Advances in astronomy and science make it more clear by the day that, unexpectedly, the math is on the side of aliens. As late as the 1990s, scientists weren’t sure that there were planets anywhere else in our galaxy or in the universe beyond, but advances like the Kepler Space Telescope have led astronomers to believe now that nearly every star is like our sun, possessing so-called “exo-planets,” and that, by extension, there are many habitable planets with conditions to support life as we recognize it. 

Recent estimates imagine that there are one sextillion — a billion trillions — of habitable planets in the universe. Sure, the odds of life are long, but does it really seem like humans and intelligent life are a one-in-a-sextillion chance? That wonder “Are we alone?” is one of humanity’s most profound questions, alongside “Is there a god?” and “what happens after death?” And as nearly every day brings additional evidence we’re likely not alone, it sparks the human mind to wonder if and how we might someday discover, definitively, that we’re not. I spent the last two years digging into this science as part of my research for my new book, UFO: The Inside Story of the US Government’s Search for Alien Life Here—and Out There, and came to realize that we’re living through a startling transformation right now of our understanding of the universe and that the possibility of life and intelligent life “out there” is moving quickly toward a probability.

Simon & Schuster

It would be one of the most startling transformations of humanity’s understanding of itself and our place in the universe — a discovery with profound implications for everything from religion to science to politics, an answer to one of the most basic and fundamental questions of our existence.

Hollywood, science fiction, and popular culture has imagined that moment for centuries—from the benign and fun, Alf and E.T., to the destructive, like the Alien franchise or Invasion of the Body Snatchers. And yet the more we understand about the universe — and our tiny place in it — the more it also seems that everything we’ve imagined about that “first contact” moment is probably wrong.

Hollywood and pop culture has given us two clear ideas of what “first contact” would look like: There’s the dramatic signal from space, a la Jodie Foster and Contact, the message that sends humankind reeling for answers, and then there’s the even-more-ominous “Take me to your leader” scenario, where the alien mothership appears over a landmark like the White House, usually as a precursor to a massive invasion, a la Independence Day.

The truth is that our first sign of an advanced extraterrestrial civilization is almost certainly going to be far more mundane and ambiguous. Here’s what science is learning about alien life and how contact might occur:

Intelligent life is probably far away. Very far away. The more scientists have come to understand just how likely life could be, given the huge number of habitable planets across the universe, the more they’ve realized that the universe itself is far larger than we ever imagined. The math may very well be on the side of the aliens existing, but that’s largely because the math of the universe itself turns out to be astounding. In recent decades, astronomers have made a lot of progress understanding the sheer scale and breadth of the universe — and even if life is “close by” in astronomical terms, it could still be so far away from us that we’d likely never know it existed. 

We now understand that our own Milky Way galaxy is about 2.5 million light years away from the next closest galaxy, known as Andromeda. Together, these two massive galaxies — and all the stuff in between them, including a number of so-called dwarf galaxies and satellite galaxies, as well as a third large galaxy known Triangulum — make up what astronomers call the “Local Group,” which is just one corner of a larger cosmic structure known as a “supercluster.” If the Milky Way is our neighborhood, then think of the “supercluster” as the cosmic suburb in which we exist. In 2014 a team of astronomers led by Hawaii’s R. Brent Tully drew a more precise boundary of this galactic map — they dubbed our supercluster “Laniakea,” Hawaiian for “immense heaven,” and it stretches across more than 520 million lightyears of outer space. Our “supercluster suburb” encompasses about 100,000 other galaxies that astronomers define as “nearby,” which is to say that we could have a lot of “close neighbors” and probably still never know. 

We might have missed the chance for first contact already. Our solar system is actually quite young, just about 4.5 billion years old in a universe that’s closer to fourteen billion years old. The James Webb space telescope has been rewriting our understanding of galaxy formation and has photographed a galaxy far, far older than anything we’d imagined — one that formed just 390 million years after the universe began. 

We now believe that the first primitive life emerged on Earth just a half-billion years after it formed — an astronomical blink of the eye, and a fact that makes it seem more likely that life exists in many places — and life has evolved relatively rapidly since. Put those discoveries and history side-by-side and it’s suddenly possible to imagine incredibly advanced civilizations — ones that last hundreds of millions or even a billion years, levels of sophistication that boggle our 200,000-year-old human imagination — that could have risen and fallen across those eight or ten billion years between the beginning of the universe and when our own solar system was formed. We might feel alone now simply because we’ve missed civilizations far grander than ours by a billion or two years.

If aliens exist, we probably don’t matter to them at all. There’s an obvious human-centric nature to the way we think of alien visitors — imagining them bothering to cross the vast distances of space just to, variously, buzz us in their mysterious flying saucers, make friends, abduct us, invade us, or harvest humans for food or energy. The truth is probably no one knows we’re here—or cares. We’re a young civilization in a very ordinary corner of the universe. As Stephen Hawking bluntly summarized it: “The human race is just a chemical scum on a moderate-sized planet, orbiting around a very average star in the outer suburb of one among a hundred billion galaxies.”

Even advanced telescopes from far away would pick up no visible signs of life on Earth — just so-called “technosignatures” of a planet that has water and oxygen. And for all the imagination that other civilizations would pick up our radio and television broadcasts, like Hitler’s opening of the 1936 Olympics (one of the first major broadcasts) or the Superbowl (the most powerful, frequent signal we broadcast into space), no human signal has journeyed even 100 light years yet, a distance that covers only a sliver of the universe, even if the signal remains detectable across that distance. Even powerful telescopes or visiting craft from “nearby” alien civilizations could have looked at Earth not that long ago and with even relatively advanced technology and missed that we existed at all — go back just 10,000 years or so and human settlements would have been all-but invisible to surveillance from space.

Carl Sagan, the famous astronomer who was one of the strongest proponents of the search for extraterrestrial life in the 20th century, used to dismiss reports of UFOs as signs of alien visitation by arguing that, statistically, aliens probably swing by Earth only about every couple hundred thousand years, passing by on the way from one place of interest to another, much in the way that you might stop at a rest area on the New Jersey turnpike. The idea that anyone happens to be stopping by now — right now — to check on humans is all but impossible to imagine.

That’s if they’re looking for us at all. In my recent research on extraterrestrial life and UFOs, one of the most poignant thought experiments was the question of whether our own human longing to reach for the stars may exist elsewhere — or even occur to other species. There is growing evidence that there are perhaps many marine environments across the universe, including not just planets but moons with vast oceans far deeper than our own. (There are at least two of these so-called “ocean moons” in our own solar system: Saturn’s Enceladus and Jupiter’s Europa, which has sixty-mile-deep oceans underneath six miles of ice.) Perhaps these “ocean moons” or “ocean planets” have hot deep-sea vents like Earth, the intense and wild environments where scientists increasingly believe might be one of the possible places that life began here. Extrapolate a bit from there, and there could be all manner of life-supporting marine planets, filled with creatures equivalent to our highly intelligent whales and dolphins — creatures that surely pass the “intelligent life” test — and yet who have never glimpsed the Milky Way above and wondered about journeying to the stars.

Taken together, these factors — that intelligent life is probably far away and doesn’t care about us, or perhaps we missed it entirely — and you end up with another startling realization: We probably will first detect an advanced civilization through its trash.

If — or when — we see evidence of another advanced civilization, it’s most likely not going to be on purpose or because they intended to visit us or our solar system. It’s probably not even going to a true spacecraft in the way we imagine them to be. We’re probably, instead, going to see the interstellar equivalent, as Harvard astronomy chair Avi Loeb says, of an empty plastic bag blowing through our cosmic backyard — a remnant of a spacecraft, probe, or other long-defunct or forgotten garbage launched out into the universe by other civilizations. Signs of life elsewhere, if and when it appears, might be less definitive and illuminating than we imagine, the galactic equivalent of a puzzling artifact on an archeological dig: What did they use this for?

There might well be more of these types of cosmic interlopers than we realize: Just a decade ago, we’d never detected an interstellar object — an object that crossed into our solar system from another — but now we’re realizing they’re semi-common. In 2017, astronomers using the PAN-STARRS telescope in Hawaii detected something unusual passing through from outside our solar system — they dubbed it ʻOumuamua, Hawaiian for “scout,” and it was formally known as 1I/2017, e.g., the first interstellar object. (ʻOumuamua passed by too quickly for careful study, but its known characteristics were strange enough that astronomers still debate it — believing it might be a never-before-seen type of meteor or planetary fragment, or perhaps even an extraterrestrial craft.) It took only two years for astronomers to detect the second known interstellar object, a comet now known as 2I/Borisov. And this summer, Loeb, who heads the Galileo Project that’s trying to advance the search for extraterrestrial intelligence, led an expedition to the coast near Papua New Guinea to search for pieces of an interstellar meteor that evidently hit Earth in 2014 — one of several such interstellar meteors that astronomers have discovered in recent years through mining US government meteor data. There’s a lot more low-hanging fruit to study: Astoundingly, we haven’t even comprehensively surveyed the surface of the moon yet to see if there’s another moon lander or craft that another civilization left behind, just as we did with our rover from the Apollo program.

Humans, after all, have in just a few decades launched five interstellar objects ourselves, like the Voyager space probe, which in 2012 became the first manmade object to cross the heliosphere out of our solar system. Perhaps one day, another civilization will detect it and wonder of its origins. If we’ve launched five in the few decades we’ve been exploring space, imagine again the space debris that might accumulate from a civilization across millennia or even millions of years.

There’s another intriguing possibility about life beyond, too: Other civilizations might be so much more advanced, we may not even recognize or notice when they pass by. As advanced as our technology and our scientific understanding of physics may seem, we are probably galactically primitive; after all, we’re just barely a century into the age of flight and half that into the computer age, and much of what we know about physics has unfolded in just a single human lifespan. As Sagan argued in the 1970s, “There is almost certainly no civilization in the galaxy dumber than us that we can talk to. We are the dumbest communicative civilization in the galaxy.”

Even as tools like the James Webb telescope rewrite our understanding of history and the universe, our space-watching technology and universe surveillance tools cover a minuscule fraction of the sky. We only detected ʻOumuamua because it was larger than a football field, which is about the lower limit of our current ability to detect objects in space. Similarly, almost any civilization capable of interstellar exploration would have to figure out how to travel at some fraction of the speed of light, and we don’t really have any way to detect objects moving that fast through our solar system. That means our solar system could be regularly being criss-crossed by smaller crafts or fast-moving probes and, for now, we would none the wiser.

“They” might already be “here,” and we just don’t know.


Journalist and historian Garrett M. Graff is the author of “UFO: The Inside Story of the US Government’s Search for Alien Life Here―and Out There.” His previous book “Watergate: A New History” was a finalist this year for the Pulitzer Prize in History.