steer their system in new off-orbit directions by altering the direction in which their machine was pointed, effectively changing the orbit of the neutron star around its companion.

Amazingly, there are real systems in the universe that match these kinds of characteristics, like the "black widow" pulsar PSR J0610-2100 and the "redback" pulsar PSR J2043+1711. Both of those systems have significant accelerations. Although they are unlikely to be caused by alien engineering, they are worth looking into, Vidal concludes. At least, while they're still around.

Mike Sori is an Assistant Professor of Planetary Science at Purdue University.

On Oct. 14, 2024, NASA launched a robotic spacecraft named Europa Clipper to Jupiter’s moons. Clipper will reach the ice-covered Jovian moon Europa in 2030 and spend several years collecting and sending valuable data on the moon’s potential habitability back to Earth.

Clipper isn’t the only mission highlighting researchers’ interest in Jupiter and its moons.

On April 13, 2023, the European Space Agency launched a rocket carrying a spacecraft destined for Jupiter. The Jupiter Icy Moons Explorer – or JUICE – will spend at least three years on Jupiter’s moons after it arrives in 2031.

I’m a planetary scientist who studies the structure and evolution of solid planets and moons in the solar system.

There are many reasons my colleagues and I are looking forward to getting the data that Europa Clipper and JUICE will hopefully be sending back to Earth in the 2030s. But perhaps the most exciting information will have to do with water. Three of Jupiter’s moons – Europa, Ganymede and Callisto – are home to large, underground oceans of liquid water that could support life.

Related: SpaceX Falcon Heavy rocket launches NASA's Europa Clipper probe to explore icy Jupiter ocean moon (video)

Meet Io, Europa, Ganymede and Callisto

Jupiter has dozens of moons. Four of them in particular are of interest to planetary scientists.

Io, Europa, Ganymede and Callisto are, like Earth’s Moon, relatively large, spherical complex worlds. Two previous NASA missions have sent spacecraft to orbit the Jupiter system and collected data on these moons. The Galileo mission orbited Jupiter from 1995 to 2003 and led to geological discoveries on all four large moons. The Juno mission is still orbiting Jupiter today and has provided scientists with an unprecedented view into Jupiter’s composition, structure and space environment.

These missions and other observations revealed that Io, the closest of the four to its host planet, is abuzz with geological activity, including lava lakes, volcanic eruptions and tectonically formed mountains. But it is not home to large amounts of water.

Europa, Ganymede and Callisto, in contrast, have icy landscapes. Europa’s surface is a frozen wonderland with a young but complex history, possibly including icy analogs of plate tectonics and volcanoes. Ganymede, the largest moon in the entire solar system, is bigger than Mercury and has its own magnetic field generated internally from a liquid metal core. Callisto appears somewhat inert compared to the others, but serves as a valuable time capsule of an ancient past that is no longer accessible on the youthful surfaces of Europa and Io.

Most exciting of all: Europa, Ganymede and Callisto all almost certainly possess underground oceans of liquid water.

Ocean worlds

Europa, Ganymede and Callisto have chilly surfaces that are hundreds of degrees below zero. At these temperatures, ice behaves like solid rock.

But just like Earth, the deeper underground you go on these moons, the hotter it gets. Go down far enough and you eventually reach the temperature where ice melts into water. Exactly how far down this transition occurs on each of the moons is a subject of debate that scientists hope to resolve with JUICE and Europa Clipper. While the exact depths are still uncertain, scientists are confident that these oceans exist.

The best evidence of these oceans comes from Jupiter’s magnetic field. Saltwater is electrically conductive. So as these moons travel through Jupiter’s magnetic field, they generate a secondary, smaller magnetic field that signals to researchers the presence of an underground ocean. Using this technique, planetary scientists have been able to show that the three moons contain underground oceans. And these oceans are not small – Europa’s ocean alone might have more than double the water of all of Earth’s oceans combined.

An obvious and tantalizing next question is whether these oceans can support extraterrestrial life. Liquid water is an important piece of what makes for a habitable world, but far from the only requirement for life. Life also needs energy and certain chemical compounds in addition to water to flourish. Because these oceans are hidden beneath miles of solid ice, sunlight and photosynthesis are out. But it’s possible other sources could provide the needed ingredients.

On Europa, for example, the liquid water ocean overlays a rocky interior. That rocky seafloor could provide energy and chemicals through underwater volcanoes that could make Europa’s ocean habitable. But it is also possible that Europa’s ocean is a sterile, inhospitable place – scientists need more data to answer these questions.

Upcoming missions from ESA and NASA 

Europa Clipper and JUICE are set up to give scientists game-changing information about the potential habitability of Jupiter’s moons. While both missions will gather data on multiple moons, JUICE will spend time orbiting and focusing on Ganymede, and Europa Clipper will make dozens of close flybys of Europa.

Both of the spacecraft will carry a suite of scientific instruments built specifically to investigate the oceans. Onboard radar will allow Europa Clipper and JUICE to probe into the moons’ outer layers of solid ice. Radar could reveal any small pockets of liquid water in the ice, or, in the case of Europa, which has a thinner outer ice layer than Ganymede and Callisto, hopefully detect the larger ocean.

Magnetometers will also be on both missions. These tools will give scientists the opportunity to study the secondary magnetic fields produced by the interaction of conductive oceans with Jupiter’s field in great detail and will hopefully give researchers clues to salinity and volumes of the oceans.

Scientists will also observe small variations in the moons’ gravitational pulls by tracking subtle movements in both spacecrafts’ orbits, which could help determine if Europa’s seafloor has volcanoes that provide the needed energy and chemistry for the ocean to support life.

Finally, both craft will carry a host of cameras and light sensors that will provide unprecedented images of the geology and composition of the moons’ icy surfaces.

Maybe one day, a spacecraft will be able to drill through the miles of solid ice on Europa, Ganymede or Callisto and explore oceans directly. Until then, observations from spacecraft like Europa Clipper and JUICE are scientists’ best bet for learning about these ocean worlds.

When Galileo discovered these moons in 1609, they were the first objects known to directly orbit another planet. Their discovery was the final nail in the coffin of the theory that Earth – and humanity – resides at the center of the universe. Maybe these worlds have another humbling surprise in store.

This notion, along with the discovery that habitable worlds are common throughout the cosmos, has influenced a question that has perplexed scientists and others for decades: "Why is the universe so quiet?" This conundrum, which is said to have been proposed by physicist Enrico Fermi in 1950, is known as the Fermi paradox. If our solar system is young compared with the rest of the universe and humans could be capable of interstellar travel someday, shouldn't we have seen signs that other intelligent entities have spread throughout the cosmos by now? Basically, where are the aliens?

Perhaps we haven't encountered alien civilizations because there's a "universal limit to technological development" (ULTD) for every intelligent species in the universe and this limit sits well below a civilization's ability to colonize an entire galaxy, Antonio Gelis-Filho, a researcher in public policy at the Getúlio Vargas Foundation at the School of Business Administration (FGV EAESP) in Brazil, proposed in a recent paper published in the journal Futures. 

"If the ULTD hypothesis is correct, there has never been, there is not and there will never be something like an interstellar civilization, or anything similar to an 'interstellar conversation,'" Gelis-Filho told Space.com in an email. 

Related: Are we alone? Intelligent aliens may be rare, new study suggests

Based on the history of the rise and fall of human civilizations, the feasibility of constructing and running scientific projects that expand our knowledge and technology, and the apparent lack of technological intelligence elsewhere in the cosmos, Gelis-Filho thinks we should be careful about assuming the technological capacities of humans and other intelligent beings are limitless. 

The "uncrossable gap" 

Nobel prize-winning physicist Richard Feynman once said, "What I cannot create, I do not understand." The most straightforward interpretation of this is that our technology — what we can create — is constrained by our knowledge. 

There are, of course, natural limits to human technology. We can't travel in a straight line faster than the speed of light, for example. There may also be natural barriers to human knowledge — facts about the universe that are forever inaccessible to us due to the configuration of our biology. Sure, we have created technology that scaffolds our senses and cognition: Microscopes let us peer into the world of the small, telescopes provide a window into the world of the big, and computers crunch numbers and data that our individual minds are incapable of processing. 

However, the technologies and experiments that allow us to expand our knowledge are coming at an ever-increasing price. Projects like the Large Hadron Collider at CERN ($4.75 billion to construct and $286 million annually), the International Space Station ($3 billion per year), and the international effort to achieve nuclear fusion at ITER (an estimated $18 billion to $20 billion for construction) show that human efforts to probe our scientific horizons require increasing energy and resources. 

"If we are candid about it, the fact is that the last major fundamental advances in the science of the universe (macro- and micro-realms, cosmology and quantum mechanics) are almost a hundred years old," Gelis-Filho said. 

Sure, black holes and other phenomena are much better understood today than they were a century ago, but their theory is nowhere as consequential to human technology as relativity and quantum mechanics have been, Gelis-Filho contends.

Just "compare the scientific evolution from 1830 (no theory of evolution, no theory of electromagnetism) to 1930 (relativity and quantum mechanics already there) and from 1930 to 2024 (still no unifying theory) for us to perceive that the rate of advancement is slowing, to say the least," Gelis-Filho said. "Low-hanging fruits have already been picked. The remaining ones seem to be hanging from impossibly high branches." 

The growing price of probing the frontiers of human knowledge means we might decide the price is too high. Indeed, the European commission recently abandoned its plan to select a number of billion-euro flagship research projects, which included plans to convert solar and wind energy into fuels, and to bring cell and gene therapies into clinical settings. In such a case, the development of new technologies that leverage new breakthroughs in our understanding of reality will also come to a standstill, along with our dreams of becoming an interstellar civilization. 

Any intelligent civilization in the cosmos will have to face this same scenario, Gelis-Filho said. At a certain point, no matter how ingenious they become, they will have to make a decision: Do we build a particle accelerator as large as the Milky Way to test our new unifying theory, for example, or do we build necessary infrastructure for our civilization's survival? 

The ULTD hypothesis sustains that, even if a civilization decided to build such a machine to test the limits of their knowledge, they would discover that the levels of energy needed to perform experiments to facilitate a leap in scientific knowledge do not increase linearly. They would reach a point where their current technology would not allow them to cross the gap between one level and the next. 

"Since the laws of physics are the same throughout the universe, every single civilization will eventually clash against that 'uncrossable gap,'" Giles-Filho said. 

The cost of increasing societal complexity  

Gelis-Filho also thinks lessons from the rise and fall of human civilizations can be applied to this astrobiological context. Complex societies expand by adding layers of societal complexity to produce more "energy" to keep growing. However, after a certain point, complexity does not "pay for itself," and its returns will decrease, he said. 

"If we think of a hunter-gathering society, the number of social roles (chief, hunter, collector and so on) is minimal; in the Late Roman Empire, it was much higher and in our industrial society it is immensely higher," Gelis-Filho explained.

Of course, with added specialization, more complex societies can produce more. As people developed agriculture on Earth, for instance, the influx of food provided by the new technology led to new societal roles aimed at increasing production further. But as the level of complexity increased, so did the need for costly infrastructure to support it.  

Related: First contact with aliens could end in colonization and genocide if we don't learn from history

Gelis-Filho borrows his argument from Joseph Tainter, an archaeologist who studied many complex societies throughout history. Tainter  hypothesizes that, although the fatal blow to a society may vary (e.g., war, drought, epidemics or an astronomical event), the root cause is always the same: decreasing returns on complexity that have made the society fragile. 

"I have applied the concept to any technological society anywhere in the universe," Gelis-Filho said. "Advanced spatial technology demands legacy infrastructure to be developed. That infrastructure is just a part of societal complexity. … It is possible that many non-terrestrial societies have collapsed because of diminishing returns on societal complexity, even before clashing against the limits imposed by energy requirements to test scientific theories."

Cosmic messages in a bottle 

Despite all of this, Gelis-Filho doesn't rule out the possibility of receiving a message or signal from another intelligent civilization. The universal limit to technological development prohibits technological development beyond a level that prevents the organized, self-sustaining spread of a civilization beyond its solar system. 

"However, it does not preclude the existence of 'castaway technology,' like wandering dead space probes (just think about the Voyager 1 in a hundred thousand years, silently crossing our galaxy), isolated messages being received (the Wow! signal being a candidate) or even 'alien dead Voyagers' being retrieved by us (however improbable that event is)," he said. 

Such attempts to communicate with other intelligent civilizations across the vastness of space resemble "great cosmic bottle messages" — like a stranded captain of a sunken ship on a remote island trying to signal to the outside world with the rudimentary tools they have, Gelis-Filho explained. 

Giles-Filho's hypothesis is one possible explanation for why our attempts to observe an interstellar civilization have fallen short. Yes, we have been searching for signs that we are not alone in the cosmos for only a few decades. Maybe we haven't been looking long enough, in the right place or even for the right thing. The unambiguous detection of an intelligent alien civilization would obviously prove the ULTD hypothesis wrong, as would the sudden leap in knowledge that could facilitate the expansion of human civilization into the stars. Until then, the ULTD hypothesis provides a sobering reminder that our species' destiny is not a given.

The film racked up a global box office total of $347 million and appeased "Alien" acolytes around the planet with its return to old-school scares and its nods to the first two installments in the series, 1979's "Alien" and 1986's "Aliens."

Now that its theatrical run has subsided, 20th Century Studios' "Alien: Romulus" will invade digital retailers (Prime Video, Apple TV and Fandango at Home) on Oct. 15. It will then sneak into your homes on 4K Ultra HD, Blu-ray and DVD on Dec. 3, complete with bonus featurettes, alternate and extended scenes, interviews with Fede Alvarez and Ridley Scott, VFX secrets, promo materials, behind-the-scenes content and much more.

Here's the full description of the impactful fright-fest:

"This truly terrifying sci-fi horror-thriller takes the phenomenally successful 'Alien' franchise back to its iconic roots. While scavenging the deep ends of a derelict space station, a group of young colonizers come face-to-face with the most relentless and deadly life form in the universe. Starring Cailee Spaeny, David Jonsson, Archie Renaux, Isabela Merced, Spike Fearn and Aileen Wu, 'Alien: Romulus' is directed by horror master Fede Alvarez from a screenplay by Alvarez and frequent collaborator Rodo Sayagues based on characters created by Dan O'Bannon and Ronald Shusett. Ridley Scott — who directed the original 'Alien' and the series entries 'Prometheus' and 'Alien: Covenant' — produces with Michael Pruss and Walter Hill."

Related: 'Alien: Romulus' is a visceral return to form for a venerable sci-fi franchise (review)

The 4K UHD presentation will also be available for purchase in a collectible limited edition SteelBook decorated with custom artwork and box packaging. 

Additionally, Xenomorph fans can honor director Ridley Scott's original 1979 sci-fi classic, "Alien," which celebrates its 45th anniversary this year, by grabbing a special Two-Movie Collection digital bundle pairing "Alien" and "Alien: Romulus" on Oct. 15.

Check out the total rundown of home video bonus features:

• "Return to Horror: Crafting 'Alien: Romulus'"
• "The Director’s Vision" – Discover how one of today’s greatest horror directors, Fede Alvarez, collaborated with master filmmaker Ridley Scott to craft a new, heart-pounding chapter in the "Alien" franchise.
• "Creating the Story" – Learn what inspired the story of "Alien: Romulus" and see the many easter eggs from previous Alien installments that you may have missed.
• "Casting the Faces" – Meet the stars of "Alien: Romulus" as they take us inside the hearts and minds of their characters. Explore the parallels between Rain and the iconic franchise heroine, Ripley, and learn how filmmakers brought back a face from the past.
• "Constructing the World" – Explore the massive, practical sets of "Alien: Romulus" that hearken back to the futuristic style established in the '80s and get up close and personal with a hoard of practically built facehuggers, chestbursters, and xenomorphs.
• "Inside the Xenomorph Showdown" – Experience the film's climactic zero-gravity sequence from every angle as filmmakers break down what it took to make the moment spectacular. From sets and performances, to wirework, stunts, and VFX, see how it all came together.
• "'Alien:' A Conversation" – A special conversation with Ridley Scott and Fede Alvarez for the "Alien" 45th Anniversary theatrical re-release.

Tony Milligan is a Research Fellow in the Philosophy of Ethics at King's College London.

The idea that aliens may have visited the Earth is becoming increasingly popular. Around a fifth of UK citizens believe Earth has been visited by extraterrestrials, and an estimated 7% believe that they have seen a UFO.

The figures are even higher in the US – and rising. The number of people who believe UFO sightings offer likely proof of alien life increased from 20% in 1996 to 34% in 2022. Some 24% of Americans say they’ve seen a UFO.

This belief is slightly paradoxical as we have zero evidence that aliens even exist. What's more, given the vast distances between star systems, it seems odd we'd only learn about them from a visit. Evidence for aliens is more likely to come from signals from faraway planets.

In a paper accepted for publication in the Proceedings of the International Astronomical Union, I argue that the belief in alien visitors is no longer a quirk, but a widespread societal problem.

The belief is now rising to the extent that politicians, at least in the U.S., feel they have to respond. The disclosure of information about claimed Unidentified Anomalous Phenomena (UAPs rather than UFOs) from the Pentagon has got a lot of bi-partisan attention in the country.

Much of it plays upon familiar anti-elite tropes that both parties have been ready to use, such as the idea that the military and a secretive cabal of private commercial interests are keeping the deep truth about alien visitation hidden. That truth is believed to involve sightings, abductions and reverse-engineered alien technology.

Belief in a cover-up is even higher than belief in alien visitation. In 2019, a Gallop poll found that a staggering 68% of Americans believed that "the U.S. government knows more about UFOs than it is telling."

This political trend has been decades in the making. Jimmy Carter promised document disclosure during his presidential campaign in 1976, several years after his own reported UFO sighting. Like so many other sightings, the simplest explanation is that he saw Venus. (That happens a lot.)

Hillary Clinton also suggested she wanted to "open [Pentagon] files as much as I can" during her presidential campaign against Donald Trump. As seen in the video below, Trump suggested he'd need to "think about" whether it was possible to declassify the so-called Roswell documentation (relating to the notorious claimed crash of a UFO and the recovery of alien bodies).

Former president Bill Clinton claimed to have sent his chief of staff, John Podesta, down to Area 51, a highly classified US Air Force facility, just in case any of the rumors about alien technology at the site were true. It is worth nothing that Podesta is a long-time enthusiast for all things to do with UFOs.

The most prominent current advocate of document disclosure is the Democratic Senate leader Chuck Schumer. His stripped back 2023 UAP disclosure bill for revealing some UAP records was co-sponsored by three Republican senators.

Pentagon disclosure finally began during the early stages of Joe Biden’s term of office, but so far there has been nothing to see. Nothing looks like an encounter. Nothing looks close.

Still, the background noise does not go away.

Problems for society

All this is ultimately encouraging conspiracy theories, which could undermine trust in democratic institutions. There have been humorous calls to storm Area 51. And after the storming of the Capitol in 2021, this now looks like an increasingly dangerous possibility.

Too much background noise about UFOs and UAPs can also get in the way of legitimate science communication about the possibility of finding microbial extraterrestrial life. Astrobiology, the science dealing with such matters, has a far less effective publicity machine than UFOlogy.

History, a YouTube channel part owned by Disney, regularly delivers shows about "ancient aliens." The show is now in its 20th season and the channel has 13.8 million subscribers. The NASA astrobiology channel has a hard won 20,000 subscribers. Actual science finds itself badly outnumbered by entertainment repackaged as factual.

Alien visitation narratives have also repeatedly tried to hijack and overwrite the history and mythology of indigenous people.

The first steps in this direction go back to Alexander Kazantsev's science fiction tale Explosion: The Story of a Hypothesis (1946). It presents the 1908 Tunguska meteorite impact event as a Nagasaki-like explosion of an alien spacecraft engine. In Kazantsev’s tale, a single giant black female survivor has been left stranded, equipped with special healing powers. This lead to her adoption as a shaman by the indigenous Evenki people.

NASA and the space science community do support efforts such as the Native Skywatchers initiative set up by the indigenous Ojibwe and Lakota communities to ensure the survival of storytelling about the stars. There is a real and extensive network of indigenous scholarship about these matters.

But UFOlogists promise a far higher profile for indigenous history in return for the mashing together of genuine indigenous stories about life arriving from the skies with fictional tales about UFOs, repackaged as suppressed history.

The modern alien visitation narrative has not, after all, emerged out of indigenous communities. Quite the opposite. It emerged in part as a way for conspiracy-minded thinkers in a Europe torn apart by racism to “explain” how complex urban civilizations in places like South America could have existed prior to European settlement.

Squeezed through a new age filter of 1960s counterculture, the narrative was flipped to value indigenous people as having once possessed advanced technology. Once upon a time, according to this view, every indigenous civilization was Wakanda, a fictional country appearing in American comic books published by Marvel Comics.

If all of this stayed in its own box, as entertaining fiction, then matters would be fine. But it doesn't, and they aren't. Visitation narratives tend to overwrite indigenous storytelling about sky and ground.

This is a problem for everyone, not just indigenous peoples struggling to continue authentic traditions. It threatens our grasp of the past. When it comes to insight into our remote ancestors, the remnants of prehistoric storytelling are few and precious, such as within indigenous storytelling about the stars.

Take the tales of the Pleiades, which date back in standard forms to at least 50,000 years ago.

This may be why these tales in particular are heavily targeted by alien visitation enthusiasts, some of whom even claim to be "Pleiadeans." No surprises, Pleiadeans do not look like the Lakota or Ojibwe, but are strikingly blond, blue-eyed and Nordic.

It is increasingly clear that belief in alien visitation is no longer just a fun speculation, but something that has real and damaging consequences.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

The views expressed are those of the author and do not necessarily reflect the views of the publisher.

The Alien movie franchise will soon expand with an Alien TV series too, which could keep the tradition of each creative team bringing their own sensibility to the universe alive. First, however, we've yet to see how Romulus strikes a balance between the first two classics while hopefully closing some of the gaps in the canon opened by Scott's Prometheus and Alien: Covenant, two divisive but fascinating prequels full of big ideas and bold swings.

Whether you're a newcomer to the Alien franchise or someone looking to get a full refresh before returning to theaters this summer, we recommend looking at our Alien movies in order and Alien movies ranked lists. There's also out best Alien games of all time list too, if you want to get in on the scares.

Egg

Of course, we can't start this exploration of the Xenomorph life cycle without the species' most basic form: the leathery (and rather large) eggs that were first seen in that memorable scene of the 1979 original. Characterized by their remarkable size and the 'goo' that covers them, as well as their four-lobed opening at the top, the alien eggs can seemingly lie dormant and wait for potential hosts (human, Engineer, or otherwise) for decades and maybe, given the Xenos' resilience and adaptiveness, even centuries.

Since the planned third entry of Scott's prequel trilogy never came to fruition and Romulus is taking the story to the period between Alien and Aliens, we don't really know the exact origin of the Engineer ship and the eggs inside it that the crew of the Nostromo found on LV-426 in the year 2122. 

We do know that Queens typically produce the eggs, but the original movie's novelization included the concept of 'eggmorphing' as the ultimate fate of Dallas and Brett, who'd been captured and cocooned by the Xenomorph roaming the Nostromo. The scene was reinstated partially in the movie's Director's Cut, and the eggmorphing process popped up again in other secondary Alien works, which is why many fans consider it a canonical ability of the species to reproduce and start the creation of a hive in the absence of a Queen.

Facehugger

Almost as iconic as the Xenomorph's main life stage is its facehugger form, which has become a mainstay of the movie series. Any living being that is caught by one of these is done for, as no non-lethal way to extract Xeno embryos and the ensuing chestbursters has been shown in the movies. 

The crab and spider-like facehuggers, whose fast movement and jumps are unsettling enough on their own, attach to a victim's face and release a strong paralytic chemical before latching on to their head with the legs. After the Xeno embryo is in place and can sustain itself inside the host, the facehugger detaches and dies. Any attempt to remove facehuggers is almost guaranteed to be fatal, as the parasite responds by tightening its grip on the victim and its acidic blood is as strong as that of an adult Xenomorph.

This stage of the life cycle is only skipped by the large Predalien, which was birthed from an impregnated Predator and first seen in Aliens vs. Predator: Requiem. That creature could directly produce and inject Xeno embryos into its victims, acting as the resulting hive's Queen.

Chestburster

The chestbursters represent the most unpredictable and fascinating stage of the aliens' life cycle, as what happens during this part of the evolution process defines the traits that shape the resulting Xenomorph. It seems that chestbursters are actually grown from the biological material of the hosts, which would explain why the resulting Xenos retain physical traits and even abilities from the living beings that unwittingly birth them later.

Typically, a chestburster violently erupts from the chest of its host, hence the nasty and disturbing nickname. It's at this stage when the Xenomorphs are most vulnerable, yet chestbursters are fast and silent once they escape their hosts' bodies. Once a secure location to cocoon and grow has been found, it'll become an adult Xenomorph in just a few hours.

Drone

The terrifying Xenomorph drone is the iconic alien in its most basic, recurrent, and memorable form — an almost perfect organism that's as lethal as it is industrious. Its main objective is to either grow or establish a hive, and will seek new hosts for gathering and impregnation, yet it can also kill any immediate threat to its integrity or the hive. Hosts other than humans produce different types of drones, such as the 'runner' birthed from a quadrupedal mammal on Fiorina 161 (Alien 3).

Drones are stronger and faster than a human, and are also extremely good climbers and jumpers. Moreover, like other adult Xenos, they appear to be able to survive even in the void of outer space. Its weapons are a piston-like tongue that is tipped with a second set of jaws, large claws, and the lance-like tip of its long tail. Even in death, they're savage, as any open wound will eject highly pressurized acid blood.

Warriors (and other adult Xenomorphs)

Once a hive is big enough, many drones will evolve into warriors, similar but more resilient Xenomorphs, often characterized by their 'ridged' heads. There are other subtypes which are tasked with more specific activities within and outside the hive. 

Much like drones, warriors and other subtypes retain the major DNA traits inherited from the hosts that birthed them, which means a Xenomorph hive and its population will be profoundly defined by the ecosystem that birthed it.

Praetorians could be considered an entirely different category, as they're considerably larger than other adult Xenomorphs (but still smaller than Queens). According to non-movie works, a handful of warriors are 'chosen' by the Queen and fed royal jelly, which leads to their transformation into the horrifying but majestic (due to the crown-like, flat crests) monstrosities tasked with protecting the leader of the hive.

Queen

The big boss and apex of the species is the Xenomorph Queen. Her highly iconic shape, coupled with the absolutely massive size for a terrestrial being, instantly granted Aliens' main villain a firm place among the best-ever monsters put on the big screen.

Queens are much larger and stronger than drones, warriors, and even praetorians. However, they're vulnerable while they're attached to the giant ovipositor that it uses to continuously lay eggs. They're not very fast, but can still surprise any unfortunate soul that isn't quick enough on their feet if they get agitated or are under extreme threat.

Video game and comic books have also introduced Empresses (Queens capable of ruling over several 'regular' Queens and their respective hives) and even the Queen Mothers, the absolute peak of the Xenomorph species, gigantic in size and far more intelligent than Empresses and Queens. As depicted in such works, the Queen Mothers can control all the Xenomorphs on a continent or planet. To this day, these definitive Xeno stages haven't been shown (or even referenced) in the movies, making them 'extended universe' additions.

Beyond the Xenomorph

Prometheus and Alien: Covenant, especially the former, put much of the focus on the Engineers and their other bioweapon efforts. Like it or not, the Xenomorphs in the current on-screen canon (which may clash with the Alien vs. Predator movies) are the product of the Engineers' experiments, much like mankind on Earth. The main weapon found by the unsuspecting humans and their Michael Fassbender-looking synthetics on LV-223 and Planet 4 was the 'black goo' that both created and destroyed life forms in unpredictable ways.

According to David's studies and experiments on Planet 4, an Engineer homeworld, the pathogen's primary purpose was to 'cleanse' planets of non-botanical life forms, yet the weapon proved to be more unstable than originally thought by its creators. Incompatible hosts were killed, and other beings were either mutated into monsters or became hosts for parasitic organisms similar to the Xenomorph facehugger. Unsurprisingly, those parasites also impregnated any living being that was big enough and produced alien lifeforms like the 'Deacon' on LV-223 and the 'Neomorphs' on Planet 4, which were remarkably close to the Xenomorphs as we know them.

While the main implication in Alien: Covenant is that David himself created the Xenomorph as seen in Alien and beyond after tinkering with the pathogen and the Engineers' scientific tools and knowledge, there are marked differences between the drones seen in the prequel and the one born from one of the eggs in LV-426. Moreover, the novelization of Covenant and some visual elements in the movie itself and the previous one offered enough wiggle room to consider that David could have simply revitalized an old Engineer bioweapon to create his own 'offshoot version' of the creature.

Word on the street is that Alien: Romulus might offer some answers for the remaining questions that the third Alien prequel was going to tackle, so maybe we'll end up with canon in a better place after Fede Álvarez's movie lands in August. However, the Alien TV series is supposedly set in a not-so-far future and on Earth, so chances are the flimsy lore will get even more complicated for diehard fans.

As great as A Quiet Place: Day One turned out to be, it didn't really shine more light on the extraterrestrial invaders beyond one key scene we'll discuss later, so the two 'main' A Quiet Place installments are more important to understanding what these monsters from outer space are, how they live, and what their end goal is. A closer look at those two movies, coupled with interviews with the key creatives and behind-the-scenes trivia paints a clearer picture of the aliens' nature. 

While we wait for official news on A Quiet Place Part III and whether or not it's directed by John  Krasinski, there's a surprising video game based on the movies coming our way sooner rather than later, and its reveal trailer is thrilling. Way before that, an even more nightmare-inducing alien species will be returning to the big screen in Alien: Romulus.  

Where are they from?

On Empire's podcast, all the way back in 2018, when the first movie was released, writer-director John Krasinski revealed much of the information that wasn't directly stated on-screen and confirmed numerous theories. Chief among them was the origin of the alien monsters, which he described as "predators" and "parasites" that "can’t be held back." 

According to the filmmaker, the main idea behind the monsters, their design and unique capabilities is that they're "an evolutionarily perfect machine," only that they come from a planet very different from ours. Their doomed world had no living creatures that resembled anything on Earth and no light, at least not in the way that our system has light. As a direct result, they evolved to hunt by sound and protect themselves from harsh environments and conditions, which explains why they can't be hurt unless "they open themselves up." 

Much like Krypton, the aliens' planet was destroyed, but most of the creatures managed to survive just fine floating adrift on (and inside) chunks of rocks across space for what we presume was a very long time. They're extremely resilient, seemingly don’t even need water and can survive the vacuum of outer space, so neither the destruction of the home planet nor crashing through Earth's atmosphere and on different points across the globe killed them off. 

Biology

Echolocation completely replaced sight as the species evolved on their planet of origin. On top of that, the aliens' skin is nearly impenetrable and armor-like; possibly a sign of the unknown world having much harsher conditions and higher gravity than Earth. The density of their bodies, however, makes them bad swimmers, and it's been proven they can drown. Therefore, many communities of survivors were established on islands. 

The creatures are slightly taller than humans; it’s their width that makes them bigger overall. The body posture kind of resembles that of gorillas and bats, and they seem to walk on their 'knuckles' rather than the end of their very long arms, which end on terrible three-finger claws used for hunting. In spite of their body density and very odd posture, they have proven to be extremely good climbers at fast speeds. On the ground, they can hit up to 300 miles per hour, so running away from them in a straight line and without turning their attention elsewhere is impossible. 

Though their heads hide a large jaw filled with fearsome teeth, it doesn't appear to be used as a weapon. Moreover, it hasn't been confirmed whether they can smell or not. They’ve got several ears protected by the head and face's armor-like plates, and it's been reported they're so sensitive they can even detect small clocks – under normal conditions – from hundreds of meters (if not miles) away. However, their biggest known weakness comes from that strength: naturally noisy environments or phenomena, such as waterfalls and rainstorms, can hide noises that would usually attract them, plus certain high-frequency sound waves can render them almost completely helpless. 

Do they eat humans?

The most baffling thing about these aliens is that they don't kill for food. In fact, they don't seem to consume any terrestrial organisms. This is hinted at in the very first movie, and human corpses are seen mummified and largely intact in most cases. The creatures instinctively hunt down and silence any other animal or thing that’s too noisy for them. 

So, how do they regain energy and stay fed? By and large, they seem to violate the laws of thermodynamics and physics, given their resilience to world-ending events and the vast emptiness of space, plus how fast and strong they are despite not consuming their prey for nutrients and energy. A Quiet Place: Day One, however, shows the creatures eating alien plants that also came with the asteroids and survived the interstellar trip. It's safe to assume – unless stated otherwise in a future entry – that these plants can reproduce as quickly as (if not more than) the creatures, which can't eat anything on Earth because of incompatible biologies. 

Behind the scenes

As it stands, the aliens don't have an official name in marketing materials or in-universe, but a newspaper clipping seen in the original movie calls them 'Death  Angels,' which is kind of fitting given their long, almost wing-like, arms and the fact they fell from the sky. 

The total population of 'Death Angels' on Earth hasn't been revealed either. We do know, however, that several asteroids hit U.S. soil, and their numbers in New York were far greater than in the less populated rural areas seen in the two mainline A Quiet Place movies. Their rate of reproduction and expansion hasn't been unveiled either, but the post-arrival timeline is only monthslong so far. Krasinski has stated in the past he's more interested in the more intimate stories happening during this apocalypse rather than making a traditional alien invasion movie, so we're not expecting to learn about global matters. 

Another fun fact about the 'Death Angels' is that Krasinski himself also provided some motion capture for them, with ILM handling the CGI and adding a few extra touches to the final design that came from ancient bog bodies.

That's according to a recent thought experiment in which scientists identified five "artificial" greenhouse gases that, if abundant enough, can be spotted in the atmospheres of certain exoplanets using existing technology, including the James Webb Space Telescope (JWST). 

The gases, which include fluorinated versions of methane, ethane, propane, on Earth are known to be some of the most potent and persistent heat-trapping gases emitted by humans during various industrial manufacturing processes, like those used to produce semiconductors, for instance. Because these substances don't naturally form in large quantities — if we're going by Earth chemistry, at least — spotting them in an exoplanet's air would signal the presence of technologically-advanced species, scientists say.

On Earth, these gases are dangerous pollutants, and limiting their emissions is crucial to combat human-driven climate change. Their presence in an alien atmosphere may not necessarily be bad news, however.

"For us, these gases are bad because we don't want to increase warming," study lead author Edward Schwieterman of the University of California, Riverside, said in a recent statement. "But they'd be good for a civilization that perhaps wanted to forestall an impending ice age or terraform an otherwise-uninhabitable planet in their system, as humans have proposed for Mars."

Related: NASA space telescope finds Earth-size exoplanet that's 'not a bad place' to hunt for life

 Such intentional climate modification to create an Earth-like environment is known as terraforming. The idea of terraforming Mars has sprouted in almost every sci-fi story, and, in recent years, scientists too have proposed similar approaches to support long-term colonization. Ideas to warm Mars include thawing some of the ice in the planet's poles and releasing carbon dioxide trapped in its surface to buttress the planet's thin atmosphere like a warm blanket. Although, some remain skeptical about the concept. For instance, Paul Sutter, an astrophysicist at SUNY Stony Brook and Space.com contributor, wrote in a 2021 article that this type of terraforming effort probably won't work, crucially because Mars likely doesn't host enough carbon dioxide to trigger a decent warming trend.

More recently, Schwieterman and his colleagues simulated a planet in the TRAPPIST-1 system, which is a family of seven rocky planets about 40 light-years away from Earth in the constellation Aquarius; several of them are considered potentially habitable. The planet, TRAPPIST-1f, for example, circles its host star every nine days within its habitable zone.

If aliens were to terraform such a planet, the researchers found the JWST could identify the five greenhouse gases. One among them, sulfur hexafluoride, has a warming potential that exceeds carbon dioxide by 23,500 times. Minuscule amounts of this gas, which has a lifetime of at least 1,000 years, is sufficient to thaw an icy planet to a point where life-supporting liquid water flows on its surface, the researchers say. (Life as we know it, to be clear).

"The long lifetime makes these gases excellent technosignatures to systematically search for in comparison to shorter-lived signals," study co-author Daniel Angerhausen of ETH Zürich said in another statement. "These signatures might even outlive their civilization if their geoengineering experiments were to fail."

Other similar, fluorinated gases may hover in an Earth-like atmosphere for up to 50,000 years, so "they wouldn't need to be replenished too often for a hospitable climate to be maintained," Schwieterman said in the statement. 

That means if extraterrestrial life in frigid planets beyond our solar system pumps a bunch of greenhouse gases into their atmospheres to make their worlds more habitable, our existing telescopes might be able to spot them. Even if only one out of every million gas molecules sucked in infrared radiation from its host star, it would produce a tell-tale signature detectable with the JWST and other space-based telescopes, Schwieterman and his team found. 

"You wouldn't need extra effort to look for these technosignatures, if your telescope is already characterizing the planet for other reasons," said Schwieterman. "And it would be jaw-droppingly amazing to find them." 

These findings are described in a paper published June 25 in The Astrophysical Journal.

Michael Garrett is the Sir Bernard Lovell chair of Astrophysics and Director of Jodrell Bank Centre for Astrophysics, University of Manchester.

Artificial intelligence (AI) has progressed at an astounding pace over the last few years. Some scientists are now looking towards the development of artificial superintelligence (ASI) — a form of AI that would not only surpass human intelligence but would not be bound by the learning speeds of humans.

But what if this milestone isn't just a remarkable achievement? What if it also represents a formidable bottleneck in the development of all civilizations, one so challenging that it thwarts their long-term survival?

Related: Could AI find alien life faster than humans, and would it tell us?

This idea is at the heart of a research paper I recently published in Acta Astronautica. Could AI be the universe's "great filter" – a threshold so hard to overcome that it prevents most life from evolving into space-faring civilizations?

This is a concept that might explain why the search for extraterrestrial intelligence (SETI) has yet to detect the signatures of advanced technical civilizations elsewhere in the galaxy.

The great filter hypothesis is ultimately a proposed solution to the Fermi Paradox. This questions why, in a universe vast and ancient enough to host billions of potentially habitable planets, we have not detected any signs of alien civilizations. The hypothesis suggests there are insurmountable hurdles in the evolutionary timeline of civilizations that prevent them from developing into space-faring entities.

I believe the emergence of ASI could be such a filter. AI's rapid advancement, potentially leading to ASI, may intersect with a critical phase in a civilization's development – the transition from a single-planet species to a multiplanetary one.

This is where many civilizations could falter, with AI making much more rapid progress than our ability either to control it or sustainably explore and populate our Solar System.

The challenge with AI, and specifically ASI, lies in its autonomous, self-amplifying and improving nature. It possesses the potential to enhance its own capabilities at a speed that outpaces our own evolutionary timelines without AI.

The potential for something to go badly wrong is enormous, leading to the downfall of both biological and AI civilizations before they ever get the chance to become multiplanetary. For example, if nations increasingly rely on and cede power to autonomous AI systems that compete against each other, military capabilities could be used to kill and destroy on an unprecedented scale. This could potentially lead to the destruction of our entire civilization, including the AI systems themselves.

In this scenario, I estimate the typical longevity of a technological civilization might be less than 100 years. That's roughly the time between being able to receive and broadcast signals between the stars (1960), and the estimated emergence of ASI (2040) on Earth. This is alarmingly short when set against the cosmic timescale of billions of years.

This estimate, when plugged into optimistic versions of the Drake equation – which attempts to estimate the number of active, communicative extraterrestrial civilizations in the Milky Way – suggests that, at any given time, there are only a handful of intelligent civilizations out there. Moreover, like us, their relatively modest technological activities could make them quite challenging to detect.

Wake-up call

This research is not simply a cautionary tale of potential doom. It serves as a wake-up call for humanity to establish robust regulatory frameworks to guide the development of AI, including military systems.

This is not just about preventing the malevolent use of AI on Earth; it’s also about ensuring the evolution of AI aligns with the long-term survival of our species. It suggests we need to put more resources into becoming a multiplanetary society as soon as possible – a goal that has lain dormant since the heady days of the Apollo project, but has lately been reignited by advances made by private companies.

As the historian Yuval Noah Harari noted, nothing in history has prepared us for the impact of introducing non-conscious, super-intelligent entities to our planet. Recently, the implications of autonomous AI decision-making have led to calls from prominent leaders in the field for a moratorium on the development of AI, until a responsible form of control and regulation can be introduced.

But even if every country agreed to abide by strict rules and regulation, rogue organizations will be difficult to rein in.

The integration of autonomous AI in military defense systems has to be an area of particular concern. There is already evidence that humans will voluntarily relinquish significant power to increasingly capable systems, because they can carry out useful tasks much more rapidly and effectively without human intervention. Governments are therefore reluctant to regulate in this area given the strategic advantages AI offers, as has been recently and devastatingly demonstrated in Gaza.

This means we already edge dangerously close to a precipice where autonomous weapons operate beyond ethical boundaries and sidestep international law. In such a world, surrendering power to AI systems in order to gain a tactical advantage could inadvertently set off a chain of rapidly escalating, highly destructive events. In the blink of an eye, the collective intelligence of our planet could be obliterated.

Humanity is at a crucial point in its technological trajectory. Our actions now could determine whether we become an enduring interstellar civilization, or succumb to the challenges posed by our own creations.

Using SETI as a lens through which we can examine our future development adds a new dimension to the discussion on the future of AI. It is up to all of us to ensure that when we reach for the stars, we do so not as a cautionary tale for other civilizations, but as a beacon of hope – a species that learned to thrive alongside AI.

Originally published at The Conversation.

The SpaceX CEO and founder sat down for a panel titled "How to save the human race and other light topics" at the 2024 Milken Institute Global Conference held in Los Angeles on Tuesday (May 7). During the conversation, the institute's chairman, financier Michael Milken, began by asking Musk how he feels about the well-known opening monologue to many "Star Trek" series, in which it is stated that the starship Enterprise's mission is to "seek out new life forms and new civilizations." Musk replied, "Yeah, that's the idea."

Musk elaborated, stating that if we send probes out into the universe, we might find "remains of long-dead alien civilizations." He then launched into an explanation about why he doesn't feel aliens have ever visited our planet.

Related: SpaceX's Starship will go interstellar someday, Elon Musk says

Musk told Milken that he is frequently asked if he believes aliens are among us here on Earth, acknowledging how widespread that belief is. "And for some reason, a lot of the same people who think there are aliens among us don't think we went to the moon, which, I'm like: 'Think about that for a second,'" Musk said to laughter from the audience.

Musk elaborated on why he doesn't believe aliens have visited our planet, stating that, even with the thousands of broadband spacecraft that SpaceX operates in low Earth orbit, he hasn't once seen any compelling evidence of either extraterrestrial life or any potential craft operated by non-human intelligence.

"I've not seen any evidence of aliens," Musk said. "And SpaceX, with the Starlink constellation, has roughly 6,000 satellites, and not once have we had to maneuver around a UFO. [...] Never. So I'm like, okay, I don't see any evidence of aliens."

But, like many people, Musk said that he's open to considering the possibility of alien visitation, if indeed there is any compelling proof. "If somebody has evidence of aliens, you know, that's not just a fuzzy blob, then I'd love to see it, love to hear about it," Musk said. "But I don't think there is."

The SpaceX CEO then pointed out how concerning the lack of any evidence of alien civilizations is for the future of humanity, opining that, even if an ancient civilization managed to last a million years, it should have easily been able to explore and settle the entire Milky Way galaxy.

"So, they haven't, so why not?" Musk asked.

"I think the answer might be, probably, is that that civilization is precarious, and rare. And that we should really think of human civilization as being like a tiny candle in a vast darkness. And we should do everything possible to ensure that that candle does not go out."

Despite having never had to move out of the way of a UFO, Starlink satellites do, in fact, regularly make avoidance maneuvers to dodge debris or other spacecraft. Between June 1, 2023, and Nov. 30, 2023, Starlink satellites performed 24,410 collision avoidance maneuvers, equivalent to six maneuvers per spacecraft, according to data collected by SpaceX reported to the U.S. Federal Communications Commission (FCC).

"Alien Day" (April 26) has arrived, that annual occasion for all xenomorph acolytes to immerse themselves in the legends and lore of the storied "Alien" franchise that first hatched way back on May 25, 1979 to create one of the most frightening cinematic universes in Hollywood history. 

Officially promoted by 20th Century Fox beginning in 2016, Alien Day gets its name from the designation numerals of the LV-426 planetoid where "Alien's" space truckers discover a nightmarish derelict spaceship housing a horrifying secret. 

Related: Alien movies in order: chronological and release

Now for a limited time starting April 26, in honor of the 45th anniversary of 'Alien,' multiplex audiences can re-experience the sheer terror in a darkened theater once again, surrounded by petrified fellow patrons to witness the crew of the commercial towing vessel Nostromo being stalked by a marauding biomechanical creature with no conscience and concentrated acid for blood.

Directed by a youthful Ridley Scott from an original screenplay by Dan O’Bannon and Ron Shusett, "Alien's" stellar cast included Tom Skerritt, Sigourney Weaver, Yaphet Kotto, Veronica Cartwright, Harry Dean Stanton, John Hurt, and Ian Holm. Fans attending these special anniversary screenings will also be treated to an engaging conversation between Ridley Scott and Fede Alvarez, the director/writer of this summer's theatrical release, "Alien: Romulus."

In other Alien Day news, an upcoming documentary titled "Aliens Expanded" seeks to crack open the memories behind the making of James Cameron's 1986 "Alien" sequel and we have an exclusive chat with its director, British filmmaker Ian Nathan.

Here's the official description:

'Join the 'Aliens' cast & crew, including James Cameron (Writer & Director), Gale Anne Hurd (Producer), Michael Biehn (Hicks), Lance Henriksen (Bishop)  Mark Rolston (Drake), Jenette Goldstein (Vasquez), William Hope (Gorman) and Carrie Henn (Newt), on a deep dive into this science-fiction classic. Brimming with stories, insight, and wonderful personal detail, this four-hour documentary is the most passionate and sophisticated exploration of 'Aliens' ever made; a love letter to the people who made it and the communities who adore it, reflecting and enhancing the incredible legacy of this beloved epic."

London-born director Ian Nathan first saw "Aliens" when he was sixteen with his dad, in a hot cinema full to the brim, and he’s still not sure that he’s ever had an equivalent experience. His goal was to create an in-depth exploration of Cameron's iconic film and discover new info and insights along the way with the cast and crew.

"I was enslaved to that film, gripped like a vice," Nathan tells Space.com. "After the med-lab scene with the facehuggers, right up until the power loader, I had to remind myself to breathe. It was that thrilling. But I have come to understand that so much of that immersion is because James Cameron made me care so much about those characters. Beyond its place as a science fiction great, and a horror great, it is a perfect character piece. And even now, having seen it countless times, if I catch it on the box, I am there to the end, still willing them to survive." 

Having Cameron on board to share never-heard tales of his trials, tribulations, and purity of vision in making "Aliens" was a true masterclass in filmmaking for Nathan. When asked to recall his favorite scene in the 1986 classic, he's quick to respond.

"This is easy. I've known it since the night I first saw the film," he explains. "It's the crucial scene in the film, because this is when Ripley takes charge. Not because she wants to, but because she has to. She is a born leader. The marine incursion into the nest has gone to hell, chaos reigns, and Gorman is cracking up. Ripley is screaming at him. 'Do something!' Then she throws off her headset, secures Newt, and takes control of the APC. The drums kick in on the soundtrack and she rams that thing into the nest to rescue whichever survivors she can. It's Ripley's mission now." 

Fans can order "Aliens Expanded" by May 5 to get their name placed in the credits and score exclusive merchandise, with an expected June digital delivery date and physical copies coming in July.

For astronomers like me, this question has proved tricky — so tricky that we were very nearly fooled when the first recorded interstellar object, named 'Oumuamua, was spotted passing through the inner solar system in 2017.

Astronomers once thought that any object moving under its own speed, with no visible means of propulsion, would have to be artificial technology. We knew how 'Oumuamua should behave if it were an interstellar space rock, or so we thought, but in every way it acted the exact opposite. 

Related: 'Oumuamua: The solar system's 1st interstellar visitor explained in photos

As 'Oumuamua sped through the solar system, we only had a few weeks during which we were able to monitor it with our telescopes across the world. These observations showed that the object came from outside the solar system, and was extremely elongated and tumbling. 'Oumuamua displayed no comet-like tail but still moved under its own propulsion. 

Comets also move under their own propulsion, but they display beautiful tails caused by dust and ice blown off their surfaces, which also causes a rocket-like recoil. 'Oumuamua was different. Its mysterious flight through our solar system sparked whispers of an artificial provenance. Some astronomers even called it Rama.  

The true explanation, which we determined from its motion and the amount of energy it received from the sun, is just as strange: an entirely new kind of object. We call them "dark comets." Since we spotted 'Oumuamua, we have found a population of seven dark comets hiding among our solar system's asteroids. They get their name because they move like a comet, but display no dust tail.  

Visitors from beyond the solar system — interstellar travelers — have long been predicted by science fiction writers like Arthur C. Clarke, but in reality, it's not so easy to identify what we're seeing — or just how many interstellar space rocks, or spaceships, are in Earth's neighborhood at a given time. This difficulty came to a head as we rushed to make sense of 'Oumuamua, but with new telescopes like the James Webb Space Telescope (JWST) and the forthcoming Rubin Observatory Legacy Survey of Space and Time (LSST) in the Atacama Desert in Chile, we'll have the tools we need to make sense of future interstellar travelers — and expand our understanding of the cosmos.  

If only we'd had the JWST when 'Oumuamua was discovered, we would have been able to take more detailed images of the object and get information about how it looked in different wavelengths of light. By doing this, we could have better understood what was propelling it through space. We would have seen molecules like water or carbon dioxide that only show up at certain wavelengths and don't reflect sunlight. We routinely see normal solar system comets being propelled as their surfaces heat up and water and carbon dioxide ice transform into gas. We would have identified it immediately as a dark comet-like object. The good news is, if we spot another 'Oumuamua, we already have an approved JWST program to monitor it.  

Related: James Webb Space Telescope (JWST) — A complete guide

In the future, the JWST won't be the only powerful tool in our toolkit. The LSST, set to come online in the next year or so, should detect many more interstellar objects and be able to identify dark comets in our own solar system. Located in the Atacama Desert, a prime spot for viewing the heavens, the LSST will start scanning the entire Southern Hemisphere sky almost every night. The LSST will be able to spot much fainter objects than any of our surveys that currently monitor the entire sky for rapidly moving objects. It will be able to detect mysterious objects like 'Oumuamua that are dimmer, either because they are smaller or farther away from the Earth. The LSST will also be able to find many more smaller asteroids, and will be able to spot if they are dark comets and moving under their own propulsion. 

It's possible that when the LSST makes first light, we will start detecting interstellar objects on a monthly — or even weekly — basis. Some of these may be dark like 'Oumuamua, and some may be brighter with beautiful tails, like the second interstellar comet, 2I/Borisov.   

It may turn out that the sky close to the Earth is teeming with interstellar objects even smaller than 'Oumuamua, all of which were invisible up until now. These small interstellar visitors could quite plausibly be continuously whizzing through the Earth's neighborhood within the solar system. If that ends up happening, then the LSST might spot an interstellar target close enough for a dedicated space mission.  

Close encounters with an interstellar visitor will no longer be a topic reserved for science fiction writers. 

With the LSST and JWST, we have the tools to tell the difference between an intelligent visitor and an interstellar dark comet. Let's not get fooled. 

Darryl Seligman is a research associate in the Department of Astronomy at Cornell University. His research focuses primarily on theoretical and computational planetary science and astrophysics. 

Biologists, anthropologists, linguists and other experts specializing in language and communication have begun to explore what non-human, off-Earth language might look like. 

Arguably, such thinking sparks thought about the fabricated Klingon language, the cosmic "Klingonese" chatter spoken by one the alien species on "Star Trek." There's even a thriving Klingon Language Institute, which was founded in 1992.

But you can put sci-fi aside, for scientists in the real world are investigating the possible forms that alien languages might take — and whether we might be able to understand them.

Related: The search for alien life

Off-Earth intelligence

Astrobiologist Douglas Vakoch is president of Messaging Extraterrestrial Intelligence (METI International) in San Francisco. He's co-editor with Jeffrey Punske of a new volume, "Xenolinguistics: Towards a Science of Extraterrestrial Language" (Routledge Taylor & Francis Group (2023).

The book is anchored in what is known about human language and animal communication systems, but it offers suggestions about what we may find if we encounter non-Earth intelligence.

For over six decades, researchers have been engaged in the search for extraterrestrial Intelligence (SETI), listening for signals with radio telescopes — and they could succeed tomorrow, Vakoch told Space.com. (METI, as its name suggests, concerns the possibility of communicating with alien intelligence — making meaningful contact.)

"We might be faced with understanding a message from an unknown civilization, and linguists could provide the key to cracking the code," said Vakoch. "The recommendations coming out of our new book are directly shaping how we will say 'Hello, universe.'"

Vakoch highlighted the importance of communicating our intentions as the hallmark and rationale for METI messages. "Another key question is whether universal grammar of the sort we see across languages on Earth will also hold true more broadly in the universe," he says.

As noted in the volume, one major point is that communication involves more than getting across the content of your message. "You also want to communicate your intention," said Vakoch.

Related: If aliens have visited the solar system, here's how to find clues they left

Start a conversation

One of the common objections to METI, Vakoch pointed out, is that we may alert hostile extraterrestrials to our existence and provoke an alien invasion. 

"In reality, any civilization with the capacity to travel between the stars also has the technology to pick up the accidental radio and television signals that have been leaking off into space for the past century," Vakoch said. 

So any aliens picking up our targeted messages won't be surprised to know we exist, Vakoch added. "But what will surprise them is that we're attempting to start a conversation. That's the whole point of METI — to get across our intention of making first contact."

Universal principles

Vakoch said that the aliens he is most interested in are the ones we can make contact with. 

"Those are the aliens who have developed the technology to transmit and receive radio signals. In the past, when scientists have sent interstellar messages, this shared technology has provided the foundation for crafting the messages." 

The messages we've sent into space so far have relied on possibly universal principles of math and science as a starting point, said Vakoch. "But maybe there's something more basic. Long before humans had math and science, we had language. Maybe the same is true on planets orbiting other stars."

In the end, Vakoch thinks, the idea that we must choose between either math and science, on one hand, or language, on the other, is itself too simplistic.

Core of language

Co-editor of the new xenolinguistics book is Jeffrey Punske, an associate professor and the director of undergraduate studies in linguistics at Southern Illinois University in Carbondale. 

What we define as the core of language may be fundamentally constrained by external considerations. If so, then it is almost certain that a linguistic, non-human intelligence would have the same core of language, Punske suggests. 

"However, there are many aspects of language that are universal to human language that cannot solely be attributed to such externals," he said. "Those aspects are likely products of the structure of human cognition. There is certainly no guarantee that a non-human intelligence would share our cognitive systems. Thus, while the underlying structure of language might be the same, the message might not be interpretable."

New perspective

Excited that scientists are beginning to think seriously about xenolinguistics is Bridget Samuels of the University of Southern California (USC). 

Samuels is conducting research in two areas that address where universal grammar may fit in the universe: How did language arise in our species, and what are the limits of variation in human language? 

"The study of animal communication has exploded in recent years, and it's given us a new perspective on how human language is, and isn't, unique," Samuels, the project director at USC's Center for Craniofacial Molecular Biology, told Space.com. "Also, how communication systems are shaped by the unique cognitive abilities of the organisms that use them, as well as by the environmental niches they inhabit." 

Invariant laws of physics

Those lines of inquiry, combined with a "third factor" in language design — factors that shape language beyond our genetic endowment and experience — have set the stage for theorizing in entirely new ways about universal grammar, Samuels said.

That theorizing has helped Samuels shape and share a prediction with Punske: "Some aspects of language syntax and externalization may even be shared by extraterrestrial languages, as they are constrained by invariant laws of physics."

By pondering language and animal communication in a cosmic context, Vakoch said, we are forced to rethink just how unique language is, even on our own planet — whether or not we ever make contact with extraterrestrials. 

"Xenolinguistics shows that human language may not have the privileged position we've always assumed," he said.

This was the message that a group of Kentucky scientists, linguists and scholars recently beamed at the TRAPPIST-1 system, which lies 40 light-years from Earth and harbors multiple potentially habitable planets.

The missive represented the very first interstellar travel advertisement, according to VisitLEX, the group behind the effort.

Related: The search for alien life

VisitLEX's tourism team at the Lexington Convention and Visitors Bureau partnered with the Cornett ad agency to devise a playful campaign with sci-fi flavor. The team used a modified infrared laser to deliver a specially coded message, which was approved by the U.S. Federal Aviation Administration. 

Here are details from the VisitLEX press release:

"When the message reaches its destination in 2063, TRAPPIST-1 inhabitants will find a coded bitmap image with clues as to its origin and intent of the transmission. They'll also see bucolic photos of the Horse Capital of the World, noting the wide-open spaces perfect for landing a spacecraft. They'll learn why Lexington has the best food, bourbon and music on Earth — getting a taste via an audio recording from legendary blues musician Tee Dee Young."

If E.T. does eventually receive the message and pack their bags for our solar system, eager to take in The Bluegrass State's hospitality, thoroughbred race horses and bourbon industry, they'll have to cover 235 trillion miles (378 trillion kilometers) to get here. That's a bit of a trip, but who knows how fast their craft can go?

"We are targeting the TRAPPIST-1 system because we might actually get an answer in somebody's lifetime if there's somebody there watching," said astrobiologist and SETI (search for extraterrestrial intelligence) scientist Robert Lodder. "But the reason scientists have been interested in it lately is because of the large number of planets it has in what is considered to be the habitable zone. So, there could be life there. Why not send a signal and see if they answer?"

This message was sent last month from Lexington's Kentucky Horse Park museum and event center, during a festive evening ceremony that drew a sign-waving crowd. 

"The bitmap image is the key to it all. We included imagery representing the elements of life, our iconic Lexington rolling hills and the molecular structure for water, bourbon and even dopamine … because Lexington is fun!" added linguistics expert Andrew Byrd.

First of all, the consequences of first contact strongly depend on the way it takes place. The paper offers the view that first contact with alien life poses considerable risks for humanity. Additionally, a first contact event could also take place without being culturally recognized.

The intriguing new research paper is led by Andreas Anton of the Institute for Frontier Areas of Psychology and Mental Health in Freiburg, Germany.

Related: The search for alien life

Scenarios

Anton and colleagues serve up a set of scenarios:

• The signal scenario is the basis of SETI (search for extraterrestrial intelligence) programs, in which radio astronomers search for signs of alien civilizations. It assumes that radio telescopes can pick up artificial signals from the far reaches of space.
• The technosignature scenario envisions that future powerful telescopes will find evidence of past or present extraterrestrial technology.
• The artifact scenario assumes that one day, somewhere in our solar system (or even on Earth itself), we will come across the material remains — such as a space probe — of an extraterrestrial civilization.
• The encounter scenario involves the appearance of an alien spacecraft in near-Earth space that can be assumed, based on its flight maneuvers or other actions, to be controlled by intelligence, either biological or artificial.

Biological beings or artificial intelligence?

The prospect of an encounter scenario, the paper points out, raises an important question: Whether the alien technology is controlled by a biological life form or an artificial intelligence.

"A biological life form, we suspect, could potentially cause greater anxiety, as the immediate question would be what 'they' want here. It also has an inbuilt assumption that they have a relatively nearby base or have superfast travel (maybe faster than light) and would thus be very far ahead of us technologically," Anton and co-authors write in their paper. 

"However, the question of whether the encounter is with a biological life form or the emissaries of a machine civilization could remain unresolved for a long time," they add.

Be prepared

The paper concludes by acknowledging that the more we know about the universe and the further we penetrate into the cosmos through our own research activities, "the more likely it is that we will be confronted with alien civilizations, their signals or their legacies."

That being the case, the researchers suggest, humanity needs to be prepared as a global society for this scenario.

"In the political sphere, the question of how to deal with this discovery and possible communication with extraterrestrial civilizations would lead to a global discourse," they write in the paper. "International cooperation would be essential to develop a unified approach to dealing with this new reality."

 This research paper, titled "Meeting extraterrestrials: Scenarios of first contact from the perspective of exosociology," is available here. 

Researchers from the SETI Institute, University of California Davis and the Alaska Whale Foundation recently "conversed" with a humpback whale named Twain using an underwater speaker and recorded a humpback "contact" call. Twain responded to the researchers' call by matching the interval variations between signals of each playback call over a 20-minute period. 

If you're having a Star Trek flashback, yes, this is awfully reminiscent of that one film in which the crew receives alien whale transmissions that can only be decoded underwater. And in fact, mirroring our sci-fi fantasies, this demonstration of interspecies communication has implications for the search for extraterrestrial intelligence, according to a statement from the SETI Institute. 

"We believe this is the first such communicative exchange between humans and humpback whales in the humpback ‘language,'" Brenda McCowan, lead author of the study from U.C. Davis, said in the statement. 

Related: Why are we still searching for intelligent alien life?

Much like how astronaut crews simulate missions to Mars or the moon on Earth, the Whale-SETI team is studying humpback whale communication systems to better understand how to detect and interpret signals from outer space. Their findings can be used to develop filters that can be applied to any extraterrestrial signals received, according to the statement. 

"Because of current limitations on technology, an important assumption of the search for extraterrestrial intelligence is that extraterrestrials will be interested in making contact and so target human receivers," Laurance Doyle, coauthor of the study from the SETI Institute, said in the statement. "This important assumption is certainly supported by the behavior of humpback whales."

Twain's response to each playback call showcases a sophisticated level of understanding and interaction. The humpback whale approached and circled the team’s boat upon hearing the contact call played via an underwater speaker. Matching the interval variations between each call mirrors a human-like conversational style, according to the study. 

"Humpback whales are extremely intelligent, have complex social systems, make tools — nets out of bubbles to catch fish — and communicate extensively with both songs and social calls," Fred Sharpe, co-author of the study from the Alaska Whale Foundation, said in the statement. 

Therefore, working with humpback whales offers a unique opportunity to study intelligent communication in non-human species. The team will apply principles of information theory to develop filters that can aid in processing extraterrestrial signals and the search for intelligent life beyond Earth.

Their findings were published Nov. 29 in the journal PeerJ.

Last summer, Harvard astrophysicist and extraterrestrial hunter Avi Loeb declared that several tiny, metallic balls dredged up from the bottom of the ocean were likely remnants from an interstellar meteorite, and could even contain signatures of alien technology. Now, independent analysis suggests the spheres have a much less distant origin: They are more likely a by-product of burning coal on Earth.

Related: 'Galileo Project' will search for evidence of extraterrestrial life from the technology it leaves behind

Loeb and his colleagues found the micrometer-sized spherules during an expedition off the coast of Papua New Guinea in search of fragments of a meteor that streaked through the atmosphere in 2014.

Based on the meteor's recorded speed, Loeb and his team said that it was likely interstellar in origin — and that it must have left debris in its wake. The dredged-up spheres, they suggested, are that debris, as their composition is different from that of most meteorites.

In several blog posts and a non-peer-reviewed paper posted to the preprint database arXiv, Loeb described the various "anomalous" properties of the metallic pellets. He zeroed in on five spherules in particular that contained a high percentage of beryllium, lanthanum and uranium. Loeb dubbed these five "BeLaU spherules". He and others have since speculated that the weird spheres might be evidence of alien technology.

But many scientists unrelated to the research took issue with these claims at the time — and now, several newly published studies poke additional holes in the supposed extraterrestrial origins of the spherules.

Interstellar rock, or manmade pollution?

First, there is some debate as to whether or not the meteor in question was actually interstellar. It was only recorded by U.S. military equipment, and some researchers say that it's possible the sensors made a mistake when recording its speed, according to a new non-peer-reviewed paper posted to arXiv on Nov. 13. However, even if the meteor's speed was correctly recorded, odds are low that any significant pieces of it would survive the fall through the atmosphere.

"If interstellar, practically none of the 2014-01-08 bolide would have survived entry," the authors of the new study — professors Steven Desch of Arizona State University and Alan Jackson of Towson University — wrote. "If it were traveling at the speeds that were reported (and necessary to be interstellar), then at least 99.8%, and probably > 99.9999% of it would have vaporized in the atmosphere, leaving insignificant quantities to be deposited on the seafloor."

Then, there's the issue of proving the spheres came from that particular meteor. Scientists don't know where or even whether the 2014 meteor landed; it would be extremely difficult to find tiny pieces of that exact specimen by searching the ocean within a 30-mile (48 kilometers) radius nearly 10 years after it appeared. On the other hand, little metal balls are ubiquitous on the seafloor. Some are micrometeorites shed by passing space rocks, but others are spewed out by volcanoes or produced by industrial activity. These naturally collect at the bottom of the ocean over time.

Finally, there is the question of the spheres' makeup.  If you start from the assumption that these particular pellets originated in space, then their composition does indeed seem unusual. However, as a recent paper published Oct. 23 in the journal Research Notes of the AAS points out, they match the profile of coal ash contaminants. Study author Patricio Gallardo, an astronomer at the University of Chicago, wrote that, because of this, "the meteoritic origin is disfavored."

Is it still possible that the spherules came from somewhere outside our solar system? Yes. But, based on the available evidence, it appears far more likely that they originated much closer to home, the new papers suggest. As NASA astrobiologist Caleb Scharf wrote on X, formerly known as Twitter, "Well, they did indeed discover evidence of a technological civilization…right here on Earth."

Loeb refutes critics

Loeb responded to these criticisms in a Nov. 15 blog post on Medium, arguing that the new papers cannot adequately assess the composition of the spherules without studying them directly.

He went on to quote team member Jim Lem of the Papua New Guinea University of Technology, writing: "The region where the expedition was carried, should have no coal mineralization. In addition, coal is non-magnetic and cannot be picked up by the magnetic sled that was used."

Loeb added that 93% of the collected samples have yet to be analyzed, cautioning critics not to jump to conclusions about their origins until all the data is in. To make definitive claims about the spherules' nature before they are properly analyzed in a peer-reviewed study would be "unprofessional," Loeb said.

It's a question we've all wondered. Given all of the advances in space telescopes, robotic missions to other planets and even the wild headlines related to UFOs and possible extraterrestrial visitation these days, the question can seem more pressing than ever. And for children, the question can feel frightening, fascinating and everything in between, given some of the sensationalism that surrounds the subject.

To help sort out fact from fiction, author and podcast host Laura Krantz has written "Is There Anybody Out There?: The Search for Extraterrestrial Life, from Amoebas to Aliens," a new book from Abrams Books for Young Readers coming out on Oct. 3, 2023. The book takes a rational look at the search for extraterrestrial intelligence, the flyby of interstellar object 'Oumuamua and even well-known examples of UFO lore like the July 1947 crash of either a flying saucer or a secret U.S. military balloon outside Roswell, New Mexico,

Space.com spoke with Krantz to learn about the book, her take on the UFO buzz these days and even some tips on how to talk to kids about aliens.

Related: The search for alien life

Space.com: First off, I have to say that this is a beautifully illustrated book.

Laura Krantz: I just love it. I love the colors. I love this sort of like blocky illustration style. I just I think it turned out really, really well. [Illustrator Rafael Nobre] has a good sense of humor, too. Like he's able to incorporate some of the funnier stuff into like, great photos. Like there's the scene of an alien trying to cook life, I just I love that one.

Space.com: What was the inspiration for the book?

Krantz:  The book is really a spin-off of the Wild Thing podcast. When I started doing the podcast, I wasn't really thinking about kids at all, I was thinking about adults. And I started getting letters from parents who were listening with their kids, teachers who were using elements of the podcast in their classroom to talk about like, evolution, DNA evidence and the scientific method. And I started talking to my agent, and she suggested doing a middle-grade nonfiction book, because that is really an area where teachers love this kind of information and resources for kids. 

But it's interesting to write this kind of stuff. Because when you're doing it for an adult audience, you assume they know what DNA is, they know what evolution is. They know what all these sort of terms mean, at least sort of obliquely. But when you're writing for kids, you're like 'Crap, I have to understand what this actually is, and be able to explain it in plain language!' So it was like getting a crash course in science education.

Space.com: Why do you think it's important for young people to read this book?

Krantz: I think one of the most important things about it is that [the question of alien life] kind of sits firmly in the gray area. There's no answer to the question "Is there anybody out there?" Just like there's no answer to the Bigfoot question. It's like, this is an area to explore. This is an area to think about things scientifically and wonder and hypothesize. And guess what? We don't have a solid answer. 

And in some ways, it's like teaching kids to be comfortable with the idea that there's no answer, because I think we are in a society now where things tend to be pretty black and white, good or bad, right or wrong, one side or the other side. And with this, you just kind of have to be like, 'There might be aliens out there; I can see both sides of this argument.' I can see all different ways this might go. And I still don't know for sure. And I think that that's valuable. 

And then I think the other thing, too, is it's helpful to help. It's helpful for kids to see how science works, that science has such a long timeline, that the work that was done in the '50s and '60s and '70s on space science, many of those scientists aren't around or won't be around to see where the sort of seeds that they planted end up. And I think that that's sort of important for kids to understand — that science is constantly building on itself and revising and resubmitting, and trying to figure it out as best as it can using the evidence at the time. I think those are two really valuable things. 

And then, also, space is cool.

Space.com: I read in your introduction like you were not familiar with the UFO topic before getting into this, right?

Krantz: What really caught my attention was, firstly, the 'Oumuamua story, which I just thought was fascinating. I mean, we guessed that there were things coming in from outside our solar system. But we hadn't really been able to say that for sure. And this is the first moment we were like, 'This thing is from very far away.' And I think that that's just kind of a cool thing to think about — like, this moment in time, we have this realization of just how big the universe is, and what kinds of things are traveling through it. 

And also seeing photos coming out of the James Webb Space Telescope. And granted this that was after this project was mostly finished. But it's hard not to look at those photos and just have your jaw drop with, you know, how amazingly beautiful and yet, kind of terrifyingly awesome they are. A lot of those photos make you feel very small and insignificant, which is, I guess, kind of a good reminder of our place. And in the grand scheme of things.

Space.com: What do you make of the current UFO buzz in the U.S. government?

Krantz: I saw how, like, crazy, everybody went over the AATIP program [an alleged U.S. Department of Defense UFO study program]. And when the announcement came out about that, like, people lost their marbles; the headlines on that were just constant. And so that was the moment where I was like, 'There's something to be done here on this' and sort of take my glancing interest in it and pull in these threads where it's obvious that this is a question that people think about a lot, even if it's not something we're talking about day to day.

I think that it's a perfect opportunity to apply some rational thought. So, for instance, the whistleblower who testified in front of Congress, he said that people told him that they had recovered bodies, but he hadn't seen them for himself. So that to me is the first red flag. It's like, if you're the whistleblower, you need to have been seeing some of the stuff, you can't just use hearsay. Generally, that's not admissible in court, from what I understand about legal proceedings. So I think that should be a rational thing. And in science, too, and in scientific inquiry.

I don't doubt that there's some weird stuff up in the sky, and that pilots are seeing things. I do think there needs to be a recording process for that, that does not have a stigma attached to it. 

Related: UFOs and UAP: History, sightings and mysteries

Space.com: What do you hope kids take away from the book?

Krantz: That wonder is a huge asset. I think it's so valuable. And I think we kind of beat the wonder out of people as they become grownups. It's like, there's these boxes, you have to check in these things you have to do and the wonder kind of slips by the wayside. But wonder is so important, because it gets you figuring out how your world works. And it gets you thinking about things from different perspectives. And scientifically, like the first step of the scientific method is, it's about wonder. Ask a question; what are you wondering? And I think that that is a really valuable thing for kids. 

And I also think it's a valuable thing for adults to wonder about the world around you, to wonder about what life is like for other people to just sort of have this curiosity and questions and continuing to maybe question your own thoughts on things and beliefs. And, you know, it extends beyond science. I think wonder is a skill that we sometimes lose as we get older.

"Is There Anybody Out There?: The Search for Extraterrestrial Life, from Amoebas to Aliens," is currently available for pre-order and will be released on Oct. 3, 2023.

Unfortunately, this is not because a mothership landed on the White House lawn, but because NASA released a long-awaited report published by the independent study team the agency commissioned to study unidentified anomalous phenomena (UAP). UAP is the new term for UFOs, encompassing not only unexplained things in the air but also in space, under water and everywhere in between.

However, the release of NASA's first UFO report wasn't the only story about possible non-human lifeforms to make headlines this week. According to Reuters, lawmakers in Mexico heard testimony this week about the presence of alien life on Earth that included two "corpses of extraterrestrials." These alleged alien corpses looked "white and like stereotypical depictions of aliens — big head, little body, three fingers," NPR reported.

The supposed alien mummies (well, the creepy ... whatever they are) were displayed by Jaime Maussan, a longtime UFO personality with a history of hoaxing alleged non-human remains. Despite Maussan's history of faking alien corpses and mummies, the story has now gone wide — so wide, in fact, that it was brought up during NASA's briefing about the new UAP report which took place on Thursday (Sept. 14). 

Related: NASA UFO report finds no evidence of 'extraterrestrial origin' for UAP sightings

During Thursday's briefing, BBC News Digital journalist Sam Cabral asked whether or not NASA has been in touch with Mexican authorities about "the rather sensational revelations" concerning the alleged alien mummies. In response, the chair of NASA's UAP study team, David Spergel, responded that if there is any evidence of alien remains, then those in possession of the material should make it publicly available for study.

"When you have unusual things, you want to make data public," Spergel said. "I think of this as like, NASA has one of the most valuable samples from outer space  —  lunar rocks  —  what do we do? We make them available to any scientists who want to work on this. 

"We don't know the nature of those samples that were shown in front of them," Spergel added. "If I was the Mexican government, if I would make a recommendation to the Mexican government — that's not our charge here, we're doing this for NASA — my recommendation [would be]: If you have something strange, make samples available to the world scientific community and we'll see what's there."

Dan Evans, assistant deputy associate administrator for research at NASA's Science Mission Directorate, chimed in to add that the entire point of NASA's UAP study team is to dispel the type of sensationalism and pseudoscience displayed for Mexican lawmakers this week. 

"I'll just add one of the main goals of what we're trying to do here today, is to move conjecture and conspiracy towards science and sanity," Evans said. "And you do that with data, as David says, and that's the whole purpose of this study."

As it turns out, Maussan has a history of wheeling out fake alien remains. Micah Hanks, Editor of The Debrief and a longtime UAP researcher, says that Maussan's latest alien body hoax is "unfortunately not the first time this sort of thing has happened." 

In 2015, Maussan organized an event in Mexico City marking the release of a blurry photograph depicting what appeared to be the remains of a small mummified humanoid alien. "However, once clear copies of the image were circulated online just hours after their unveiling at the event, it was quickly determined that the image actually depicted historic remains belonging to an indigenous American child which, decades ago, had been displayed for a time in a museum," Hanks told Space.com "Some of the individuals involved at the time issued public apologies on account of the child's remains being misrepresented in such a way."

It remains unclear what these most recent "alien mummies" might be, but an analysis of their physiology posted to social media suggests they have been assembled from parts of various mammals such as llamas. 

As Reuters reported, some of the other alleged alien corpses Maussan has presented over the years have turned out to be cobbled together from the remains of mummified children.

Was this space horror game meant to evoke found footage style? Or to be a dark commentary on politics in rural America? Or to bring in the "so bad that it's good" feelings common in the space horror genre?

I found myself figuratively (and literally) stumbling in the dark to find the plot of The Greyhill Incident, which I really wanted to love because it's an indie game and space horror — the perfect combo for me.

But somewhere in the game's opening minutes, I began to lose interest in the characters real fast. "Dad, we need to get out of this cursed place, I hate this neighborhood hole," says a preteen glaring at the 1990s-era television with poor signal. As if overcome by his confusing statement he just lay there, listlessly, as dad rambled something about not believing the government.

Eventually, I (in control of "Dad") got to go outside in search of ... something interfering with the TV. After I whacked Dad drearily against trees, trailers, anything but my objective in the cloistering dark, eventually I found my way and a blurry image emerged of a silver alien craft landing in a nearby field. Now, I thought, the story will get going. Sadly it only got worse from there.

Related: Best space horror games

Refugium Games describes the plot of 'The Greyhill Incident' as "a story-driven survival-horror game about an classic alien invasion [that] takes place during the early 90s." 

The early 90s is indeed an interesting setting for conspiracy-driven stories; without getting into details on this family-friendly site, there were a few unfortunate incidents involving survivalists that (like our characters here) had very negative opinions about the U.S. government.

I thought it would be interesting to see what aliens would add to that historical backdrop, but the conspiracists and extraterrestrials alike were forgettable in both shape and in character. Without spoiling too much of the plot, suffice it to say the aliens not only don't look scary, they also aren't too hard to kill. There's also a strange lack of motive to their actions, which perhaps is the point?

Other self-imposed limitations made the game very hard to navigate. Extremely dark settings and not infrequent graphic aberrations made it hard for me to make sense of anything. While I did watch The X-Files in the 1990s with poor TV reception (as my family didn't have cable) and am used to vague alien settings, the plot didn't make up for the things I was unable to see.

I do want to put in a word in favor for Refugium Games, however, because they're a small, indie developer and so many other big websites have had negative reviews about their new game. 

The team certainly worked hard on this, and after playing the game through, I honestly think with more development time to improve the plot pacing, voice recording, and bit of a graphics touch up would have moved the game to a decent game (at the least) instead of the mess that we currently have. And that may be already ongoing.

The developers have made changes in response to some of the early complaints that made gameplay even more difficult, including improvements to stealth, stamina and the flashlight. So stay tuned, and check in periodically — my review may be happily out of date down the road, but for now, I'd give this one a miss.

The Greyhill Incident is available now on Steam, PS5, and Xbox Series X/S.

Ever since U.S. astronomer Edwin Hubble discovered that our galaxy is just one among many galaxies about a century ago, researchers have wondered how special (or not) the Milky Way is in the universe, said study co-lead author Jianhui Lian, of the Max Planck Institute for Astronomy in Heidelberg, Germany.

"Finding ways to compare our home galaxy with more distant galaxies is what we need if we want to know whether the Milky Way is special or not," Lian said in a statement.

Related: The Milky Way galaxy may be a different shape than we thought

The fact that Earth dwells within the Milky Way means scientists know more about it than any other galaxy. For instance, the Milky Way is currently the only spiral galaxy in which astronomers can analyze large numbers of individual stars in terms of their locations, chemistry, temperature and other properties. Measuring how the levels of various chemicals have changed over the course of its history can in turn shed light on how the Milky Way and other galaxies may have grown and evolved over time.

However, until now, scientists had not analyzed how all these chemicals in the Milky Way might look from a distance. Doing so is key to comparing the Milky Way to other galaxies that astronomers have examined from afar.

"To the best of my knowledge, this idea of the 'alien's' view of the Milky Way is rather new," study co-lead author Maria Bergemann, an astrophysicist also at the Max Planck Institute for Astronomy, told Space.com. "I find it cool and out-of-the-box."

In the new study, the researchers depended on progress made in the past decade or so to analyze the Milky Way in a systematic manner. For example, the European Space Agency's Gaia spacecraft has tracked the brightnesses, motions and distances of nearly 1.5 billion stars in the Milky Way.

In addition, there is now much more and much better data for distant galaxies, making it easier to compare the Milky Way to them. For instance, the MaNGA survey analyzed nearly 10,000 galaxies in depth across 2,700 square degrees of the sky. (In comparison, the full moon as seen from Earth covers about 0.5 square degrees.)

The MaNGA survey examined how each galaxy's chemical composition varies from its center to its outer regions. Furthermore, modern simulations of galaxy formation and evolution can model the history of thousands of galaxies after the Big Bang to the present day. For instance, the TNG50 simulation from scientists in Germany and the United States models a cube of space that is more than 230 million light-years across, tracing the simultaneous evolution of thousands of galaxies across 13.8 billion years of cosmic history.

In the new study, the researchers set out to reconstruct what alien astronomers would see if they were to analyze the Milky Way to map the abundance of what astronomers call "metals" — all elements heavier than the hydrogen and helium that make 99% of all "normal" matter in the universe. (Mysterious dark matter is about six times more common than normal matter, however.)

Related: What is a spiral galaxy?

The Milky Way is shaped like a disk, so the scientists focused on how alien scientists would see the abundance of metals vary within the galaxy. As stars grow, the process of nuclear fusion that helps keep stars alive produces metals within the stars, and when massive stars die in supernova explosions, they expel those metals outward. As such, stars born earlier in time contain fewer metals, whereas later-born stars hold more. Mapping out which regions of a galaxy have stars with fewer metals or more reveals which regions formed its stars earlier and later.

The astronomers also had to account for how interstellar dust can smudge the view of the Milky Way from Earth. This involved combining their observations with known properties of dust and stars to reconstruct the real distribution of stars in the galaxy.

The scientists found that if they tracked the average metal content of stars from the Milky Way's core outward, it increased, reaching a metal content close to that of our sun at a distance of about 23,000 light-years from the center. (The sun lies about 26,000 light-years from the heart of the galaxy.) 

However, at greater distances from the Milky Way's core, the average metal content drops, reaching about one-third of the sun's value about 50,000 light-years from the galaxy's center.

To find out why this belt of metallicity exists, the researchers looked at stars based on their age group. They found that each age group followed a trend where there was greater metal content close to the Milky Way's core and less metal further out. However, older stars with much lower metal content are more abundant near the heart of the galaxy, while younger stars are more frequent farther out. Averaged out, this led to the pattern of metallicity the scientists detected.

The astronomers then compared the Milky Way with 321 galaxies in the MaNGA survey with masses similar to our galaxy that also feature similar amounts of stars. These galaxies are all also visible face-on, helping the researchers see how metal levels vary across each galaxy. The scientists used these same criteria to identify 134 Milky-Way-like galaxies in the TNG50 simulation.

All in all, the astronomers found that the Milky Way is not common but not unique among galaxies. Only about 1% of the galaxies in the MaNGA sample and 11% of the galaxies in the TNG50 simulation displayed a similar pattern of metals to the Milky Way. They noted that this discrepancy between 1 and 11% may be due to uncertainties in the MaNGA data and limitations of the TNG50 simulation's accuracy in modeling the universe.

In addition, the team found that the chemical nature of the Milky Way is rare among galaxies of its rough shape and structure.

"The main implication is that our Milky Way is not a typical Milky-Way-like galaxy," Bergemann said. "In other words, the Milky Way may have evolved differently, compared to others like it."

When it comes to why the Milky Way appears unusual, the scientists noted that the relative scarcity of metal-rich stars near our galaxy's center might be related to the formation of the so-called bulge, an approximately spherical region of older stars surrounding the galactic center out to a distance of about 5,000 light-years. The birth of the bulge likely depleted most of the hydrogen gas in the area, making later star formation much more difficult. 

But its also possible, the researchers said, that our galaxy's central supermassive black hole may have at some point become unusually active, spewing out particles and radiation that inhibited star formation.

Team members added that the relative scarcity of metals in the Milky Way's outer disk could also be explained by a number of different scenarios. For instance, our galaxy might have swallowed a smaller galaxy with gas that contained very few metals. This gas may have later served as the raw material for stars with fewer metals in the Milky Way's outer disk. The estimates that astronomers currently have for the extent of the Milky Way's outer disk may also be off, skewing how different the Milky Way appears compared with other galaxies.

In the new study, the researchers focused on iron, since this metal is relatively easy to measure in stars in the Milky Way.

"An interesting research direction would be to try measuring more chemical elements," Bergemann said. "For example, oxygen, a key element for life on Earth, can also be measured in other galaxies, and we will soon get a lot of data for the chemical evolution of oxygen in the Milky Way — for example from 4MOST [at the Paranal Observatory in Chile.] Another potentially crucial element is carbon."

The scientists detailed their findings online June 22 in the journal Nature Astronomy.

A new search for extraterrestrial life aims to find out by listening for radio pulses from the center of our galaxy. Narrow-frequency pulses are naturally emitted by stars called pulsars, but they're also used deliberately by humans in technology such as radar. Because these pulses stand out against the background radio noise of space, they're an effective way of communicating across long distances — and an appealing target to listen for when searching for alien civilizations. 

Scientists described the alien-hunting strategy in a new study, published May 30 in The Astronomical Journal. Researchers led by Cornell University graduate student Akshay Suresh developed software to detect these repetitive frequency patterns and tested it on known pulsars to be sure it could pick up the narrow frequencies. These frequency ranges are very small, at about a tenth of the width of frequencies used by a typical FM radio station. The researchers then searched data from the Green Bank Telescope in West Virginia using the method. 

Related: Are aliens real?

"Until now, radio SETI has primarily dedicated its efforts to the search for continuous signals," study coauthor Vishal Gajjar of the SETI Institute, a nonprofit organization dedicated to the search for intelligent life in the universe, said in a statement. "Our study sheds light on the remarkable energy efficiency of a train of pulses as a means of interstellar communication across vast distances. Notably, this study marks the first-ever comprehensive endeavor to conduct in-depth searches for these signals."

The researchers are listening in to the middle of the Milky Way because it is dense with stars and potentially habitable exoplanets. What's more, if intelligent aliens at the core of the Milky Way wanted to reach out to the rest of the galaxy, they could send signals sweeping across a wide array of planets, given their privileged position at the center of the galaxy. Using narrow bandwidths and repeated patterns would be a prime way for aliens to reveal themselves, as such a combination is extremely unlikely to occur naturally, study co-author Steve Croft, a project scientist with the Breakthrough Listen program, said in a separate statement. 

The method uses an algorithm that can search through 1.5 million telescope data samples in 30 minutes. Though researchers did not find any telltale signs in their first search, they say that the speed of the algorithm will help improve searches in the future.  

"Breakthrough Listen captures huge volumes of data, and Akshay’s technique provides a new method to help us search that haystack for needles that could provide tantalizing evidence of advanced extraterrestrial life forms," Croft said. 

Following the success of Aliens: Dark Descent’s top-down tactics and Aliens: Fireteam Elite, fans of the Alien IP can look forward to even more xenomorph-y goodness. All-new projects are in active development across several studios, including a VR game titled Alien: Rogue Incursion. Disney, the new owner of the IP, as well as other Fox assets, is very much interested in keeping the xenos alive and spitting acid.

Mind you, the Predator franchise, first entangled with Alien in Dark Horse’s 1990 Alien vs. Predator comic series, isn’t getting nearly as much attention when it comes to video games. That’s even despite the decent success of Predator: Hunting Grounds (2020) and the huge hit that was Prey (2022), the Predator prequel we had always hoped for

For more sci-fi horror, we recommend checking out our up-to-date list of the best space horror games. We also have some thoughts about the rankings of the Alien and Predator movie series, as well as why and how Disney should reboot Alien vs. Predator.

Now, let’s go deep into the hive and show those bugs what flamethrowers and pulse rifles can do. Get tactical, marines!

10. Alien Resurrection

• Platforms: PS1
• Developer: Argonaut Games

We wouldn’t see another major Alien FPS until 2000’s Alien Resurrection, which, you guessed it, was intended to release alongside the 1997 movie of the same name. So, what’s up with that massive gap? Well, development didn’t go smoothly, and the game was stuck in development hell for quite a while before finally releasing in late 2000.

Somehow, it wasn’t hammered too hard by reviewers when it finally released. In fact, the years have been kind to one of the best-looking shooters on PS1. More specifically, the oppressive atmosphere is top-notch, and there are several playable characters spread throughout the story, each with their own weapons and special equipment.

9. Aliens vs. Predator: Extinction

• Platforms: Xbox, PS2
• Developer: Zono

The 2000s also led to an off-beat mix of real-time strategy and the Aliens vs. Predator IP. Developed by Zono, who already had experience with the genre, AvP: Extinction represents perhaps the weirdest big-budget release the Alien has ever been used for. It was a risk worth taking as there’s nothing out there quite like this game.

The focus was put on unit management and combat over base-building and the gathering of resources. Also, the entire game revolves around three campaigns which are light on actual storytelling, but shape each level and the starting conditions depending on the narrative. Each species plays very differently, so AvP: Extinction almost feels like three weird real-time strategy titles bundled into one.

A warning for those curious: it’s tough as nails.

8. Aliens: Infestation

• Platforms: Nintendo DS
• Developer: WayForward Technologies, Gearbox Software

The Alien franchise had been transformed into 2D sidescrollers before, but, nonetheless, it was strange to see a new one launch in 2011 and only for the Nintendo DS. The tie-in veterans at WayForward teamed up with Gearbox to craft a Metroid-like take on the IP, with a heavy focus on exploration and the “permadeath” of the colonial marines that the player controls. It’s “game over, man, game over” if the entire party is wiped out.

Like many other Alien games, Infestation’s story deals with the aftermath of Aliens and Alien 3, with a heavy focus on the U.S.S. Sulaco, which is adrift in space. To capture the movies’ slasher vibes, the developers created 20 unique characters to make sure their (more than likely) deaths resulted in gut-punches to the players.

Anyone into 2D action games with an emphasis on non-linear exploration should give this one a try. The sprite work is exquisite too which is a nice bonus for those who enjoy retro gaming.

7. Aliens: Fireteam Elite

• Platforms: PC, Xbox One/Series X/S, PS4/5, Nintendo Switch
• Developer: Cold Iron Studios

We already mentioned Aliens: Fireteam Elite in the intro, and we hadn’t forgotten about it. Mind you, it’s a game that could’ve used some extra polish and a bigger budget, but it’s got its heart where it matters. After the colossal disappointment that was Aliens: Colonial Marines (2013), Fireteam Elite felt like the co-op game we were promised around a decade ago. More surprisingly, many elements from Prometheus made it into the post-Aliens narrative, a creative choice that separates it from other Alien titles centered on the United States Colonial Marine Corps.

The character classes feel robust, and there are strong progression and customization systems in place to make Aliens and/or co-op shooter fanatics want to stick around past a single playthrough – that is no small feat when it comes to these games! With the addition of cross-play and solid post-launch content (both free and paid), Fireteam Elite is the go-to Aliens shooter at the moment.

6. Aliens vs. Predator (2010)

• Platforms: PC, Xbox 360, PS3
• Developer: Rebellion

AvP shooters had another shot at glory in 2010, and with Rebellion back developing the reboot of sorts. The full story is told across three different campaigns, following in the footsteps of Monolith’s AvP 2 instead of their 1999 game. As for the multiplayer, the offering of modes (both competitive and co-op) was pretty big, but the game struggled to find a sizable audience.

The most interesting thing about AvP 2010 is that Rebellion took some big swings with gameplay elements, such as melee combat, giving it a special flavor and a really visceral feeling in the moment-to-moment gameplay. Some shots missed their mark though, and the campaigns were a bit short, but it squarely delivered on the promise of more carnage between science fiction’s most famous horror icons. It also looks great to this day when maxed out on PC.

5. Aliens: Dark Descent

• Platforms: PC, Xbox One/Series X/S, PS4/5
• Developer: Tindalos Interactive

Shortly after Fireteam Elite reinvigorated the Alien video games scene, along came Aliens: Dark Descent from publisher Focus Entertainment. With a very different take on the source material, this time players can experience a real-time tactics game from a top-down perspective. While it’s definitely harder to get into than the rest of the games in this list, it’s quickly become one of our favorite approaches to the sci-fi franchise.

Long story short: Dark Descent has perfectly executed the feeling of being in command of a squad of colonial marines venturing into xenomorph-infested territory. The narrative hook is solid, and the progression systems that surround the nail-biting missions feel fresh in surprising ways. Command-based tactics and combat might not be everyone's cup of tea, but fans of the movie Aliens who are looking for a different type of game will find plenty to love here.

4. Aliens vs. Predator Classic 2000

• Platforms: PC, macOS
• Developers: Rebellion

1994 also saw the release of a strong Alien vs. Predator FPS on the Atari Jaguar, but it wasn’t until 1999 that Rebellion had a chance to truly wow players. Technology had come a long way in just a few years, and the full-3D graphics powered the ultimate Alien and Predator power fantasies, as well as super-tense human marine gameplay.

In early 2010, after several years of (legal) unavailability, AvP was re-released under the title Aliens vs. Predator Classic 2000. This version works on modern computers and has controller support as well as many other improvements. Moreover, it packs all the extra content released back in the day (and online multiplayer).

The storylines for each species are independent of one another and take players through original locations as well as iconic scenarios from the Alien movies. If you can grapple with the aged controls and old-school level design, this one shouldn’t be missed.

3. Alien vs. Predator (arcade)

• Platforms: Arcade
• Developers: Capcom

Though Alien vs. Predator games had already landed on Nintendo systems, the first big splash for the crossover IP was Capcom’s AvP arcade beat ‘em up. It’s considered to be one of the best games ever made within that genre, and we’re inclined to agree. It still looks gorgeous and packs quite a punch, with tight controls and level variety that aren’t all that common for that type of action game.

There are four characters available (the game can do three-player co-op): the Predator warrior and hunter, Major Dutch Schaefer (based on Arnold Schwarzenegger’s character from the original Predator movie), and Lt. Linn Kurosawa, a human cyborg expert in martial arts. They all work together to put an end to an alien infestation that has overrun a major city in futuristic California. It’s a breezy, wild ride which takes the best elements from the movies and comics released before 1994, and 100% a must-play – you’ll have to turn to emulation though.

2. Aliens vs. Predator 2

• Platforms: PC, macOS
• Developer: Monolith Productions

Although Monolith’s 2001 sequel to Rebellion’s classic hasn’t received a remaster nor a modern re-release, it remains the best Alien vs. Predator game ever. That might include being one of the best Alien games as well – the colonial marine campaign in particular is absolutely spectacular.

The jump in graphical fidelity was vast, and each of the three campaigns – interwoven this time around – feels meaty and challenging. More importantly, each species had a bigger arsenal of weapons and abilities to destroy their enemies and move around the levels. It all culminated with an excellent online multiplayer that some communities are still keeping alive to this day.

1. Alien: Isolation

• Platforms: PC, macOS, iOS, Linux, Android, PS3/4, Xbox 360/One, Nintendo Switch
• Developer: Creative Assembly

Of course, this list wouldn’t be complete without Alien: Isolation, the first-person horror game that dared to capture the magic of Ridley Scott’s original masterpiece. It truly felt (and still feels) like lightning in a bottle, and the fact it was developed by a studio with no prior experience with first-person titles made it even more anomalous.

Taking cues from indie horror hits from the early 2010s, such as Amnesia (2011), Creative Assembly was able to inject back some genuine horror and tension into an IP which had focused for far too long on action-heavy scenarios and colonial marines. The story takes places 15 years after the events of the first movie, following Ellen Ripley’s daughter, Amanda, as she investigates the disappearance of her mother aboard a space station that’s reliving the xenomorph terror.

Isolation isn’t just the best Alien game ever, but also one of the strongest installments of the franchise as a whole. It’s available on almost every modern platform, so there’s no excuse to skip it.

But for aliens in other solar systems, our doomsday scenario may be their everyday — and life might get along just fine. In a new study, astronomers propose that extraterrestrial life could exist in so-called terminator zones, the border between light and dark halves of an exoplanet.

"These planets have a permanent day side and a permanent night side," Ana Lobo, an astrophysicist at University of California, Irvine (UCI) and lead author of the new work, said in a statement. "This is a planet where the dayside can be scorching hot, well beyond habitability, and the night side is going to be freezing, potentially covered in ice. You could have large glaciers on the night side."

Related: What really makes a planet habitable? Our assumptions may be wrong

This seemingly strange kind of planet is actually quite common, particularly around the dim small M dwarf stars that make up nearly 70% of all stars in our galaxy, the Milky Way. Around these smaller stars, exoplanets often become tidally locked, a gravitational phenomenon in which one side of the planet always faces the star. (Similarly, tidal locking is why Earth only sees one side of the moon.)

Astrobiologists often focus on ocean worlds since water is such a key ingredient for life. Lobo and collaborators, however, wanted to find new niches where life may be able to survive. "We are trying to draw attention to more water-limited planets, which despite not having widespread oceans, could have lakes or other smaller bodies of liquid water, and these climates could actually be very promising," Lobo said.

Through computer simulations, Lobo showed that terminator zones on planets with a significant amount of land — versus those covered entirely in oceans — could, in fact, support liquid water and therefore life. With too much water, however, everything evaporates, covering the surface in a thick cloud of vapor.

A slew of upcoming planet-hunting telescopes could search such terminator zones for signs of life, from the famed James Webb Space Telescope to the future Habitable Worlds Observatory, slated to take to the skies in the 2040s. 

The study was published March 10 in The Astrophysical Journal.

The story was originally published on Live Science.

Follow us on Twitter @Spacedotcom and on Facebook. 

In a draft paper, the pair said it is feasible an extraterrestrial spaceship could be in our galactic neighborhood, exploring the region by the means of "dandelion seeds" — small spacecraft that can gather and send back information, similar to the way humans send out spacecraft to explore planets.

Avi Loeb, an astronomer at Harvard University, and Sean M. Kirkpatrick, director of the Pentagon’s All-domain Anomaly Resolution Office (AARO) — established in July 2022 by the Department of Defense (DoD) to detect and study "objects of interest" — released the draft, Physical Constraints on Unidentified Aerial Phenomena, on March 7. It is not an official Pentagon document but was carried out in partnership with the DoD. It has not been peer-reviewed.

Loeb is known for his research into 'Oumuamua — an interstellar visitor from beyond the solar system. Astronomers first detected the cigar-shaped object in 2017 and originally thought it was a comet. However, its elongated shape, its lack of coma (the cloud of gases that envelope a comet), and the fact that it was accelerating away from the sun raised questions about the comet theory. Loeb suggested instead that 'Oumuamua was an alien spaceship. 

Six months before 'Oumuamua's close approach to Earth, a small interstellar meteor measuring around 3 feet (1 meter) wide smashed into Earth. This meteor, IM2, was not related to 'Oumuamua, but it got Loeb thinking. 

That coincidence inspired him "to consider the possibility that an artificial interstellar object could potentially be a parent craft that releases many small probes during its close passage to Earth, an operational construct not too dissimilar from NASA missions," Loeb told Live Science in an email. "These 'dandelion seeds'... could be separated from the parent craft by the tidal gravitational force of the sun or by a maneuvering capability."

In the draft paper, Loeb and Kirkpatrick looked at Unidentified Anomalous Phenomena (UAPs, the government's preferred term for UFOs) confined by known physics. The authors suggest the dandelion seed probes could reach Earth for exploration without being detected by astronomers as they would likely be too small to reflect enough sunlight for survey telescopes to detect.

"Equipped with a large surface-to-mass ratio of a parachute, technological 'dandelion seeds' could slow down in the Earth's atmosphere to avoid burnup and then pursue their objectives wherever they land," they wrote.

Aliens would likely want to explore rocky planets with an atmosphere in the solar system, the authors propose. From a distance, Venus, Earth and Mars would all look appealing, with Earth being of greatest interest once aliens found signatures of liquid water. The alien civilization that created the probes would not need to be on the mothership. It would be unlikely that it could even communicate with the probes. 

The alien civilization may not even exist anymore. Most stars in the galaxy formed billions of years before the sun. A habitable planet with intelligent life could have been sending out probes long before Earth formed. Searching for "resembles checking our mailbox for any packages that may have accumulated over time there, even if the senders are not alive anymore," Loeb said.

Since first suggesting 'Oumuamua was an alien spaceship, Loeb has faced criticism from the scientific community. One Perspective article published in Nature Astronomy in 2019 said the idea ‘Oumuamua was sent to Earth on purpose was "provocative" and "baseless."

In 2021, a letter published in the journal Astronomy & Astrophysics dismissed the idea on logistical impracticalities of interstellar travel: "Given the likely cosmological timescales required to traverse between stars, we conclude that it is unlikely that 'Oumuamua has been sent by an extraterrestrial civilisation and more likely that it is just an unusually shaped rock, which has happened to wander into the solar system."

Another study, published on March 22, 2023, explains 'Oumuamua's strange movements as the likely result of hydrogen off-gassing — again refuting the alien spacecraft theory. 

Still, the Pentagon has taken a renewed interest in studying unidentified objects over U.S. airspace in the previous year. Since the AARO's founding last summer, the office has opened more than 360 new investigations into alleged UAP encounters reported by U.S. military personnel. About half of these have been explained as "balloons or balloon-like entities," while the other half lack sufficient data to conclusively resolve.

Editor's note: This article was updated on Mar. 27 to correct a typo. A previous version of the story said most stars in the solar system are older than the sun; the text now reads "most stars in the galaxy." The sun is the only star in our solar system.

This article was originally posted on Live Science.

The matter of extra-terrestrial life has fascinated mankind for quite some time now, and the movie industry has made sure over the decades to make some serious profits thanks to the UFO craze. However, the subgenre has also evolved with time, giving birth to refreshing takes on alien invasion movies.

Now, what’s an alien invasion movie? Well, it goes beyond simply featuring alien lifeforms visiting Earth, so that throws stories such as E.T. or Arrival out of the window. The aliens have to be hostile. Okay, what about The Thing? One could argue it’s an alien invasion movie, but at the end of the day, it’s just a deadly organism that crash-landed on Earth long ago.

By limiting ourselves to hostile conflicts with entire alien species that want to take over Earth, we’ve come up with a pretty solid list of the best alien invasion movies (in no particular order, before anyone decide to invade our comments section). 

On the matter of aliens, you might want to check our extensive articles on the entire Alien and Predator movie franchises, and maybe meet some extra-terrestrial lifeforms (good and bad) yourself with the best space exploration games and space horror games. 

1. War of the Worlds (2005)

• Release date: June 29, 2005
• Cast: Tom Cruise, Dakota Fanning, Justin Chatwin, Tim Robbins

Based on H.G. Wells’ 1898 novel, Steven Spielberg’s take on The War of the Worlds is generally regarded as one of the lesser movies in his filmography, yet it managed to crack $600 million worldwide and has gained a solid following over the years thanks to its atypical blockbuster nature.

While we’ve seen several audiovisual reinterpretations of the famous novel over the decades, and most cinephiles would look back to the 1953 movie as the best one out of the bunch, there’s something about Spielberg’s version – maybe it’s the relentless grimness – that makes it incredibly attractive despite its many failings, underwhelming original ending included.

2. Edge of Tomorrow

• Release date: June 6, 2014
• Cast: Tom Cruise, Emily Blunt, Bill Paxton, Noah Taylor

Another Tom Cruise movie made it into our list, and with good reason: Edge of Tomorrow was one of the biggest surprises of 2014 thanks to a tight, action-packed script which masterfully mixed the alien invasion subgenre with time-travel shenanigans.

Based on Hiroshi Sakurazaka’s novel All You Need Is Kill, Edge of Tomorrow presents a near future in which most of Europe is occupied by an unstoppable alien species. Major William Cage (Cruise), a public relations officer, is forced to join an operation against the aliens, only to end up experiencing a time loop that could be the key to defeating the invaders. It’s both exciting and dark, but also a surprisingly funny rollercoaster ride. Don’t skip it.

3. Invasion of the Body Snatchers (1956)

• Release date: February 5, 1956
• Cast: Kevin McCarthy, Dana Wynter, Larry Gates, King Donovan

Here’s another instance of two widely known adaptations of the same book. Most sci-fi aficionados are familiar with the 1978 movie by Philip Kaufman, but going back to the 1956 adaptation – only two years after Jack Finney’s novel came out – is highly recommended.

Don Siegel’s movie remains one of the best political allegories of the 1950s and an excellent sci-fi reflection of North American society and the widespread mindset of those years in the States. Furthermore, it’s still a genuinely scary watch that feels way more focused than its 1978 counterpart.

4. Attack the Block

• Release date: May 11, 2011
• Cast: John Boyega, Jodie Whittaker, Nick Frost, Alex Esmail

Time for some sci-fi comedy! Attack the Block is one of the smaller (if not the smallest) movies on the list and an indie surprise that came from the UK. The story follows a teenage street gang who have to defend themselves – and their neighborhood – from ferocious alien creatures that emerge from meteorites. It’s got some important things to say about the marginalized British youth, and stays fun (and funny) until the credits roll.

While the movie underperformed at the box office, it received a largely positive critical reception and allowed both director Joe Cornish and actor John Boyega (now a Star Wars legend) to make the jump to much bigger movies. A sequel is now in development.

5. Independence Day

• Release date: July 3, 1996
• Cast: Will Smith, Jeff Goldblum, Bill Pullman, Judd Hirsch

Roland Emmerich’s magnum opus (yes, dumb plot points and all) is arguably the biggest alien invasion movie ever. While its 2016 sequel amplified the menace to ridiculous levels, the original flick has a distinct charm linked to its era which can’t be replicated. Moreover, its effective mix of practical and digital effects holds up.

The movie was also at the forefront of the large-scale disaster movie resurgence of the mid-late 1990s. It’s big and loud, adventurous and funny, and worked with a remarkably diverse cast – led by peak Will Smith and Jeff Goldblum – on top of everything. It was a winning combination that completely demolished the global box office of 1996. And that speech by Pullman is just *chefs kiss*.

6. Mars Attacks!

• Release date: December 13, 1996
• Cast: Jack Nicholson, Pierce Brosnan, Danny DeVito, Michael J. Fox

1996 ended with another big alien invasion blockbuster, though this one crashed and burned at the box office and struggled to convince the critics. However, Tim Burton’s zany and utterly deranged take on the subgenre found some love, and B-movie fanatics haven’t forgotten about it (and neither has pop culture).

This one is undoubtedly the wildcard of our list, but we’re fully committed to defending a movie with an unbelievable all-star cast having the time of their lives and embracing self-conscious humor, and filled to the brim with some of the strangest imagery in a Hollywood production ever. It’s hard not to smile when thinking about these invaders from Mars.

7. Signs

• Release date: August 2, 2002
• Cast: Mel Gibson, Joaquin Phoenix, Rory Culkin, Abigail Breslin

M. Night Shyamalan’s The Sixth Sense normally gets most of the attention when people talk about the “golden age” of the divisive director, but Signs remains one of his strongest works. And no, the infamous “water scene” does not ruin it. In fact, rewatching the movie while treating its aliens as literal demons actually works. Try it!

Backed by legendary producers Frank Marshall and Kathleen Kennedy, Signs feels like a homage to Steven Spielberg’s alien-centric movies at times, but Shyamalan took the premise to his own territory, heavily exploring the themes of faith and kinship on a small scale against the backdrop of a truly scary (but unexpectedly quiet) invasion.

8. The World’s End

• Release date: July 19, 2013
• Cast: Simon Pegg, Nick Frost, Paddy Considine, Martin Freeman

The final chapter in Edgar Wright’s Three Flavors Cornetto trilogy embraced the alien invasion subgenre with a unique twist which we won’t spoil here, but its influences are clear (and some of them can be found in this list). Unsurprisingly, it also has many tricks up its sleeve and puts humor above everything else.

The best thing about The World’s End is that it fully commits to its initial “pub crawl” premise even when things start to get a bit too weird, resulting in an off-beat sci-fi comedy that leads to a stupefying resolution and ultimately feels way more mature than the two previous entries of Wright’s iconic anthology.

9. They Live

• Release date: November 4, 1988
• Cast: Roddy Piper, Keith David, Meg Foster, Peter Jason

Hey, we kept The Thing out of this list, but that doesn’t mean we’ve forgotten about master of horror and campy action John Carpenter. Based on the 1963 short story 'Eight O’Clock in the Morning' by Ray Nelson, They Live is an excellent work of science fiction which helps understand much of the cultural and economic climate of the Reagan-era United States.

Of course, like most of Carpenter’s works, They Live also comes together as a paranoid action-horror flick full of cheesy but memorable one-liners and remarkable scenes that have grown more famous in pop culture as the years passed.

10. A Quiet Place 1 & 2

• Release date: April 6, 2018
• Cast: Emily Blunt, John Krasinski, Millicent Simmonds, Noah Jupe

Many would call A Quiet Place and its sequel “monster features”, but the latter made it clear they’re alien invasion movies as well. Born from a spec script by Bryan Woods and Scott Beck which actor-turned-filmmaker John Krasinski later rewrote, A Quiet Place has a simple but strong idea that has been mined twice to great success.

A post-apocalyptic world dominated by blind extra-terrestrial creatures with an acute sense of hearing was more than enough to get audiences on board, but the films’ strength lies in strong family drama and believable characters doing their best in really dire situations with no hope of saving the world on the horizon. No big heroics here, but let’s see where it all goes with the already-announced third instalment and spinoff.

Gravitational waves ripple out when objects with mass move through space. Bigger objects — such as planets, neutron stars or black holes — produce more prominent gravitational waves. These space-time ripples were first directly detected in 2015, but since then, scientists have been getting better at spotting the waves as they lap at our cosmic shores. 

Now, new calculations published Dec. 5 to the preprint database arXiv suggest that the U.S.-based Laser Interferometer Gravitational-Wave Observatory (LIGO) can look beyond conventional sources for these space-time ripples. Colossal alien spacecraft traveling at high speeds, or pushed along by warp drives, would also produce the telltale vibrations, the authors said. 

Related: James Webb Space Telescope could help hunt for habitable alien worlds

The LIGO detector spots gravitational waves from the tiny distortions they make in space-time as they pass through it. Made up of two intersecting L-shaped detectors — each with two 2.48-mile-long (4 kilometers) arms and two identical laser beams inside — the experiment is designed such that if a gravitational wave passes through Earth, the laser light in one arm of the detector will get compressed while the other expands, creating a tiny change in relative path lengths of the beams arriving at the detector. The warpings of space-time that even the largest gravitational waves make, however, are minuscule — often the size of a few thousandths of a proton or neutron — meaning that LIGO is incredibly sensitive and requires strict maintenance and calibration.

To see how far this sensitivity could be stretched, scientists made calculations of the smallest object that would generate clearly detectable gravitational waves on Earth. It turns out, it would still be pretty big: To be detectable by LIGO, an alien mothership would need to weigh roughly the same as Jupiter, travel at one-tenth the speed of light, and be within 326,000 light-years of Earth.

Are spaceships of this scale and speed even possible? The researchers don't know, but they hope to squeeze down the ship size to more reasonable proportions as increasingly sensitive gravitational wave (GW) detectors, such as the European Space Agency's 2037 Laser Interferometer Space Antenna, are deployed. The physicists also noted that advanced alien warp drives would create gravitational wave patterns that would be distinguishable from natural sources and that, if detected, these alien waves could even provide humans with clues about how to reverse engineer the technology.

"This is because the shape of the GW signal is entirely dependent on the trajectory of the object," they wrote in the paper. "Thus, as a burst signal is detected, one can attempt to reason the qualities of the transportation mechanism present based on the shape of the GW signal."

Originally published on LiveScience.

You'll uncover the six fundamental constants that shape the universe and the consequences should they ever change. To reveal the cause of the universal glitches, astrophysicists from around the world also attempt to answer the question, why doesn't the universe make sense?  

Elsewhere in the latest issue, you'll uncover the theory of time before the Big Bang and the events that may have led to the creation of the universe as we know it. Also you'll discover how scientists are probing space rocks to solve the mystery of ultra-hard diamond formation. 

Related: Space roar: The mystery of the loudest sound in the universe

Did you know that the larger a black hole gets, the less dense it becomes? You'll discover how that's possible, along with bewildering black hole physics as All About Space reveals the 50 most amazing facts about black holes. 

The latest issue also includes a Q&A with Dr Florence Raulin-Cerceau, Messaging Extraterrestrial Intelligence's vice president, who says "We've probably been detected by extraterrestrials".  

Within the latest stargazer section you'll also find useful information about what's shining in the night sky and when's the best time to see it. 

A glitch in the universe 

When it comes to the laws of physics, you could be forgiven for thinking there are rules which apply no matter where you are in time or space. After all, this is what we are taught.

But everything you think you know about the universe could be wrong, thanks to a glitch. The laws of physics may be different across the universe, in both space and time. This is according to a theory that has been in testing for over two decades that, if proven correct, could rewrite the laws of physics altogether. 

Read the full feature in the latest All About Space

What happened before the big bang ?

Could there have been a time before the Big Bang? In other words, could the universe have existed before it even began?

May there have even been previous universes? Such ideas, once the preserve of high-concept science fiction and philosophical debates, are gaining a new scientific credibility in the 21st century. Some cosmologists are wondering if the Big Bang was merely an intermediate phase and not the true start of the universe at all. 

Theories such as the ekpyrotic universe, ‘Big Bounce’ models and cyclic cosmology have been around for a while, but data from sensitive space probes could put some of these on a firmer footing. But what exactly was the Big Bang, and why are some scientists now changing their minds about it? 

Read the full feature in the latest All About Space

Mysteries of the universe: Ultra-hard diamonds in the sky  

A group of scientists are getting very excited about these ultra- hard diamonds. After all, they reckon they’ve found evidence of lonsdaleite having formed on a dwarf planet some 4.5 billion years ago, and the resulting study has the potential to be very useful indeed. Scientists have known about lonsdaleite for many years. 

It was first discovered in 1967 in a meteorite called Canyon Diablo, found in an impact crater in the desert of northern Arizona. Duly named after British crystallographer Dame Kathleen Lonsdale, one of the first two women elected a fellow of the Royal Society in 1945, it was soon determined to be a much harder form of diamond. 

Read the full feature in the latest All About Space

That's why, for the first time in 35 years, a team of policy experts and scientists have united to establish a set of alien-contact protocols for the entire world to follow in the event of a sudden encounter with E.T. 

"Science fiction is awash with explorations of the impact on human society following discovery of, and even encounters with, life or intelligence elsewhere," John Elliot, a computer scientist at the University of St. Andrews in Scotland, said in a statement. Elliot is the coordinator of the University of St. Andrews' newly established SETI Detection Hub, the cross-disciplinary organization that will establish the new alien contact protocol. 

Related: 9 Strange, Scientific Excuses for Why Humans Haven't Found Aliens Yet

According to Elliot, the new research group will "go beyond thinking about the impact on humanity" of a potential alien encounter and start focusing on how we should respond instead. 

Currently, the only alien contact protocol that humans have was established by the Search for Extraterrestrial Intelligence Institute (SETI) community in 1989. The protocol, which was last revised more than a decade ago, is vague when it comes to the international response to extraterrestrial communication; it mainly focuses on the importance of sharing discoveries with the public and broader scientific community. In the event of confirmed alien contact, the protocol's main practical tip for scientists is to seek instruction from the United Nations or another governing body. (What the United Nations should do is another open question.)

From finding traces of water on Mars to discovering potentially Earth-like exoplanets, advances in space exploration in recent decades have made the idea of life on other worlds more plausible. Yet despite more than a century of efforts to get in contact with these potential lifeforms, humans have yet to hear back.

Rather than focusing on sending messages to aliens, the new SETI Detection Hub will scan signals for potential messages sent from alien lifeforms and will develop a framework for attaching meaning to those signals. They'll also create impact assessments; deliver reports that outline the implications of specific policies; and develop protocols and treatises for responding to hypothetical alien messengers. 

"Will we ever get a message from E.T.? We don't know. We also don't know when this is going to happen,"" Elliot said. "But we do know that we cannot afford to be ill-prepared — scientifically, socially, and politically rudderless — for an event that could turn into reality as early as tomorrow."

While conspiracy theories about potential alien visitors to Earth have abounded recently, the U.S. Department of Defense filed a report this week claiming there's no evidence of extraterrestrial visitors in more than 140 cases of unidentified aerial phenomena (UAPs) reported by the U.S. military. Foreign spy drones and "airborne clutter," like weather balloons, are the far more common explanations for oddities in America's skies. At least, for now.

Originally published on Live Science.

According to several U.S. Department of Defense (DoD) officials who spoke anonymously to The New York Times last week, many recent sightings of UFOs — or unidentified aerial phenomena (UAPs), as the government prefers to call them — are likely just observations of foreign surveillance operations or airborne clutter, such as weather balloons.

Several UAP incidents have been officially identified as "relatively ordinary" Chinese surveillance drones, the anonymous officials said. China has previously stolen plans for advanced U.S. fighter planes, and is interested in how the U.S. trains its pilots, the DoD officials added.

Related: NASA UFO study team includes former astronaut, scientists and more

Other UAP sightings recorded by military aircraft, which appear to show airborne objects moving in seemingly physics-defying ways, are likely the results of optical illusions. This includes the infamous video known as "GOFAST," which was recorded by a U.S. Navy aircraft and leaked to the media in 2018. (The video, along with two other leaked films of military encounters with UAPs, was eventually declassified by the government.)

While the object in the GOFAST video appears to be zooming over the water at incomprehensible speeds, this is just an optical illusion created by the angle of the recording relative to the water, the DoD officials told The Times. In reality, the object is moving at no more than 30 mph (48 km/h), the officials added.

A classified UAP report delivered to Congress this week by the DoD's intelligence agencies likely includes the findings reported by The Times. The new report adds new details to cases described in a document that officials publicly released in June 2021, describing 144 alleged UAP incidents reported by U.S. government personnel between 2004 and 2021.

The 2021 report acknowledged that, due to a lack of high-quality data, most alleged UAP encounters could not be conclusively explained. However, the report offered several blanket explanations for UAP in general, including "technologies deployed by China, Russia, another nation, or a non-governmental entity," as well as "airborne clutter" such as birds and weather balloons. 

Nowhere in the report were aliens or extraterrestrials mentioned — however, that did not stop alien conspiracy theories from arising, due in part to the government's general lack of transparency about UAP incidents.

Sue Gough, a DoD spokesperson, told The Times that the government was committed to sharing whatever UAP information it could without putting national security at risk. Government officials also tend to refrain from discussing UAP incidents publicly because there is simply not enough data to conclusively explain them, Gough added.

"In many cases, observed phenomena are classified as 'unidentified' simply because sensors were not able to collect enough information to make a positive attribution," Gough told The Times. "We are working to mitigate these shortfalls for the future and to ensure we have sufficient data for our analysis."

As the DoD continues its investigation into UAP sightings, NASA has also launched an independent UAP study team, which will operate from October 2022 to mid-2023. According to NASA, the team will focus on collecting and analyzing as much UAP data as possible, in order to develop new methods for identifying the unidentifiable objects in America's skies.

Originally published on Live Science.

Alien: Earth is upon us — the first TV show set in the Alien universe — and it's absolutely fantastic. The series is a stunning continuation of form for the venerable sci-fi horror franchise after Alien: Romulus got things back on track last year, and a great excuse to watch all the Alien movies again. Check out our How to Watch Alien: Earth guide to see where it's streaming in your country.

Thankfully, it's easy to nail down the order of both the chronological and release order lists, as the Alien movies are very good at letting us know the dates of events. The bigger problem becomes figuring out if they're all canon. You could argue that the Alien vs Predator movies aren't part of the official timeline — especially with the Aliens seemingly being created in Alien: Covenant — but Alien: Earth being set before Covenant seems to confirm the retcon. Short version? David didn't create the aliens; he just cooked up a fresh batch in a lab using the black goo developed by the Engineers.

So where does that leave us? Who knows, but for now we're considering everything canon. If you want to stick to the pure Alien movie timeline, it begins in the year 2089 with Prometheus, when the colonization of distant worlds has already begun, and advances up to the year 2381 with Alien: Resurrection.

Given that Weyland-Yutani is featured in the upcoming Predator: Badlands, though, it's looking very likely that more Alien vs Predator crossovers are on the way. It might be time to watch through all the Predator movies in order, too. Oh noooooooo.

There are no spoilers in this list beyond the basic premise of each movie and some curiosities and references, but if you want to go in as blind as possible, stick to the bullet list below.

Alien movies in chronological order

• Alien vs. Predator
• Aliens vs. Predator: Requiem
• Prometheus
• Alien: Covenant
• Alien: Earth
• Alien
• Alien: Romulus
• Aliens
• Alien 3
• Alien: Resurrection

1. Alien vs. Predator

• Release date: August 13, 2004
• Cast: Sanaa Lathan, Raoul Bova, Lance Henriksen

After a failed AvP project which was developed in the 90s, Shane Salerno’s script set the action in (back then) present day: 2004. An expedition led by Charles Bishop Weyland (Lance Henriksen) wants to investigate a massive heat signal under the ice on Bouvetøya, an island off the coast of Antarctica. What comes afterwards is a chaotic battle between long-dormant Xenomorphs and three Predator hunters, with humans caught in the middle.

As the first Alien vs. Predator crossover movie, AvP tries really hard to connect both franchises, especially with the inclusion of Aliens veteran Lance Henriksen as the founder of Weyland Industries (which later becomes Weyland-Yutani after a merger). However, it put the origins of the Xenomorphs – as presented by Alien (1979) – into question, and Ridley Scott’s prequel movies later trashed the entire idea of Xenos existing this early in the timeline. Furthermore, a major flashback set in the early days of human civilization shows that both species have been going at it for an awfully long time.

2. Aliens vs. Predator: Requiem 

• Release date: December 25, 2007
• Cast: Steven Pasquale, Reiko Aylesworth, John Ortiz

20th Century Fox’s (now Studios) second go at AvP was met with abysmal reviews and a cold shoulder from most fans, although it delivered enough unrestrained nastiness and refreshing in-universe concepts to get diehard fans talking. AvP: Requiem is set in 2004 too, starting right after the previous movie cuts to black. There are notable differences between the theatrical cut and the extended one (which is the way to go), but the main events remain unchanged in the latter.

This movie keeps pushing the idea of everything in both franchises happening in one big timeline, and ends up tying Yutani Corp’s huge space travel advancements we see in the Alien movies to Predator tech. This ain’t canon anymore for the Alien franchise, but as mentioned before, the AvP movies have been embraced by the Predator timeline. As bad as the movie is, the Yutani nod was a cool note to end on.

3. Prometheus

• Release date: June 1, 2012
• Cast: Noomi Rapace, Michael Fassbender, Charlize Theron

The first of the Alien prequels by original director Ridley Scott starts in 2089 (prologue aside), with archaeologists Elizabeth Shaw (Noomi Rapace) and Charlie Holloway (Logan Marshall-Green) discovering an ancient star map on Earth that sends them – backed by the Weyland Corporation – to the distant moon LV-223, where they arrive in December 2093.

While Xenomorphs as we know them don’t show up in this movie, we learned tons about their makers – referred to as Engineers – and their connection to humankind. The sci-fi rules of all the chaos and horror that ensue are confusing to say the least, but Scott and his team made one thing clear: the classic Xenomorph didn’t exist at this point, instantly vaporizing both AvP movies out of the timeline.

In a hilarious move, the upcoming TV series, which Scott is producing and actively working on, appears to be playing the same card and trashing his take on the Xenos’ origin, as it will take place on Earth “in the near future.” Continuity? They don’t know her.

4. Alien: Covenant 

• Release date: May 12, 2017
• Cast: Michael Fassbender, Katherine Waterston, Billy Crudup

Once again, the second Alien prequel kicks off with a distant prologue which teases future events and discoveries. The story itself takes place in the year 2104, 11 years after the Prometheus expedition went missing. The colonization ship Covenant is en route to the planet Origae-6, but a mysterious transmission of a human voice makes the crew look for answers in a nearby planet with Earth-like characteristics.

While Ridley Scott still showed more interest in everything that wasn’t the actual Xenomorph, there’s plenty of classic Alien goodness in Covenant, finally giving the nightmarish creatures a clear origin which, as mentioned before, doesn’t vibe with the AvP flicks. Sadly, the third movie of the trilogy will probably never happen following a disappointing box office haul, and Covenant’s ending is anything but close to leading into the crashed Engineer ship found in the original Alien.

5. Alien Earth

• Release date: August 13, 2025
• Cast: Sydney Chandler, Timothy Olyphant, Alex Lawther, Samuel Blenkin, Essie Davis, and Adarsh Gourav

The first — and so far only — TV show set in the Alien universe, but what a debut on the small screen. When the deep space research vessel USCSS Maginot crash-lands on Earth, a ragtag group of soldiers and survivors must band together to escape the horrors that were on board. This time around, the horrors aren't just limited to the Xenomorph, though, as the Maginot was carrying up a menagerie of extraterrestrial nightmares when it fell to Earth.

The show is set in 2120, making it a prequel to the original Alien and placing it 16 years after Alien: Covenant. Nice and easy to slot into the timeline.

Beyond people getting turned into lunch by cosmic horrors, our heroes will have to contend with the greatest evil our kind has ever known … corporations. Earth is controlled by five megacorps: Prodigy, Weyland-Yutani, Lynch, Dynamic, and Threshold. Prodigy is the star of the show here, having developed a technology that lets it put a human consciousness into robots.

Alien: Earth launched to rave reviews, earning a 93% fresh on Rotten Tomatoes and garnering some intense praise. In our Alien: Earth review, we called it "an intelligent and thought-provoking bloodbath."

6. Alien 

• Release date: May 25, 1979
• Cast: Sigourney Weaver, Tom Skerritt, John Hurt

The events of the original horror masterpiece take place in 2122, which puts only 18 years between it and Covenant. Of course, this being the movie that started it all, everything in Alien stands on its own. There’s a big mystery, plenty of scares and gore, and little more. The worldbuilding is intriguing but slim, and we learn early on that Weyland-Yutani was actively seeking the strange and lethal Xenomorph.

If we accept Scott’s intent and try to work his Alien prequels into the original canon, we have to assume that, at some point in between Covenant and this movie, the company learned about the existence of the Xenomorph and the Engineers, either through a survivor of whatever happened afterwards or via remote transmission. Also, a group of Engineers from another planet or moon – since the synth David (Michael Fassbender) massacred an entire planet before creating the monster – got their hands on plenty of eggs and then crashed on LV-426. If everyone involved wanted to tie things up nicely, these events would’ve been the backbone of the prequel trilogy’s conclusion. But alas…

7. Alien: Romulus

• Release date: August 16, 2024
• Cast: Cailee Spaeny, Isabela Merced, David Jonsson

Alien: Romulus takes place in 2142. Weyland-Yutani got its hands on the dangerous Xenomorphs and ran experiments on them in a space station. Enter the cast of young characters, who board said space station to steal some highly-regulated equipment. Of course, things get ugly fast, but the movie revealed a far more sinister mystery than just Xenomorphs that broke containment.

The story kicks off with a shuttle from Weyland-Yutani retrieving a Xenomorph cocoon from the debris left by the Nostromo’s explosion in the first Alien movie. Yup, the unwanted alien passenger that slaughtered the Nostromo’s crew simply stayed alive, asleep and adrift in outer space until someone found it. Without getting into further plot details, Romulus ends in a way that doesn’t break the basic premise of Aliens, which is that Weyland-Yutani continues to look for Xenomorphs and risks an entire colony years later.

8. Aliens 

• Release date: July 18, 1986
• Cast: Sigourney Weaver, Carrie Henn, Michael Biehn

57 years after the events of Alien, in 2179, the sole survivor of the Nostromo, Ellen Ripley (Sigourney Weaver), is rescued in deep space and debriefed by her employers, who seem skeptical about her claims. To make matters worse, LV-426 is now the site of a large terraforming colony. And of course, some poor employees eventually come across the massive derelict ship full of dormant Xenomorph eggs.

Though there are some obvious ellipses happening early on, the entire story plays out during the year 2179, which suggests that Ripley is brought to a Weyland-Yutani station close nearby after she’s rescued, and that LV-426 isn’t too far away either. And it all makes sense, since the Nostromo never got too far from the planetoid in the first movie before Ripley destroyed it and went for a long nap inside the shuttle Narcissus, which just drifted away for more than half a century.

9. Alien 3 

• Release date: May 22, 1992
• Cast: Sigourney Weaver, Charles S. Dutton, Charles Dance

Alien 3 begins shortly after Ripley, Newt (Carrie Henn), Hicks (Michael Biehn), and the damaged android Bishop (Lance Henriksen) enter cryonic stasis. In one of the darkest movie starts of all time, Ripley crash-lands and finds herself trapped in a claustrophobic prison on Fiorina “Fury” 161, a barren world. Of course, the Xenomorphs had something to do with that, and the nightmare follows her down to the hellish planet.

The entire movie takes place in 2179, which means the post-Aliens nap was extremely short and that everything in David Fincher’s off-beat and smaller threequel happens rather fast. A major question mark that still causes heated debate among fans is the appearance of Bishop’s creator (both played by Lance Henriksen), who doesn’t seem too bothered by some grave injuries he sustains in the climax. Was he the real Michael Weyland or just a more elaborate synth designed to fool her into giving up the Xenomorph?

10. Alien: Resurrection 

• Release date: November 12, 1997
• Cast: Sigourney Weaver, Winona Ryder, Ron Perlman

Alien: Resurrection made the biggest time jump in the franchise, distancing itself from Weyland-Yutani and that entire storyline. It’s set in the year 2381, 202 years after the death of Ellen Ripley and the last known Xenomorph. One would think the franchise would take advantage of the situation to swap Sigourney Weaver’s character for a new lead, but nope – she’s cloned, alongside the embryo of a Xenomorph Queen, using blood samples taken before her death by Jonathan Clemens (Charles Dance).

The entire premise (and development) of Joss Whedon’s script was quite the ride, and French director Jean-Pierre Jeunet’s sensibilities only made Resurrection even weirder, but it’s nonetheless a fascinating look into a far future of the Alien universe which somehow feels even more depressing and dire than the classic Weyland-Yutani era.

Alien movies in release order

• Alien (1979)
• Aliens (1986)
• Alien 3 (1992)
• Alien: Resurrection (1997)
• Alien vs. Predator (2004)
• Aliens vs. Predator: Requiem (2007)
• Prometheus (2012)
• Alien: Covenant (2017)
• Alien: Romulus (2024)
• Alien: Earth (2025)

Our guide to the best space books includes investigations into the wonder of our galaxy and beyond. You'll also find deep dives into physics and astronomy as well as accounts from astronauts about life in space. Others are more grounded, telling the stories of the people who helped launch space programs with their feet firmly placed on Earth.

But these aren't all non-fiction books for education purposes: We've also included our favorite science fiction books that offer a different perspective of space. No matter what type of space book you're after, we're confident you'll find something to suit in our selection.

If you're looking for something more specific, take a look at our guide to the best astrophysics books or the best space photography books. And if you're shopping for kids, our guide to the best space books for pre-teens might come in handy.

The quick list

The best space books to read in 2025

Books about NASA and space exploration

The books in this section all deal with human stories of real space missions, the realities of living and working in space, and the people on the ground making space missions come to life.

Some books (Dr Space Junk vs The Universe) take a more broader look at humans in space, and the impact we have, and others (See You in Orbit?) take a look at what the future of space travel might hold.

Jump to a specific space exploration title using the links below:

• A Portrait of The Scientist as a Young Woman by Lindy Elkins-Tanton
• Space Forces: A Critical History of Life in Outer Space by Fred Scharmen
• Back to Earth by Nicole Stott
• Beyond by Stephen Walker
• See You in Orbit? by Alan Ladwig
• Dr Space Junk vs The Universe by Alice Gorman
• Apollo's Legacy by Roger D. Launius

A Portrait of the Scientist as a Young Woman

Lindy Elkins-Tanton of Arizona State University is the principal investigator of NASA's Psyche mission, a mission designed to explore an asteroid known as (16) Psyche. But since it's three times further from the Earth than the sun and it's made primarily of metal, it's no easy feat.

In A Portrait of the Scientist as a Young Woman, Elkins-Tatton discusses the ins-and-outs of the Psyche mission, the intriguing path she took to get her position, and how the mission went.

The book covers everything from her experience conducting field research in Siberia to her work supporting healthy culture in the ivory tower. Being only the the second woman ever to be awarded a major NASA space exploration contract, her point of view is an interesting one indeed.

You can find out more about the book and the author in our interview with Lindy Elkins-Tanton.

Space Forces

Like plenty of kids, Fred Scharmen was fascinated by the depictions he saw of what life in space might look like. But Scharmen grew up to be an architect and urban designer, which taught him to see all the silent assumptions, fears and hopes that were hidden in those images.

In Space Forces: A Critical History of Life in Outer Space, Scharmen examines seven different visions of life in space, exploring the cultural beliefs they betray and asking us to think more critically about why we want to go to space and how to translate our values into exploration. Mixing together reality and science fiction, this is a very interesting but dense read that might be very different from what you're expecting.

To learn more about the author and Space Forces, read our interview with Fred Scharmen. We have also published an excerpt from Space Forces to give you a taste of what to expect from the book.

Back to Earth

Retired NASA astronaut Nicole Stott is one less than 600 people to have reached space, and she hopes the stories of that experience will inspire readers to take a planetary perspective on their daily lives.

In Back to Earth: What Life in Space Taught Me About Our Home Planet ― And Our Mission to Protect It, she offers new philosophies for living on Earth informed by her experience in orbit and melds her experiences in space with stories of people on Earth who act on the same value she sees as so crucial to spaceflight.

If you want to find out more about Back to Earth, you can read our interview with the author, Nicole Stott. We also have an excerpt from Back to Earth that you can read to get a taste of what to expect from the book.

See You in Orbit?

Alan Ladwig is a former manager at NASA and in See You In Orbit? Our Dream of Spaceflight, he dives into the history and future of space flight.

Ladwig provides an in-depth history into space travel, dating all the way back to the theoretical ideas from the 1920s and 1930s, and moving through the decades to the present day, with the likes of Blue Origin, SpaceX, Virgin Galactic and more taking aim at private and commercial space travel.

This is a very comprehensive and in-depth read, and if you're any interest in space travel at all, it makes for essential reading. Ladwig's writing is both accessible and entertaining, with many humorous anecdotes sprinkled through, along with Ladwig drawing upon his own experiences during his time at NASA.

To find out more about Ladwig and See You in Orbit?, we'd recommend that you read Space.com's interview with the author.

Dr. Space Junk vs the Universe

What happens to satellites when they die, and come to think of it, when do they die? Those are just some of the questions that Alice Gorman wants to answer in her book Dr Space Junk vs The Universe: Archaeology and the Future.

Alice Gorman is an Australian archaeologist who studies objects related to spaceflight, and what we can learn by thinking about space through the lens of archaeology. Dr Space Junk vs The Universe is an engaging story of the ways being human shapes how we go to space.

From Aboriginal songs tucked on the Voyagers' Golden Records to the importance of the size of a spacecraft, Gorman offers a new perspective on the history — and future — of space.

You can find out more about Dr Space Junk vs The Universe in our Q&A with Gorman, which covered the book as well as Gorman's experiences with the archaeology of space.

Beyond

On April 12, 1961, Russian cosmonaut Yuri Gagarin became the first person to leave Earth's orbit and travel into space, marking a significant milestone in the space race between the United States and the Soviet Union.

In Beyond: The Astonishing Story of the First Human to Leave Our Planet and Journey into Space, author and documentary filmmaker Stephen Walker recounts intimate details of the months, and years, leading up to Gagarin’s historic flight, revealing the true stories of the Soviet space program as the agency prepared to launch the first human into space — only weeks before American astronaut Alan Shepard's suborbital flight on May 5, 1961.

Walker also discusses the historical impact of Gagarin's flight and how it set the stage for NASA's Apollo program.

Apollo's Legacy

How do we understand a transformative event like the Apollo missions to the moon? Many present it as proof of American ingenuity and success, but there's much more to the story.

In Apollo's Legacy: Perspectives on the Moon Landings by space historian Roger D. Launius, he probes the impacts Apollo had technologically, scientifically and politically, as well as analyzing what we can draw from it to understand the country's modern space program.

The book is written as a scholarly text, but it's accessible to anybody with an interest in space history and the circumstances that spawned Apollo.

If you want to know more about Apollo's Legacy: Perspectives on the Moon Landings and its author, read our Q&A with Roger D. Launius.

Science and physics books

The books in this section delve into astrophysics and other scientific angles about our universe and space at large.

Some books here tell the story of a specific person and their impact on the world of astrophysics (The Girl Who Named Pluto) while others delve deeper into the laws of physics (Einstein's Unfinished Revolution) or provides a rich overview of everything that makes our galaxy what it is (The Milky Way).

You can find a bigger list of similar books in our guide to the best astrophysics books.

Jump to a specific book using the list below:

• The Milky Way by Moiya McTier
• Horizons: The Global Origins of Modern Science by James Poskett
• The Disordered Cosmos by Chanda Prescod-Weinstein
• For Small Creatures Such As We by Sasha Sagan
• Einstein's Unfinished Revolution by Lee Smolin
• Finding Our Place in the Universe by Helénè Courtois
• The Girl Who Named Pluto by Alice B. MicGinty

Finding Our Place in the Universe

In Finding Our Place in the Universe, French astrophysicist Helénè Courtois describes the invigorating quest to discover the Milky Way's home. In 2014 Courtois was part of a research team that discovered the galactic supercluster which contains the Milky Way, which they named Laniakea. This means "immeasurable heaven" in Hawaiian.

In this engaging and fast-paced book, Courtois describes her own journey in astrophysics and highlights the key contributions of numerous female astrophysicists. The reader is right there with her as Courtois travels to the world's leading observatories in pursuit of Laniakea, and it's easy to see why the challenge of discovering our galaxy's home became so seductive.

Readers who want them will learn all the scientific and technical details needed to understand the discovery of Laniakea, but it's also possible to enjoy this book as a pure tale of adventure.

To find out more about the book and the author, read our Q&A with Courtois about her hunt for Laniakea.

The Milky Way

Astronomers have written the Milky Way's story many times over; scientists have traced violent collisions in its past and future and peered into the supermassive black hole lurking at its heart. But if our galaxy could tell us its story, what would it say?

Astrophysicist and folklorist Moiya McTier tells that story in her delightful book, The Milky Way: An Autobiography of Our Galaxy. McTier's Milky Way makes for a prickly narrator as the book zips through everything from the formation of the universe through the ways scientists think it might come to an end.

This isn't the most in-depth, rich scientific text, but if you're fairly new to learning about our galaxy, it makes for great reading.

To learn more about The Milky Way, read our interview with Moiya McTier. We've also previously published an excerpt from The Milky Way if you want a taste of what to expect.

Horizons

What if everything we're taught about the history of astronomy and physics is wrong? That's what Horizons: The Global Origins of Modern Science posits to its reader.

In this book, James Poskett, a historian of science and technology, focuses on how science has always been a global endeavor and how that story was overshadowed by a biased Westernized version.

Astronomy and physics play key roles in the story he tells, with cameos from key figures such as Ptolemy and Isaac Newton, although the book spans several scientific fields, including natural history and evolution as well.

To find out more about Horizons: The Global Origins of Modern Science, read our interview with author James Poskett.

For Small Creatures Such As We

Author Sasha Sagan is the daughter of Cosmos co-writer Ann Druyan and famed astronomer Carl Sagan. Before you know anything else about this book, then, that should give you something of an idea of what to expect.

Sasha Sagan describes her book, For Small Creatures Such as We: Rituals for Finding Meaning in Our Unlikely World, as a love letter to her parents. But rather than dealing solely with science, it dives into the secular side of spirituality.

Upon starting a family of her own, Sagan wanted to have rituals and traditions that would bond them together. But being non-religious, she re-evaluated what these traditions could be and this book explores how rituals like holidays can be inspired by the "magic" of nature, space and science rather than religion.

To find out more about For Small Creatures Such as We, read Space.com's interview with the author.

The Girl Who Named Pluto

How did an 11-year-old English schoolgirl come to name Pluto? In The Girl Who Named Pluto: The Story of Venetia Burney, Alice B. McGinty recounts one child's history-making turn on a fateful morning in 1930. Although the book is aimed at kids aged between 4 to 8, there's plenty for older children to connect with as well. And the vintage-flavored illustrations by Elizabeth Haidle make the experience a visual delight.

Venetia had connected her love of mythology with her knowledge of science to christen the new planet after the Roman god of the underworld, refusing to let her age or gender to hold her back.

McGinley says she hopes Venetia's tale inspires her readers — girls, in particular. "I hope girls read it and feel empowered to be part of the scientific process," she said. "I hope boys read it and feel empowered, too, and understand how important girls are to science."

To find out more about The Girl Who Named Pluto, read Space.com's interview with the author, Alice B. McGinty.

The Disordered Cosmos

Theoretical physics is supposed to be about pure, crisp ideas. But physics is done by humans, and human society brings messiness to any endeavor. That reality means every aspect of physics is marked by the social constraints of who is allowed to do physics in harmony with their identity and who is not.

Chanda Prescod-Weinstein, a theoretical physicist at the University of New Hampshire, tackles the implications of that reality in her thought-provoking book, The Disordered Cosmos: A Journey into Dark Matter, Spacetime, and Dreams Deferred.

This deals with much more than just astrophysics, with Prescod-Weinstein dealing with the physics of just about everything. She also delves into issues relating to racism and sexism that affect the scientific medium, making this an interesting and thought-provoking read in many ways.

To learn more about The Disordered Cosmos, read our interview with the author.

Einstein's Unfinished Revolution

Although many believe that the quantum-mechanics revolution of the 1920s is settled science, Lee Smolin wants to disrupt that assumption.

Smolin, a theoretical physicist based at the Perimeter Institute in Toronto, argues that quantum mechanics is incomplete. The standard quantum model only allows us to know the position or trajectory of a subatomic particle — not both at the same time. Smolin has spent his career looking to "complete" quantum physics in a way that allows us to know both pieces of information.

Smolin's very engaging book, Einstein's Unfinished Revolution: The Search for What Lies Beyond the Quantum offers this unique perspective honed through four decades at the forefront of theoretical physics. ~Marcus Banks

Read a Q&A with Smolin about the new book and the state of quantum physics.

Books about UFOs and the search for life

This section of our favorite space books deals with UFOs and the search for life. We've chosen books that tackle the subject from a scientific point of view. Sarah Stewart Johnson's book takes us to Mars on an in-depth search for life, while They Are Already Here delves into the UFOs that have made the headlines.

Jump to a specific book about UFOs and space exploration using the links below:

• The Sirens of Mars by Sarah Stewart Johnson
• Identified Flying Objects by Dr. Michael P. Masters
• They are Already Here by Sarah Scoles

The Sirens of Mars

More than just a hunt for signs of life, The Sirens of Mars: Searching for Life on Another World is a love letter to the red planet. Author Sarah Stewart Johnson has been obsessed with Mars from a young age, and this book is both a look at the research she's carried out looking for life, and her lifelong obsession with the planet.

A planetary scientist, Stewart Johnson's book is the human story of the search for life on Mars. She shares a host of hidden moments about scientists' views of the Red Planet throughout the pages, and she also delves into how scientists have found and lost hope in the process of studying our nearest neighbor.

This is a surprisingly personal account, and a fascinating read throughout. It's filled with empathetic and evocative language, and it's very accessible to all readers even if you don't have a rich scientific background.

They Are Already Here

Do you remember reading a New York Times story in 2017 that claimed to unveil a Pentagon program dedicated to investigating UFOs? Did you hear rumors about why the FBI closed a solar observatory the next year for then-undisclosed reasons? Are you confused about why there seem to be so many documentaries about alien sightings?

They Are Already Here: UFO Culture and Why We See Saucers, written by freelance journalist Sarah Scoles, tackles these questions and many more. Rather than delve into the investigations themselves, the book deals with the culture around UFO sightings, digging into where encounters come from and the emotional effects such a sighting can have on a person.

If you want to find out more about They Are Already Here: UFO Culture and Why We See Saucers read Space.com's interview with the author. We also have an excerpt from the book if you want a greater idea of what to expect.

Identified Flying Objects

Unidentified flying objects (UFOs) have captured the public's attention over the decades. Rather than aliens, could those piloting UFOs be us — our future progeny that have mastered the landscape of time and space?

Perhaps those reports of people coming into contact with strange beings represent our distant human descendants, returning from the future to study us in their own evolutionary past.

That's the theory that Dr. Michael P Masters goes with in his self-published book, Identified Flying Objects: A Multidisciplinary Scientific Approach to the UFO Phenomenon. The idea of us being them has been advanced before, but this woek takes a fresh look at this prospect, offering some thought-provoking proposals.

If you want more information about the book, read our review of Identified Flying Objects.

Science fiction books

We're moving away from science and theory in our guide to the best space books now. This section focuses on our favorite sci-fi stories. These books draw on science to create new worlds, alternate timelines and thrilling situations for you to lose yourself in.

These books are sometimes scary, sometimes tense, but always engaging. Use the links below to jump to a specific sci-fi title featured in our guide.

• The Apollo Murders by Chris Hadfield
• The Relentless Moon by Mary Robinette Kowal
• The Andromeda Evolution by Daniel H. Wilson
• Delta-V by Daniel Suarez

The Apollo Murders

Not only is Canadian Chris Hadfield an astronaut, he's also a New York Times bestselling author, YouTube star, international speaker, and popular Twitter personality. It's a lot of bows under his belt, but in his first dive into fiction, he proves he can do just about anything he sets his mind to.

The Apollo Murders is a rousing adventure placed amid the tense days of the U.S.-Soviet Union space race in the 1970s following America's lunar landings.

The alternative history is set in 1973 when NASA launches a final top-secret mission to investigate a crewed Soviet space station called Almaz. The clandestine flight continues to the moon as both Russian and American crews target a huge bounty hidden on the lunar surface.

To find out more about the book, read our article where Chris Hadfield talks about writing the The Apollo Murders. We also have an excerpt from The Apollo Murders to give you a taste of what to expect.

The Relentless Moon

Mary Robinette Kowal's Lady Astronaut series imagines what would have happened if Apollo-era spaceflight had continued at the same pace, pushed forward by the existential threat of meteor-caused climate change.

This third book in the series, Relentless Moon, follows astronaut Nicole Wargin on an investigation of threats to a lunar base, exploring how life on the ground continues amid ambitious space exploration. It's a thrilling read that speaks both of an Earth on the brink of destruction and a colonized Moon.

Being the third entry in the Lady Astronaut series, however, you might want to pick up the other two first: The Calculating Stars and The Fated Sky.

The Andromeda Evolution

The Andromeda Evolution from Daniel H. Wilson is actually a sequel to Michael Crichton's 1969 classic novel, The Andromeda Strain. Picking up some 50 years later, it continues to develop the terrifying world that Crichton lays out with immense and thrilling detail.

The story of The Andromeda Evolution deal with otherworldly matter that threatens the future of the Earth. A team of experts come together to investigate what becomes literally a life or death situation: if they can't reach the quarantine zone and enter the anomaly, life as we know it will end.

This is a thrilling read for start to finish, but you'll get much more out of it if you read Crichton's original novel, The Andromeda Strain first.

To find out more about the book, read our in-depth The Andromeda Evolution review, where we also interview author Daniel Wilson.

Delta-V

In Delta-V by Daniel Suarez, an unpredictable billionaire recruits an adventurous cave diver to join the first-ever effort to mine an asteroid.

The crew's target is asteroid Ryugu, which Japan's Hayabusa2 spacecraft has really been exploring since June 2018. From the use of actual trajectories in space and scientific accuracy, to the title itself, Delta-V — the engineering term for exactly how much energy is expended performing a maneuver or reaching a target — Suarez pulls true-to-life details into describing the exciting and perilous mission.

The reward for successful asteroid mining is incredible, but the cost could be devastating.

To find out more about Delta-V, read our Q&A with the author.

More great space books to read

While our guide here includes a range of the best space books generally, we've also got several other lists all narrowing down into specific categories or catering for specific audiences. Browse those lists using the links below.

• Astrophysics
• Space photography
• Space books for kids
• Astronomy
• Spaceflight and space history
• Science fiction
• Space books for preteens

How we test

We typically don't publish full reviews of the space books we read and love, but everything on this list comes highly recommended from our staff, all of whom are space experts and enthusiasts.

We choose books for a number of reasons: Perhaps they give us a new glimpse into life working for NASA or living in space, or maybe they provide an in-depth understanding to the galaxies beyond our own. We've chosen books that suit all age ranges too, and in many cases we've spoken to the authors to get a better understanding of the work that's gone in to writing and compiling each of these entries.

Follow us on Twitter @Spacedotcom and on Facebook.

Chris Impey, University Distinguished Professor of Astronomy, University of Arizona
Daniel Apai, Professor of Astronomy and Planetary Sciences, University of Arizona

The ingredients for life are spread throughout the universe. While Earth is the only known place in the universe with life, detecting life beyond Earth is a major goal of modern astronomy and planetary science.

We are two scientists who study exoplanets and astrobiology. Thanks in large part to next-generation telescopes like the James Webb Space Telescope, researchers like us will soon be able to measure the chemical makeup of atmospheres of planets around other stars. The hope is that one or more of these planets will have a chemical signature of life.

Habitable exoplanets

Life might exist in the solar system where there is liquid water — like the subsurface aquifers on Mars or in the oceans of Jupiter's moon Europa. However, searching for life in these places is incredibly difficult, as they are hard to reach and detecting life would require sending a probe to return physical samples.

Many astronomers believe there's a good chance that life exists on planets orbiting other stars, and it's possible that's where life will first be found.

Theoretical calculations suggest that there are around 300 million potentially habitable planets in the Milky Way galaxy alone and several habitable Earth-size planets within only 30 light-years of Earth — essentially humanity's galactic neighbors. So far, astronomers have discovered over 5,000 exoplanets, including hundreds of potentially habitable ones, using indirect methods that measure how a planet affects its nearby star. These measurements can give astronomers information on the mass and size of an exoplanet, but not much else.

Looking for biosignatures

To detect life on a distant planet, astrobiologists will study starlight that has interacted with a planet’s surface or atmosphere. If the atmosphere or surface was transformed by life, the light may carry a clue, called a "biosignature."

For the first half of its existence, Earth sported an atmosphere without oxygen, even though it hosted simple, single-celled life. Earth's biosignature was very faint during this early era. That changed abruptly 2.4 billion years ago when a new family of algae evolved. The algae used a process of photosynthesis that produces free oxygen — oxygen that isn't chemically bonded to any other element. From that time on, Earth's oxygen-filled atmosphere has left a strong and easily detectable biosignature on light that passes through it.

When light bounces off the surface of a material or passes through a gas, certain wavelengths of the light are more likely to remain trapped in the gas or material's surface than others. This selective trapping of wavelengths of light is why objects are different colors. Leaves are green because chlorophyll is particularly good at absorbing light in the red and blue wavelengths. As light hits a leaf, the red and blue wavelengths are absorbed, leaving mostly green light to bounce back into your eyes.

The pattern of missing light is determined by the specific composition of the material the light interacts with. Because of this, astronomers can learn something about the composition of an exoplanet's atmosphere or surface by, in essence, measuring the specific color of light that comes from a planet.

This method can be used to recognize the presence of certain atmospheric gases that are associated with life — such as oxygen or methane — because these gasses leave very specific signatures in light. It could also be used to detect peculiar colors on the surface of a planet. On Earth, for example, the chlorophyll and other pigments plants and algae use for photosynthesis capture specific wavelengths of light. These pigments produce characteristic colors that can be detected by using a sensitive infrared camera. If you were to see this color reflecting off the surface of a distant planet, it would potentially signify the presence of chlorophyll.

Telescopes in space and on Earth

It takes an incredibly powerful telescope to detect these subtle changes to the light coming from a potentially habitable exoplanet. For now, the only telescope capable of such a feat is the new James Webb Space Telescope. As it began science operations in July 2022, James Webb took a reading of the spectrum of the gas giant exoplanet WASP-96b. The spectrum showed the presence of water and clouds, but a planet as large and hot as WASP-96b is unlikely to host life.

However, this early data shows that James Webb is capable of detecting faint chemical signatures in light coming from exoplanets. In the coming months, Webb is set to turn its mirrors toward TRAPPIST-1e, a potentially habitable Earth-sized planet a mere 39 light-years from Earth.

Webb can look for biosignatures by studying planets as they pass in front of their host stars and capturing starlight that filters through the planet's atmosphere. But Webb was not designed to search for life, so the telescope is only able to scrutinize a few of the nearest potentially habitable worlds. It also can only detect changes to atmospheric levels of carbon dioxide, methane and water vapor. While certain combinations of these gasses may suggest life, Webb is not able to detect the presence of unbonded oxygen, which is the strongest signal for life.

Leading concepts for future, even more powerful, space telescopes include plans to block the bright light of a planet’s host star to reveal starlight reflected back from the planet. This idea is similar to using your hand to block sunlight to better see something in the distance. Future space telescopes could use small, internal masks or large, external, umbrella-like spacecraft to do this. Once the starlight is blocked, it becomes much easier to study light bouncing off a planet.

There are also three enormous, ground-based telescopes currently under construction that will be able to search for biosignatures: the Giant Magellen Telescope, the Thirty Meter Telescope and the European Extremely Large Telescope. Each is far more powerful than existing telescopes on Earth, and despite the handicap of Earth's atmosphere distorting starlight, these telescopes might be able to probe the atmospheres of the closest worlds for oxygen.

Is it biology or geology?

Even using the most powerful telescopes of the coming decades, astrobiologists will only be able to detect strong biosignatures produced by worlds that have been completely transformed by life.

Unfortunately, most gases released by terrestrial life can also be produced by nonbiological processes — cows and volcanoes both release methane. Photosynthesis produces oxygen, but sunlight does, too, when it splits water molecules into oxygen and hydrogen. There is a good chance astronomers will detect some false positives when looking for distant life. To help rule out false positives, astronomers will need to understand a planet of interest well enough to understand whether its geologic or atmospheric processes could mimic a biosignature.

The next generation of exoplanet studies has the potential to pass the bar of the extraordinary evidence needed to prove the existence of life. The first data release from the James Webb Space Telescope gives us a sense of the exciting progress that’s coming soon.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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The intent is to move the scientific understanding of UAP forward, said Thomas Zurbuchen, NASA's associate administrator for science.

"NASA believes that the tools of scientific discovery are powerful and apply here also," Zurbuchen said in a statement. "We have access to a broad range of observations of Earth from space – and that is the lifeblood of scientific inquiry. We have the tools and team who can help us improve our understanding of the unknown. That's the very definition of what science is. That's what we do."

The UAP study team will be led by astrophysicist David Spergel, previously the chair of the astrophysics department at Princeton University. 

"Given the paucity of observations, our first task is simply to gather the most robust set of data that we can," Spergel said in the NASA statement. "We will be identifying what data — from civilians, government, non-profits, companies — exists, what else we should try to collect and how to best analyze it."

Space.com reached out to a number of UAP and UFO (unidentified flying object) groups and leading experts in the field to get their thoughts on NASA's new endeavor.

Related: 2022 could be a turning point in the study of UFOs

Scientific rigor and transparency

NASA should be congratulated for its willingness to investigate UAP, said Robert Powell, executive board member of the Scientific Coalition for UAP Studies.

"During their press conference, it was clear that they would provide an exemplary approach to the subject by combining scientific rigor, transparency and a fundamental curiosity about this longstanding mystery," Powell said. "All scientists interested in the study of these phenomena should welcome NASA's entry into the arena as an indication that the time has come for the scientific community to openly examine this subject, and it is hoped that Congress will appropriate funding to open the study of this enigma to all of academia."

Powell said that the Scientific Coalition for UAP Studies would urge NASA to tap into the background knowledge that has already been obtained by other science organizations and become familiar with "the pitfalls and successes in the study of this subject." This will enable more rapid scrutiny of UAP development areas that need expanded scientific involvement, he said. 

"In order to facilitate a rapid acquirement of known data, the new NASA UAP group should consider identifying an individual that can coordinate data and information sharing with established UAP organizations," Powell said. "This will help avoid duplication of efforts."

Win-win development

Also welcoming NASA's new study is Avi Loeb, head of Harvard's Galileo Project, a systematic scientific search for evidence of extraterrestrial technological artifacts.

The Galileo Project is currently assembling its first telescope system on the roof of the Harvard College Observatory, planning an expedition to retrieve fragments from the first known interstellar meteor, studying satellite data on UAP and designing a space mission to rendezvous with the next anomalous ('Oumuamua-like) interstellar object that zooms into our solar system.

Loeb recently summarized his thoughts about the NASA announcement in an essay titled "Imitation Is the Sincerest Form of Flattery."

Overall, this outcome is gratifying and represents a "win-win" development, Loeb said. "The Galileo Project is now likely to receive a boost to its funding from wealthy individuals and foundations with which I am in close contact," he wrote in the essay. "But most importantly, the Project's scientific mission narrative is now echoed within the government. It does not matter who tells the truth as long as it is being told."

Related: UFO watch: 8 times the government looked for flying saucers

Fishing expedition

Loeb said that it's wonderful that NASA will be engaged in trying to unravel the mysterious nature of UAP. He tags this quest as a "fishing expedition," one that will end up with a mixed bag of natural and human-made objects. 

"But even if we have high-quality data on just a single object that demonstrates something else, such as an extraterrestrial technological origin, it would represent the most important discovery in human history," Loeb told The Jerusalem Post recently.

Loeb said he would be delighted to provide any input that could help NASA's study, "because it shares the intellectual DNA of the Galileo Project," he wrote in the essay. "Government agencies and academia should be working together towards the collection of new evidence-based knowledge on UAP."

Open mindedness applies also to scientific research, Loeb said. "We should explore the unknown by seeking evidence agnostically and not assuming what we might find. Gladly, we now know that both the Galileo Project and NASA agree on following this principle."

Right start

"NASA's new UAP initiative is very encouraging, perhaps even more so than the formation of the Airborne Object Identification and Management Synchronization Group in the Pentagon," said Mark Rodeghier, the scientific director of the Center for UFO Studies in Chicago.

UAP are best investigated openly, Rodeghier said, "both because this will allow a range of qualified researchers to be involved, but also because this will permit the results of the investigation to be shared with the public." 

The military has advanced sensor capabilities, and that may be crucial for gathering critical data on the phenomenon, said Rodeghier. "But I have concern that findings will, as a matter of course, not be shared with the public. Those of us who have been advocating for years that more resources be devoted to studying UAP have always recommended that this be done openly and transparently."

Rodeghier said that, at this stage, NASA is conducting reconnaissance to learn what data are available and how best to study the phenomenon — which is exactly the right start — and he is not concerned about coordination with the military. 

"Down the road, there could be potential for overlap and redundancy in the two efforts, but science is normally best done with multiple research groups working on the same problem, and UAPs are no different," Rodeghier told Space.com. "I do hope that NASA reaches out to the serious UFO community, because we can advise them on data and data-quality issues that we understand from long experience. Our involvement will make their study more robust and comprehensive."

Related: US military taking 'all hands on deck' approach to understanding UFOs

Sharing information

"I think it's great that NASA, the U.S. Navy, and other organizations are starting to take the UFO question seriously. However, I find it strange that the U.S. Air Force, which has been openly investigating this phenomenon since the 1940s, is completely quiet on the issue in modern times," said Michael Masters, a professor of biological anthropology at Montana Technological University. 

In his new book, "The Extratempestrial Model" (Full Circle Press, 2022), Masters makes the case that UFOs and aliens are our future human descendants, coming back through time to visit and study their own evolutionary past.

Masters spotlights a number of case studies of close encounters. It seems that whenever a case involved military personnel specifically, he said, the Air Force Office of Special Investigations was all over it. "Why are they so quiet now? Why aren't these offices talking to each other and sharing information and data they've collected across multiple decades?"

Stigma has lifted

"I think NASA's involvement is extremely significant," said investigative journalist Leslie Kean, author of The New York Times bestseller "UFOs: Generals, Pilots and Government Officials Go on the Record" (Harmony Books, 2010).

"We have to remember that when Jimmy Carter was president, he asked NASA to conduct just the sort of assessment that the agency is undertaking now. NASA said no to the president of the United States.  Now, NASA has initiated data gathering on its own. Clearly the stigma has lifted. We are living in a different world with respect to UAP," Kean said.

At this stage, NASA's task is simply to gather data, Kean said — to find out what data researchers have, what more they should collect and then determine how to analyze it. 

"So we may not be given any major revelations in the near term," she added. "However, this is clearly the first step. And what's really important is that they are looking for data from civilians as well as from government. They will not be working with classified data and will make everything transparent to the public. This should stimulate additional scientific investigation, and it will greatly help lift the stigma even further within the scientific community."

NASA's UAP look-see should help groups like the Galileo Project, and hopefully data can be shared between those two organizations, said Kean. "I hope NASA accesses data from space. If we can document the existence of UAP in space, then we really have something."

Energy, experience and expertise

Kevin Knuth is an associate professor of physics at the University at Albany (State University of New York). He is an active UAP researcher.

"Given that pilots have been, and still are, reluctant to come forward regarding encounters with unidentified aerial phenomena, one must seriously ask whether NASA astronauts have seen significant unidentified phenomena in space," Knuth said. "I would hope that the NASA UAP investigation interviews NASA astronauts to determine what may have been witnessed in space. Perhaps there will also be interviews of former or current cosmonauts?"

Given that civilian organizations are becoming more active in space, there is the potential for a new safety issue involving UAPs, said Knuth. "Does NASA plan to require astronauts to report encounters with unknown objects in space like the U.S. Navy now does?"

Knuth points out that there are a number of former and current NASA scientists actively working to study UAPs via several research groups, including Loeb's Galileo Project. "I would hope that the NASA study team takes advantage of their energy, experience and expertise on the topic," Knuth said.

Anecdotal reports, blurry photos, no solid data

Not everyone is enthusiastic about the NASA UAP effort.

"NASA says that they are establishing an independent group of investigators to look into UAP reports, but it's difficult to see why this is expected to accomplish anything," said Robert Sheaffer, a leading skeptical investigator of UFOs.

For 75 years there have been plenty of people looking into UFO/UAP claims, some of them very educated, and still no solid findings have emerged, Sheaffer said. "So what does NASA bring to the table that wasn't there before? Do people really think that no astronomers or physicists have ever investigated UFO reports until now?"

Sheaffer pointed out that NASA's budget for its UAP appraisal is a modest $100,000, "which in the overheated world of government contracts won't even pay for a single full-time researcher for one year."

By contrast, from 2008 to 2011, the Pentagon's Advanced Aerospace Weapon System Applications Program gave $22 million to the Nevada-based company Bigelow Aerospace Advanced Space Studies to investigate UAPs and their allegedly "collocating" weirdnesses, Sheaffer said. 

"It ended up with reports of poltergeists, paranormal wolf-like creatures and malevolent blue orbs attacking people, but they still learned nothing about the nature of UAPs," he said. "The Department of Defense refused to appropriate any money after that."

Sheaffer senses that the problem is not that there is too much data to analyze; rather, there are only anecdotal reports, blurry photos and other shaky information. 

"Those who are familiar with the history of 75 years of UFO reports understand the perils of taking eyewitness reports at face value, a lesson that government investigators of high strangeness apparently have yet to learn," Sheaffer said.

Leonard David is author of the book "Moon Rush: The New Space Race," published by National Geographic in May 2019. A longtime writer for Space.com, David has been reporting on the space industry for more than five decades. Follow us on Twitter @Spacedotcom or on Facebook.  

This article was originally published at The Conversation. The publication contributed the article to Space.com's Expert Voices: Op-Ed & Insights.

Danny C. Price, Senior research fellow, Curtin University

"Extraordinary claims require extraordinary evidence."
— Carl Sagan ("Cosmos," 1980)

This phrase is the standard that astronomers will be applying to a curious signal captured with China's "Sky Eye" telescope that might be a transmission from alien technology.

An article reporting the signal was posted on the website of China's state-backed Science and Technology Daily newspaper, but was later removed. So have astronomers finally found evidence of intelligent found life beyond Earth? And is it being hushed up?

We should be intrigued, but not too excited (yet). An interesting signal has to go through a lot of tests to check whether it truly carries the signature of extraterrestrial technology or is just the result of an unexpected source of terrestrial interference.

And as for the deletion: media releases are normally timed for simultaneous release with peer-reviewed results — which are not yet available — so it was likely just released a bit early by mistake.

An eye on the sky

Sky Eye, which is offically known as the Five-hundred-meter Aperture Spherical Telescope (FAST), is the the largest and most sensitive single-dish radio telescope in the world. A engineering marvel, its gargantuan structure is built inside a natural basin in the mountains of Guizhou, China.

The telescope is so huge it can't be physically tilted, but it can be pointed in a direction by thousands of actuators that deform the telescope's reflective surface. By deforming the surface, the location of the telescope's focal point changes, and the telescope can look at a different part of the sky.

FAST detects radiation at radio wavelengths (up to 10 cm) and is used for astronomical research in a wide range of areas. One area is the search for extraterrestrial intelligence, or SETI.

SETI observations are mainly done in "piggy-back" mode, which means they are taken while the telescope is also running its primary science programs. In this way, large swaths of the sky can be scanned for signs of alien technology — or "technosignatures" — without getting in the way of other science operations. For special targets like nearby exoplanets, dedicated SETI observations are still carried out.

The hunt for alien technology

Technosignature searches have been ongoing since the 1960s, when the American astronomer Frank Drake pointed the 26-metre Tatel telescope toward two nearby sun-like stars and scanned them for signs of technology.

Over the years, technosignature searches have become far more rigorous and sensitive. The systems in place at FAST are also able to process billions of times more of the radio spectrum than Drake's experiment.

Despite these advances, we haven't yet found any evidence of life beyond Earth.

FAST sifts through enormous amounts of data. The telescope feeds 38 billion samples a second into a cluster of high-performance computers, which then produces exquisitely detailed charts of incoming radio signals. These charts are then searched for signals that look like technosignatures.

With such a large collecting area, FAST can pick up incredibly faint signals. It is about 20 times more sensitive than Australia's Murriyang telescope at the Parkes Radio Observatory. FAST could easily detect a transmitter on a nearby exoplanet with a similar output power to radar systems we have here on Earth.

The trouble with sensitivity

The trouble with being so sensitive is that you can uncover radio interference that would otherwise be too faint to detect. We SETI researchers have had this problem before.

Last year, using Murriyang, we detected an extremely interesting signal we called BLC1.

However, it turned out to be very strange interference (not aliens). To uncover its true nature, we had to develop a new verification framework.

With BLC1, it took about a year from when it was initially reported to when peer-reviewed analysis was published. Similarly, we may need to wait a while for the FAST signal to be analysed in depth.

Professor Zhang Tongjie, chief scientist for the China Extraterrestrial Civilization Research Group, acknowledged this in the Science & Technology Daily report:

"The possibility that the suspicious signal is some kind of radio interference is also very high, and it needs to be further confirmed and ruled out. This may be a long process."

And we may need to get used to a gap between finding candidate signals and verifying them. FAST and other telescopes are likely to find many more signals of interest.

Most of these will turn out to be interference, but some may be new astrophysical phenomena, and some may be bona fide technosignatures.

Stay intrigued

Will FAST's extraordinary signals meet the burden of extraordinary evidence? Until their work is reviewed and published, it's still too early to say, but it’s encouraging that their SETI search algorithms are finding curious signals.

Between FAST, the Breakthrough Listen initiative, and the SETI Institute's COSMIC program, the SETI field is seeing a lot of interest and activity. And it's not just radio waves: searches are also underway using optical and infrared light.

As for right now: stay intrigued, but don't get too excited.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Follow all of the Expert Voices issues and debates — and become part of the discussion — on Facebook and Twitter. The views expressed are those of the author and do not necessarily reflect the views of the publisher.

The news centers on observations by China's "Sky Eye" — the Five-hundred-meter Aperture Spherical radio Telescope (FAST), which is located in southwestern Guizhou province.

One report, by the state-backed Science and Technology Daily, cited Zhang Tonjie, chief scientist of an extraterrestrial civilization search team co-founded by Beijing Normal University, the National Astronomical Observatory of the Chinese Academy of Sciences and the University of California, Berkeley.

Related: The search for alien life

Zhang is reported to have said that the team spotted two sets of intriguing signals in 2020 while sifting through FAST data gathered in 2019. Another signal was apparently picked up this year in data gathered on exoplanet targets. 

However, Zhang reportedly also underscored the possibility that the signals are products of radio interference. Follow-up FAST observations are reportedly on tap. (The Science and Technology Daily story has since been removed from the outlet's site.)

To get some perspective about the FAST rumors, Inside Outer Space reached out to Dan Werthimer, the Marilyn and Watson Alberts SETI (search for extraterrestrial intelligence) Chair in the Astronomy Department and Space Sciences Lab at the University of California, Berkeley. He works with the Beijing Normal University SETI researchers.

Werthimer threw cold water on the possibility that the FAST signals were produced by advanced aliens.

"These signals are from radio interference; they are due to radio pollution from Earthlings, not from ET. The technical term we use is 'RFI' — radio frequency interference. RFI can come from cell phones, TV transmitters, radar, satellites, as well as electronics and computers near the observatory that produce weak radio transmissions," Werthimer said.

"All of the signals detected by SETI researchers so far are made by our own civilization, not another civilization," Werthimer added. "It's getting hard to do SETI observations from the surface of our planet. Radio pollution is getting worse, as more and more transmitters and satellites are built. Some radio bands have become impossible to use for SETI."

Werthimer said that Earthlings might eventually have to go to the far side of the moon to do SETI work.

"A radio telescope on the backside of the moon would be shielded from all of our planet's radio pollution," he said.

Leonard David is author of the book "Moon Rush: The New Space Race," published by National Geographic in May 2019. A longtime writer for Space.com, David has been reporting on the space industry for more than five decades. Follow us on Twitter @Spacedotcom or on Facebook.  

So far no one has found evidence of intelligent aliens elsewhere in the cosmos. But if they do exist, they might be hanging out on Dyson spheres circling the husks of sunlike stars called white dwarfs scattered throughout the Milky Way, a new paper argues.

And that's there we should be focusing our search for extraterrestrials, study co-author Ben Zuckerman, an emeritus professor of physics and astronomy at the University of California Los Angeles, told Live Science in an email.

Based on what that search turns up, astronomers could estimate how many advanced civilizations lurk in the galaxy, he said. 

Related: 4 hostile alien civilizations may lurk in the Milky Way

Long live the civilization

Any advanced civilization needs energy: for food, for transport, for conflict, for comfort and for convenience. Currently, Earth's 7.8 billion people use around 580 million million joules of energy every year, equivalent to the energy output of almost 14,000 million tons of oil, according to The World Counts. Indeed, almost all human energy comes from fossil fuels, as we lack the technological savvy to rely on the largest generator of energy in the solar system: the sun.

If humans covered every square inch of Earth's surface with solar panels, that would generate more than 1,017 joules of energy per second. That would still be losing the majority of energy radiated by the sun, about 1,026 joules per second.

This is the motivation behind Dyson spheres, named for the famed physicist Freeman Dyson, who developed the idea in 1960. If an advanced civilization really wants to harness the awesome energetic output of their home star, they have to build megastructures to capture it, blocking out at least some of the star's light and converting that energy into other useful things. Dyson's original proposal of a solid sphere (with 100% solar coverage) doesn't work because of stability issues, as it would be impossible to keep the star at the center and the entire sphere would disintegrate due to extreme tidal and rotational stresses. Even so, it's easy to imagine an advanced species building rings or swarms of giant solar panel-covered structures to get the job done.

Failed start-ups

But no matter how advanced a species is, and how many Dyson sphere-like objects they build, they will have to contend with the fact that every star has a finite lifetime. If a civilization arose around a typical sunlike star, then someday that star will turn into a red giant and leave behind a cool white dwarf. That process will in turn roast its solar system's inner planets and, as the white dwarf cools off, freeze the outer ones.

So staying put on the surface of a planet is not a viable long-term option. That means any aliens could either pack up and leave, finding a new system to call home, or build a series of habitats that harvest the radiation from the remaining white dwarf.

According to a new paper written by Zuckerman and accepted in May for publication in the journal Monthly Notices of the Royal Astronomical Society, it seems unlikely that an alien civilization would choose to go through the trouble of traveling to a new star just to build a Dyson sphere. Thus, they're only going to build these megastructures around their home stars, which will eventually turn into white dwarfs.

Related: Does every star have planets?

This allows scientists to make a direct connection between stellar lifetimes and the prevalence of Dyson spheres. So, Zuckerman reasoned, if astronomers look for Dyson spheres around white dwarfs and come up empty, that can help estimate how many advanced civilizations may exist in the galaxy. Here’s how the logic works: Astronomers have only measured a small fraction of all the white dwarfs in the galaxy. But if enough aliens decided to build Dyson spheres around their white dwarf homes, then we should see at least one Dyson sphere in our surveys. If we don’t see any at all, then that sets an upper limit on the number of alien  civilizations building Dyson spheres around white dwarfs. Of course there could be aliens who decide not to build Dyson spheres, or aliens that build spheres around other kinds of stars, but Zuckerman argues that over the age of the Milky Way the most likely outcome of advanced civilizations is to build a Dyson sphere around their white dwarf, and so we should focus our searches in that direction.

Taking the long view

However, this search won't be easy. 

"If any Dyson spheres do exist, they will likely be hard to find because there are so many stars that must be searched," Zuckerman noted in an email to Live Science, adding that, "The signal from the Dyson sphere will likely be very faint compared to the star about which it orbits."

Just what is that signal?

The presence of a Dyson sphere (or ring or swarm) around a white dwarf will have two effects. If it's large enough or close enough to the star, it will block the light arriving to Earth just as transiting exoplanets do. But such Dyson spheres might also add a signal from infrared radiation. The megastructures will absorb radiation from the white dwarf and convert that energy into other things. Since no conversion is 100% efficient, this process will leave behind some waste heat that will escape as infrared light.

Surprisingly, we have already found many white dwarfs with excess infrared emission, but that is due to dust in those systems, not megastructures, according to the research paper.

Existing surveys of white dwarfs have found no evidence of any Dyson spheres. Given the total number of white dwarfs that we expect to inhabit the Milky Way, Zuckerman estimates that no more than 3% of habitable planets around sun-like stars give rise to a civilization that chooses to build a Dyson sphere around the resulting white dwarf. However, there are so many planets around sun-like stars that this calculation only provides an upper limit of 9 million potential white dwarf sphere-building civilizations in the Milky Way, the researchers concluded.

In the end, though, nobody knows how many advanced civilizations may live in the Milky Way, if any at all, Zuckerman said. 

"Some astronomers, including me, think that technological life may be a very rare occurrence," Zuckerman said. "Indeed, we might even possess the most advanced technology in our Milky Way galaxy. But no one knows, so it is worth searching for evidence."

Originally published on Live Science.