As the US prepares to send astronauts back to the moon, a CIA file has resurfaced that claims to have found life there more than 25 years ago. In the 1970s and 80s, the CIA conducted experiments with individuals who claimed they could perceive information about distant objects, events, or people, a process known as'remote viewing.' The experience of remote viewer Ingo Swann was first revealed in 1998 when he explained how his psychic episode took him to the dark side of the moon, a region that always faces away from Earth and out of sight from human eyes. That's where the remote reviewer made a shocking discovery: towers, buildings, and human-like aliens working at a secret complex on the moon's surface. Disturbingly, Swann said government officials knew the aliens had a base there, and these humanoids could actually sense his presence as he viewed them with his mind from 238,000 miles away.

An influential group of researchers is making the case for new ways to search the skies for signs of alien societies. They argue that current methods could be biased by human-centered thinking, and that it's time to take advantage of data-driven, machine learning techniques. The team of 22 scientists released a new report on August 30, contending that the field needs to make better use of new and underutilized tools, namely gigantic catalogs from telescope surveys and computer algorithms that can mine those catalogs to spot astrophysical oddities that might have gone unnoticed. Maybe an anomaly will point to an object or phenomenon that is artificial--that is, alien--in origin. For example, chlorofluorocarbons and nitrogen oxide in a world's atmosphere could be signs of industrial pollution, like smog.

The Robert C. Byrd Green Bank Telescope in West Virginia is one of several helping to search for alien civilizations.Credit: Jim West/Alamy From the hills of West Virginia to the flats of rural Australia, some of the world's largest telescopes are listening for signals from distant alien civilizations. The search for extraterrestrial intelligence, known as SETI, is an effort to find artificial-looking electromagnetic radiation that might have come from a technologically advanced civilization in a far-away solar system. A study published today1 describes one of several efforts to use machine learning, a subset of artificial intelligence (AI), to help astronomers sift quickly through the reams of data such searches yield. As AI reshapes many scientific fields, what promise does it hold for the search for life beyond Earth? "It is a new era for SETI research that is opening up thanks to machine learning technology," says Franck Marchis, a planetary astronomer at the SETI Institute in Mountain View, California.

In this special issue we are reprinting our top stories of the past year. This article first appeared online in our "Wonder" issue in February, 2021. Suppose aliens existed, and imagine that some of them had been watching our planet for its entire four and a half billion years. What would they have seen? Over most of that vast timespan, Earth's appearance altered slowly and gradually. Continents drifted; ice cover waxed and waned; successive species emerged, evolved, with many of them becoming extinct. But in just a tiny sliver of Earth's history--the last hundred centuries--the patterns of vegetation altered much faster than before. This signaled the start of agriculture--and later urbanization.

When I lived in the Bay Area, I used to get together with my friend Jaron Lanier to explore the implications of spectacularly weird thought experiments. Outlandish thought experiments have been essential in the intellectual history of science, but the point isn't the weirdness itself. The payoff of thinking about strange things like Schrödinger's cat, the infamous cat that is alive and dead at the same time, is not necessarily that we should then "believe" in the existence of such a cat. Instead, we can hope that uncommon ideas will shed light on the murky margins of our thoughts; in the case of Schrodinger's cat, in dealing with the question of superposition. The point is not to confuse or bamboozle people, but to eventually find a way to think that makes more sense and is a little less murky.

Suppose aliens existed, and imagine that some of them had been watching our planet for its entire four and a half billion years. What would they have seen? Over most of that vast timespan, Earth's appearance altered slowly and gradually. Continents drifted; ice cover waxed and waned; successive species emerged, evolved, with many of them becoming extinct. But in just a tiny sliver of Earth's history--the last hundred centuries--the patterns of vegetation altered much faster than before. This signaled the start of agriculture--and later urbanization. The changes accelerated as the human population increased. Then came even faster changes.

You might imagine that in the midst of a global pandemic and all of its social and economic fallout that our minds would be laser-focused on immediate, Earthly woes. A case in point is the recent virus-like spread of news headlines to the effect that there should be "at least 36 alien civilizations" in our galaxy. There you have it, three dozen other sets of intelligent life dotting our cosmic neighborhood, so stick that in your pipe and smoke it. It's at times like these that you can almost hear the collective sigh from astronomers and astrobiologists who realize that they have to roll up their sleeves to gently, politely, carefully try to explain why these headlines are, shall we say, of the same nature as the matter that emanates from ruminant digestive systems. Charting the development of civilizations as a simple function of the age of life on a planet seems positively ludicrous.

You might imagine that in the midst of a global pandemic and all of its social and economic fallout that our minds would be laser-focused on immediate, Earthly woes. A case in point is the recent virus-like spread of news headlines to the effect that there should be "at least 36 alien civilizations" in our galaxy. There you have it, three dozen other sets of intelligent life dotting our cosmic neighborhood, so stick that in your pipe and smoke it. It's at times like these that you can almost hear the collective sigh from astronomers and astrobiologists who realize that they have to roll up their sleeves to gently, politely, carefully try to explain why these headlines are, shall we say, of the same nature as the matter that emanates from ruminant digestive systems. Charting the development of civilizations as a simple function of the age of life on a planet seems positively ludicrous.

While some researchers search for biological signs of life beyond Earth, others are scouring the cosmos for technosignatures -- evidence of the kind of technological activity we might expect from an advanced alien civilization. This evidence could take a range of forms. It might be a series of radio signals, signs of pollution in an exoplanet's atmosphere, or even an engineered structure. A new study suggests, however, that we might want to think twice about using artificial intelligence to help in our hunt for technosignatures -- because it could trick us into thinking we see signs of aliens where none exist. Here's an example of how it could go down.

January 5, 2018 --The idea that there might be gigantic alien structures orbiting a distant star just bit the dust. After citizen astronomers spotted data in 2015 revealing that KIC 8462852, a star about 1,000 light years away, was dimming and brightening in a strange way, one of many explanations proposed by astronomers involved some sort of "megastructures" orbiting the star – perhaps built by aliens to harvest stellar energy. That imaginative suggestion rocketed the star to fame. But Louisiana State University astronomer Tabetha Boyajian and colleagues collected more data on the star, nicknamed "Tabby's Star" for Dr. Boyajian, and they found that the star's strange flickering was thanks to something much more mundane: ordinary dust. We see it in many different ways, and the data that we took showed a clear signature of this being what we would see from dust," Boyajian says. This may be a disappointing outcome for those hoping for proof of an alien civilization. But Tabby's Star's rise to stardom highlights a deeply entrenched human psychological quirk: When presented with a puzzling phenomenon, our knee-jerk instinct is to ask not what created it, but who. Scientists say that as social animals, we are evolutionarily predisposed to see agency and intentionality in the world around us. And when it comes to astronomical mysteries, aliens seem to fit. "It's the duct tape of science," says Seth Shostak, senior astronomer for the SETI Institute. Because we don't know what aliens might do, they could explain anything. But why do we do that? "It's not just aliens," says Christopher French, a psychologist and founder of the Anomalistic Psychology Research Unit at Goldsmiths, University of London. "We do have a natural tendency to assume that anything odd, or, superficially at least, inexplicable, that there must be some sort of intentionality behind it, some sort of intelligence, there must be a purpose, somebody or something has done that for a particular purpose.