Neither the wreckage of the spacecraft that supposedly crashed at Roswell, New Mexico, in 1947, nor the corpses of its alien crew have ever been put on display. Breakthrough Listen, the $100 million alien-seeking program launched in 2016 by Stephen Hawking and tech billionaire Yuri Milner has produced no results. Countless reported sightings of U.F.O.s and accounts of often painfully intimate alien abductions have come to nothing. Mars and assorted asteroids have failed to produce swarms of alien microbes.
Nevertheless, there is a slim chance that, in the next decade or so, all of that will change and we shall find that we are not entirely alone.
The cosmos is 93 billion light-years across, with perhaps 2 trillion galaxies each containing hundreds of billions of stars and, as we can now be pretty sure, hundreds of billions of planets. And yet still we see and hear nothing. There seems to be only what the French mathematician and physicist Blaise Pascal called “the eternal silence of these infinite spaces.” Extraterrestrial life, if it exists, is either very well hidden or just too far away in time and space.
There are two equally rational responses to the existence of extraterrestrial life in this ultimate vastness. The first is that size doesn’t matter — life is such an improbable outcome that it may well have happened only once. We are here by the skin of our teeth. There is also the problem raised by the physicist Enrico Fermi. “Where are they?” he asked. Say a technologically advanced civilization could produce spaceships capable of one-tenth the speed of light — around 18,600 miles per second. At that speed, it would take only a million years for them to populate the entire galaxy. But it hasn’t happened, so they are not there.
The second response is that size does matter. Life is not that improbable — the process is, as one scientist put it to me, “thermodynamically downhill.” Life may still be unusual, but it is, nevertheless, almost certain to have happened more than once, because of the physics and scale of this particular cosmos.
Tantalizingly, this could all be resolved in an instant. Say we found a simple, non-terrestrial organism on an asteroid, on the Saturnian ice moon Enceladus or the Jovian moon Europa — currently two of the most promising sites for life in the solar system. The mere fact that life had appeared twice in one small corner of the galaxy would make it a near certainty that our galaxy and the universe are teeming with life, some of which will certainly be intelligent and probably most of which will be more technologically adept than us. The universe is 13.8 billion years old, humans have been around for only 300,000 years; inevitably some, perhaps all, aliens will be well ahead of humans.
But would it make any difference to the human experience and imagination if we did find life, intelligent or not? We would remain locked in time, space and our brief lives, unable to make contact over such distances. The answer, judging by the intensity and persistence of various alien mythologies, is that it would.
There have always been speculations about life on other planets. But the moon, Mercury, Mars and Venus have over time been proved uninhabitable by space exploration. Contemporary speculations, meanwhile, have tended to be either wrongheaded or cultish.
Mars, until quite recently, was still in contention thanks to the Italian astronomer Giovanni Schiaparelli who, at his death in 1910, was regarded as Italy’s greatest scientist and astronomer. Though intensely serious and conscientious, he made some odd mistakes on the basis of his faith in a teeming cosmos. His worst mistake was his discovery of “canali” on Mars, vast engineering works clearly constructed by intelligent and competent Martians who, thanks to Schiaparelli, stalked 20th-century imaginations. In fact, his telescope had deceived him by resolving random surface features into straight lines.
Another cultish prophet was Kenneth Arnold, a businessman and pilot who, while flying near Mount Rainier in Washington in June 1947, spotted a squadron of nine alien craft traveling at an estimated 1,200 miles per hour. That news, combined with the febrile atmosphere of the early years of the Cold War and the nuclear age, started the contemporary alien craze in fact and fiction.
Two weeks or so after the Arnold sighting came the Roswell incident. What the U.S. Air Force said was a crashed weather balloon became, in the minds of the ufologists, a flying saucer that, together with its occupants, was said to be kept at a secret base known as Area 51. In fact, the Air Force was lying. Years later, it was revealed that the object was a nuclear test surveillance balloon. Regardless, for the next 60 years, usually small and usually green aliens with large slanting black eyes flooded television screens and movie theaters.
The scale of the obsession attracted the attention of the psychologist Carl Jung who, in 1958, published “Flying Saucers: A Modern Myth of Things Seen in the Sky.” For him, the alien craft were psychic projections. But why were they happening then?
“In the threatening situation of the world today,” he wrote, “when people are beginning to see that everything is at stake, the projection-creating fantasy soars beyond the realm of earthly organizations and powers into the heavens, into interstellar space, where the rulers of human fate, the gods, once had their abode in the planets.”
This rings true. When I was working on a book on the subject (“Aliens: Why They Are Here”), the true believers, the U.F.O. spotters and the extraterrestrial visionaries I spoke to, had one thing in common. There was, among them all, a yearning that rose to a desperation for it all to be true.
An alien revelation would explain or heal the undefined unease they felt about the human condition. This unease could be expressed as suspicion of governments, apocalyptic anxieties, religious longing or simply a need for their lives to become less banal, less limited. Jung may have been right to regard the specific objects of these longings — aliens — as a contemporary phenomenon. But the longing, surely, is timeless.
Neither Jung’s diagnosis nor the quality of most of the claimed sightings would have been much help to the various SETI — search for extraterrestrial intelligence — projects around the world. Just as unhelpful were the fictional versions of alien contact. Highly competent films like “Contact,” “Close Encounters of the Third Kind” and “Arrival” picked up the themes of postwar alien stories, but they did so as mythologies: human stories with human messages. The dominant theme seemed to be: We went in search of aliens and found ourselves. Or, to put it another way, we are the aliens.
This even applied to the more pessimistic alien movies. In “The Day the Earth Stood Still,” made in 1951 during the first wave of popular fascination with extraterrestrial contact, an alien called Klaatu arrives and tells earthlings, “If you threaten to extend your violence, this Earth of yours will be reduced to a burned-out cinder.” Aliens, indignant at human savagery, would arrive to tell us we were the monstrous aberrations in the cosmos. But even Klaatu was not alien enough, he was just another off-the-shelf hellfire preacher.
More imaginative alien fiction — in, for example, the works of Stanisław Lem or the Strugatsky brothers — raises the possibility that the aliens simply would not care about us or would lie beyond human comprehension. Non-fictionally, however, some think it is possible that the mere fact of the existence of aliens would raise up our species.
“In my opinion,” wrote the physicist Paul Davies in his book “Are We Alone?”, “the most important upshot of the discovery of extraterrestrial life would be to restore to human beings something of the dignity of which science has robbed them. Far from exposing Homo sapiens as an inferior creature in the vast cosmos, the certain existence of alien beings would give us cause to believe that we, in our humble way, were a part of a larger, majestic process of cosmic self-knowledge.”
So, one way or another, yes the discovery of extraterrestrial life would make us stop and think. But is it going to happen?
Three developments suggest that we may be closer to an answer than we once thought. The first dates back to the 80s and the discovery of extremophiles: microbes found in extreme environments that were previously considered unable to sustain life. A whole menagerie emerged — hyperthermophiles that could survive in temperatures above 80 degrees Celsius (176 degrees Fahrenheit), acidophiles that could live in acids, even radioresistant creatures that could live happy amidst high levels of radiation. Extremophiles revealed that our previous conception of the conditions necessary for life was far too narrow. We should be looking in a far greater range of locations.
One such location would be the planet Venus, which has a surface temperature of nearly 900 degrees Fahrenheit and clouds made of sulfuric acid. Phosphene, a chemical regarded as a “biosignature” — a sign of life — has been detected in the Venusian atmosphere. This is the closest planet to Earth. If life is there we could pretty much assume it is everywhere.
The second recent development is a series of unexpected discoveries elsewhere in our own solar system. The most startling came from NASA’s Cassini mission, launched in 1997, which conducted several flybys of Saturn’s ice-covered moon Enceladus. These revealed that there were plumes of water rising from its surface. It was clear that there was an ocean beneath the frozen surface that was warm and nutritious enough — in the form of hydrogen and carbon dioxide — to support microbial life. In addition, the Hubble Space Telescope has detected plumes rising from the Jovian moon Europa. Sub-surface lakes or oceans are, in theory at least, habitable environments.
But, as with Venus, such environments are probably only for dumb bugs. Nobody is now hoping for intelligent life in our solar system.
For that we will have to look further and, soon, we shall be able to with quite staggering accuracy. What we shall be looking for is the “red edge,” a suitably dramatic name for what would be a very dramatic discovery.
This possibility arises from the detection in October 1995 of 51 Pegasi b, a huge Jupiter-sized planet 50 million light-years from Earth. It was the first clear discovery of an exoplanet, a planet beyond our solar system, and, it was orbiting a “main sequence” star like our sun. Since then, 4,306 other exoplanets have been discovered.
This may not seem so surprising — why would other stars not have planets? But the point is we did not know and, furthermore, we had no means of detecting them. Still today we cannot “see” planets that far away because of the brilliant light of their stars; instead, we detect slight changes in the star’s luminosity or signs of wobbling caused by the gravitational effects of an orbiting planet.
At once, the aliens were back and neo-ufologists were on the case. The longing, the yearning for it all to be true, had returned. In 2015, an apparently innocuous scientific paper reported a discovery of something large passing in front of a star 1,500 light-years away. The true believers claimed it was evidence of an “alien megastructure” — a Dyson Sphere, to be exact, an idea that first appeared in a novel by Olaf Stapledon called “Star Maker” and was later given respectability by the physicist Freeman Dyson. The sphere would be a vast structure built around a star to maximize the retrieval of energy — potentially essential for an advanced species.
“I’m sure it’s aliens,” I said to tease the exoplanet hunter Mark Wyatt at Cambridge, one of the researchers behind the paper.
“I’m sure it’s not,” he replied.
The problem with exoplanets is we cannot see them, we can only detect them. Soon, however, we will have a form of seeing called spectroscopy.
Next year, the James Webb Space Telescope will be launched. This is the long-delayed successor to the Hubble Space Telescope. And in 2025, the Extremely Large Telescope (E.L.T.), a European project under construction in Chile, will go online. Both are vastly more powerful than the Hubble, and the E.L.T. will be specifically examining exoplanets.
This is where the red edge comes in. At certain wavelengths, the vegetation on Earth becomes highly reflective in the near-infrared range of the light spectrum — the red edge. If we can detect it or some related phenomenon in the spectra of exoplanets, then it may be a sign of life. Of course, it may only be vegetation — exoplants — rather than anything more exciting. But it will be an enormous step, establishing the principle of extraterrestrial life. Eventually, the discovery of such biosignatures will be joined by techno-signatures — signs of technological sophistication that must now be making the Earth ever more conspicuous to any alien seekers. But that could be decades away.
There may, however, be a problem. Once again, we are expecting the aliens to be like us. If we are seeking cuddly extraterrestrials, we may be too late. As Martin Rees, Britain’s Astronomer Royal, pointed out in a lecture a couple years ago, organically based intelligence may be just a “brief interlude before the machines take over.” Machine intelligence is faster and more robust than human intelligence, and would seem to be a logical next step in evolution. So on a planet orbiting a star much older than our own, we may only find non-biological beings. Or we may not find them there at all — they may have emigrated to space to escape the kind of planetary crises we are now confronting.
So, as Rees put it, we would be most unlikely to “catch intelligence” in the brief sliver of time in which it was embodied in flesh and blood. “The lifetime of an ‘organic’ civilization may be millennia at most. But its electronic diaspora could continue for billions of years.”
He went on to list three aspects of the alien entities we are likely to encounter: “They will not be ‘organic’ or will not remain on the planet where their biological precursors lived. But we won’t be able to fathom their intentions.” That last point is a killer for alien optimists. As the philosopher Ludwig Wittgenstein wrote, “If a lion could speak, we would not be able to understand him.” We can be confident that any alien is likely to be more different from us than a lion.
This may not be an absolute disappointment. We would know we shared the cosmos with intelligent, technologically adept creatures and that, therefore, we would no longer be entirely alone, even though their intentions would be unfathomable.
In alien fiction, machine beings usually appear as nasty creatures, unable to grasp the warmth and depth of the human soul. Alone in this menagerie, Data, the “Star Trek” android, aspires to be more human; the rest seem to despise our emotion-laden weakness. But even expecting aliens to be nasty is glib anthropomorphism. Why should they not be entirely opaque and indifferent to their human neighbors in the cosmos?
For the moment, aliens are nothing more than blank sheets of paper scribbled over with human longings and anxieties. Jung would be even more topical right now than he was in 1958. Thanks not just to nuclear weapons but also to global warming, increasingly brutal geopolitics and pandemics, everything clearly is at stake. Aliens on distant planets are, once again, “the rulers of human fate, the gods.” If we do find them in the near future, then, opaque as they may well be, they will at least provide evidence that we are not alone in bearing the burden of consciousness.