In an impressive illustration of the enormity of space, NASA recently discovered a space rock roughly the size of Manhattan, just a few months before it was set to fly near Mars.
Up to that point, the behemoth had remained hidden in the inky blackness of space. This was, in part, due to the fact that it came from outside our solar system. Named 3I/ATLAS, it is the third interstellar object ever detected performing a close flyby – after ‘Oumumua in 2017 and 2I/Borisov in 2019.
When ‘Oumuamua was first discovered, Harvard astronomer Avi Loeb famously claimed the cigar-shaped object was likely comprised of alien technology. Now, he has once again made controversial claims regarding 3I/ATLAS.
This interstellar object could be a city-sized alien spacecraft, he posited, and it may have purposefully flown behind the sun to deploy Earth-bound probes when it was out of view from our telescopes.
In an interview with Interesting Engineering, Loeb claimed that “humanity needs a wakeup call” when it comes to researching UAPs and alien life. This can “only stem from high-quality scientific data,” he said. “Once obtained, it will become common practice to fund research on the search for alien technology.”
Other scientists believe Loeb’s methods are counterproductive and even harmful, as they do “not follow the scientific method” and “do not exemplify the process.”
Looking for a ‘confession’ from 3I/ATLAS
3I/ATLAS was first observed as a dot in the night sky by the Asteroid Terrestrial-impact Last Alert System (ATLAS) survey telescope, in Rio Hurtado, Chile. On July 1, it was recorded soaring through space at a speed of 130,000 mph (210,000 km/h). Within 24 hours, 3I/ATLAS was confirmed to be an interstellar object. We know this because it is on a hyperbolic orbital path, meaning it is not gravitationally bound to the sun.
By July 8, Harvard professor Avi Loeb had published a blog post titled ‘Is 3I/ATLAS a Comet or Something Else?’ Since then, he has published a stream of posts on the interstellar space object. These include brief outlines of anomalous characteristics of 3I/ATLAS, as well as a Sept. 25 post claiming that 3I/ATLAS may be even larger than first thought.
In his correspondence with Interesting Engineering, Loeb explained why 3I/ATLAS presents the best opportunity to date to potentially observe extraterrestrial technology up close.
“3I/ATLAS was discovered on July 1, 2025, about four months before its closest approach to the Sun on October 29, 2025,” Loeb explained. “This allows astronomers to monitor its properties in exquisite detail as it gets closer.” This will be aided by the fact that “3I/ATLAS is aligned with the ecliptic plane of the planets around the Sun, allowing the use of space observatories that humans deployed around the Earth and the Solar system planets.”
“When 3I/ATLAS approaches the Sun, its surface will get warmer and its enhanced outgassing will encounter stronger radiation and wind pressures from the Sun,” Loeb continued. “As is well known from interrogation tactics, a high-stress environment elicits confessions. For that reason, 3I/ATLAS might reveal its nature and origin in the coming months.”
Searching for signs of alien technology
The specific “confessions” Loeb is searching for would unequivocally prove that 3I/ATLAS is an alien spacecraft. “A spacecraft could maneuver, emit artificial light or broadcast signals rather than just reflect sunlight,” he told IE. “In addition, a picture is worth a thousand words.”
The reason Loeb believes we may find these signs is due to a list of anomalies he has attributed to 3I/ATLAS. The interstellar object, for example, has a diameter larger than 5 kilometers (3.1 miles). This gives it an incredibly high minimum mass of 33 billion tons – a thousand to a million times higher than that of ‘Oumumua and 2I/Borisov.
3I/ATLAS’s gas plume also showed much more nickel than iron, “as in industrial nickel alloys,” Loeb claims. The light from the object also shows extreme negative polarization, and it temporarily exhibited a forward jet of scattered sunlight during early observations. Curiously, 3I/ATLAS is also aligned to within 9 degrees with the famous unexplained 1977 “Wow! Signal”.
In one of his blog posts, Loeb states: “Dogmatists who insist that 3I/ATLAS is a comet of natural origin must be held accountable to explain all of these anomalies as results of probable natural processes.”
‘Alien of the gaps’
Since he first posited that ‘Oumuamua was an alien spacecraft in 2017, Loeb has faced a great deal of backlash over his claims. In a 2021 interview with IE, the Harvard professor claimed a number of scientists had reached out to him privately, stating they agreed with him. However, they didn’t want to go public as they feared it could damage their reputations and careers.
However, speaking on his StarTalk podcast in August, famous astrophysicist Neil deGrasse Tyson warned against “assuming” that 3I/ATLAS is made of alien technology. He compared this to the theological concept of “God of the gaps” – referring to the fallacy that gaps in scientific knowledge are evidence of God’s existence. In recent times, “‘God of the gaps’ has been supplanted by ‘alien of the gaps,’” deGrasse Tyson argued.
In response, Loeb explained to IE that “Neil is a science popularizer, but not a practicing scientist, as he did not publish a single scientific paper over the past 15 years. I wrote 9 scientific papers on 3I/ATLAS alone over the past two months. Science is guided by evidence, not by popularity contests or beliefs.”
Interestingly, though, Loeb himself has stated that 3I/ATLAS is most likely a natural comet. In his paper titled ‘Is the Interstellar Object 3I/ATLAS Alien Technology?’, he and his co-authors claim that they do not necessarily ascribe to their own “remarkable hypothesis”. Still, it is worth pursuing as “an interesting exercise in its own right.” It is simply “fun to pursue, irrespective of its likely validity.”
3I/ATLAS is ‘obviously a comet’
Other scientists dispute Loeb’s assertion that he is a prolific scientist. Steven Desch, a professor of astrophysics at Arizona State University, calls Loeb’s work “sloppy”.
In an interview with IE, Desch said Loeb “can’t get much accepted through peer review, so he just posts stuff on [preprint server] arXiv constantly. [His papers] are riddled with mathematical errors and gaps in logic. He completely mischaracterizes and misquotes the work of experts.”
Desch goes further, arguing that Loeb “has learned to thrive in our new post-truth attention economy. He claims to raise interest among the public for science, but he does not follow the scientific method, and he does not exemplify the process. [3I/ATLAS is] a comet, it’s always obviously been a comet.”
Martin Rees, a professor of cosmology and astrophysics at the University of Cambridge, UK, concurred, telling IE: “I think we should keep our minds at least ajar to the possibility of alien artifacts. Searches for evidence are surely worthwhile – but I think we should be more sceptical and less credulous than Avi Loeb seems to be!”
3I/ATLAS: A ‘really cool comet’
Desch specifically addressed some of Loeb’s 3I/ATLAS ‘anomalies’ in his interview with IE. “It’s got a lot of carbon dioxide relative to water, compared to solar system comets, but these are exactly the sorts of gases we expect,” he explained. “It has dust. It emitted nickel vapor (something we only learned 5 years ago that comets normally do), and while iron vapor wasn’t seen at first, it was predicted to show up as the comet got warmer. And now it has emitted iron vapor.”
“This object has not done a single non-cometary thing,” Desch continued. “It was pretty much completely understood within days, and any questioning of this long ago ceased to be scientific. It’s a comet, it’s always obviously been a comet. There are so many other things we don’t understand, but this isn’t one of them. It’s a comet. It’s a really interesting comet from another star, it’s the coolest comet we’ve ever seen, but for those in the back: It’s. A. Comet.”
Desch is part of a growing group of scientists who worry about the impact of Loeb’s claims. “What the public needs are the skills to critically sift through evidence and sometimes conclude, yeah, thousands of experts probably have it right,” Desch said. “Instead, he feeds conspiracy theorists convinced that everyone’s hiding something and only the prophets like him, meting out the truth, can be trusted. That is not what the world needs now.”
Gleaning real insight from our interstellar visitors
Some argue Loeb has drawn attention away from truly remarkable discoveries related to 2I/Borisov and 3I/ATLAS. Ironically, they are relevant to the search for alien life beyond our solar system.
“What we’ve learned from Borisov and ATLAS is that objects very similar to comets in our own solar system must be very common in other solar systems,” Desch noted. “They seem to have formed ‘dirty snowball’ bodies just like our solar system did. If you think the circumstances of our solar system are necessary for life, then good news: they are pretty common.”
‘Oumuamua, meanwhile, was likely a chunk of nitrogen (N2) ice, just like we see on the surface of Pluto. “That is consistent with all the observations, and nothing else is,” Desch added. “This implies that other solar systems have their own plutos, and that these must be common.”
Does humanity ‘need a wake-up call’?
Still, Loeb argues that considering the possibility of alien technological beings visiting Earth is a necessary thought experiment.
In his recent paper questioning whether 3I/ATLAS is a technological object, the Harvard professor states that “the consequences, should [his] hypothesis turn out to be correct, could potentially be dire for humanity, and would possibly require defensive measures to be undertaken.” The cosmologist also highlights recent eye-witness testimony and footage of UAPs in his blog posts.
The idea that the third interstellar visitor observed near Earth is a spacecraft is definitely more eye-catching than the Occam’s razor theory. Analyzing it as such might also constitute a fun thought experiment. However, the focus should be on the real scientific discoveries made after these incredibly rare objects fly through our cosmic neighborhood.