Every evening in Maui, a telescope perched atop a volcano captures particles of light in the universe with the world's largest digital camera. Normally it searches for asteroids dancing across the cosmos. But one night last October, it locked its gaze onto something remarkable, an unidentified flying object moving quickly through space, seemingly from another solar system.
Or at least that's what astronomers at the University of Hawaii concluded when they discovered it. At first, they thought it was a comet, then an asteroid. But within a month, they realized the object was long and thin and unlike any asteroid known to science. They named it 'Oumuamua—a Hawaiian word that means "messenger from the distant past."
Thousands of miles away, a Harvard astronomer named Avi Loeb learned of the mysterious object as well. Soon, he began pondering an enticing possibility: that 'Oumuamua was actually an alien spacecraft sending signals back to its creators. This theory may sound a bit out there. But Loeb isn't some crackpot looking for little green men in a spaceship. He and his colleagues are part of a growing number of top-tier scientists who are applying the same rigorous standards they use on other scientific issues to tackle one of the biggest questions facing humanity: Are we alone in the universe?
Americans have long been fascinated by the possibility of alien visitors. A 2001 Gallup Poll (the most recent one available) found that 33 percent of Americans believed aliens have visited the Earth. But scientists—both inside and outside the U.S. government—have been reluctant to take such claims seriously. From the 1947 weather balloon crash in Roswell, New Mexico, to crop circles in England, they've largely joined the debate only to debunk some very dubious claims. They've also lamented the lack of distinction most people make between alien landings—which haven't occurred—and the possibility of future alien contacts (which could indeed happen). "We always get the UFO question," says Dan Werthimer, astronomer at University of California, Berkeley. During public appearances about the search for alien life, Werthimer says, people often say, "why bother, because E.T.'s already landed here and kept secret in some military installation."
But while UFO claims are often hoaxes or the work of conspiracy theorists, the search for extraterrestrial intelligence—alien life just as smart and technologically advanced as humans—is a legitimate scientific field. Driving this quest to find life on other planets: hundreds of millions of dollars and super-powerful new telescopes that look ever deeper into the universe.
Experts disagree on how intelligent life might try to contact humans. But the resurrected field, known as SETI, is largely based on the assumption that extraterrestrials—if they are out there and actually trying to chat—might use the same type of tech that we use to communicate with one another—from radio signals to flashes of light.
Yet that conjecture speaks to SETI's central irony. Just as our attempts to find extraterrestrials are becoming more advanced, just as scientists are increasingly confident we aren't the only intelligent beings in the universe, humans are creating more technology-produced noise than ever before, undermining our ability to detect potential alien transmissions.
In fact, SETI scientists say, we are making so much noise, if E.T. tried to phone our home, we might never get the message.
Look Who's Talking
In 1950, Nobel Prize–winning physicist Enrico Fermi articulated a riddle—now known as Fermi's paradox—that speaks to a core question SETI scientists are trying to answer: If intelligent life exists elsewhere in the universe, why haven't we found it yet? Since experts estimate the universe is nearly 14 billion years old, you'd think it would be populated with civilizations other than our own.
One problem: money. The search for extraterrestrials is very expensive. And the U.S. government and private universities have mostly avoided funding the required research. The first professional SETI conference, held in Green Bank, West Virginia, was in 1961, just months after Soviet cosmonaut Yuri Gagarin became the first person to travel into space. In the 1980s, NASA devoted $1.5 million to $2 million per year to the search for sentient life in outer space, and in 1990, Congress approved $100 million for new technology—a significant amount of funding for the field. But just a few years later, NASA axed that program. "Not a single Martian has said, 'Take me to your leader,'" Democratic Senator Richard Bryan of Nevada said during the budget vote that canceled the funding. "And not a single flying saucer has applied for FAA approval." NASA hasn't funded SETI research since, a decision that pushed aliens to the fringes of astronomy.
Yet in 2015, SETI researchers finally received the necessary funding. And it came in a plot twist reminiscent of the movie Contact—in which a SETI researcher clashes with government authorities, only to be rescued by a mysterious billionaire.
In real life, SETI's wealthy benefactor isn't secretive. His name is Yuri Milner, and he's a Russian physicist and venture capitalist. Named for Gagarin, he sees it as our "galactic responsibility" to acknowledge the profound luck of our intelligence—and search elsewhere for its equal. He also dreams about the impact such a discovery would have on humanity. "There are these moments, that are very rare, that we all feel like one," he says. "The rest of the time, we are divided."
Milner decided to bankroll the search for extraterrestrial intelligence, pledging $100 million over 10 years for an international project called Breakthrough Listen. "Obviously, there's no guarantee," he says. "The chance of finding it in the next 10 years is small. [But] the significance of that potential discovery is so large that even the small probability justifies the effort."
About a third of Milner's funding goes to the SETI program at the University of California, Berkeley. Andrew Siemion, its alien hunter in chief, stumbled onto the field after 9/11 left him searching for meaningful work. Since then, he has dedicated his career to trying to find a sign—any sign—that can be explained only by the existence of technologically advanced alien life. "The most interesting property of the universe is the fact that intelligent life exists within it," he says. Siemion is determined to find out if it exists beyond Earth. "I believe it to be the most fundamental question we can ask as scientists."
Milner's money has vastly improved Siemion's ability to tackle that question. The funding has given him and his colleagues the ability—and time—to stare across the universe, using some of the most powerful telescopes on the planet. "It's an absolute revolution in our capabilities," he says.
Most of these instruments are radio telescopes—giant, ultra-sensitive dishes that receive faint signals from very far away. Yet these instruments don't search the cosmos for sound; they search it for light. Radio waves constitute a portion of the light spectrum—the band that alien technology would most likely use to reach us, many astronomers believe.
Alien hunters look for radio waves because humans are so fond of using them. Radio waves can travel miles, letting us hear our favorite talk show while we drive. They can also traverse light-years and be crammed with information, which is why they carry our television broadcasts, our mobile calls and GPS locations. Because radio waves are so versatile, SETI scientists believe our galactic neighbors might use them to reach out and say, "Sup?"
Scientists classify radio waves by how often they crest; that measurement is the wave's frequency. The tighter the crests, the higher the frequency. When it comes to radio waves from beyond Earth, scientists tune to frequencies between 1 and 10 gigahertz. "That's the range in which our atmosphere is pretty transparent and the galaxy is pretty quiet," says astronomer Jill Tarter of the SETI Institute in Mountain View, California, which has long been the leader in the field. Going below that window catches too much noise from the rest of the galaxy, like radiation from planets or even the humming of a distant black hole. The atmosphere blocks frequencies higher than about 10 gigahertz. But nestled in that quiet window are 9 billion possible frequencies, or channels, that aliens could be using.
When the modern search for extraterrestrial intelligence began in the 1960s, scientists could listen to just one channel at a time. Today, they can tune in to tens or even hundreds of millions of channels at once, listening for a single note from faraway millions of times over. This vast capacity increases the odds of us catching an alien message when it arrives. But it also delivers a ridiculous number of other signals. "Every 10 seconds, you get a signal," says Seth Shostak, a senior astronomer at the SETI Institute. "You'd go nuts if you had to look at all this stuff."
The new era of SETI is rapidly expanding the investigation. Milner's money gives Siemion at Berkeley the means to purchase blocks of expensive observing time on some of the most powerful radio telescopes in the world—from West Virginia to China. Scientists are looking at more stars, gathering weaker signals and eavesdropping on new regions of the sky, like the barely studied Southern Hemisphere, the gateway to the crowded heart of the Milky Way.
The infusion of cash helps not only expand the search but also rule out possibilities. We have no galactic caller ID, and so every plausible signal must go through a battery of tests to confirm whether it's E.T. on the other end of the line. So far, not a single signal has passed those tests.
Yet as Tarter famously put it, concluding that we must be alone, simply because we haven't heard aliens yet, is like scooping up a cup of seawater and deciding there are no fish in the oceans. Scientists have calculated we need to comb about a million star systems to find new friends.
So far, says Shostak, "we've looked at only a few thousand."
Alien Emojis
Beginning in 1998, an unidentified radio signal left astronomers at the Parkes Observatory telescope in New South Wales, Australia, stumped. They knew the sound was coming from somewhere nearby, but they had no idea of what it was. Finally—after 17 years of searching—they found the culprit: impatient staffers opening a microwave oven while it was still running.
Though SETI scientists believe aliens would likely use similar technology as we do on Earth, that assumption poses a fundamental, possibly insurmountable, challenge to their search: Our own chatter makes it immensely difficult. Cellphones, Wi-Fi and GPS all rely on radio waves. Those waves occupy the same channels researchers use to listen to for E.T. And because our devices are so much closer to the telescopes, the signals are much stronger. "If E.T. is broadcasting in the cellphone band," says Werthimer, "we'll never find him." Every time we text an emoji, we potentially make SETI research more difficult. Sorting the alien wheat from the human chaff, says Siemion, is the hardest part of the search for extraterrestrial intelligence.
Local regulations mitigate the interference. South Africa is currently building a massive array of radio dishes and trying to move local television and phone service to radio-free technology to reduce the disturbance they will otherwise pose. Federal and state quiet zones shelter the Green Bank Telescope in West Virginia, and its staffers help neighbors produce less interference. Sometimes, they even drive around in a van equipped with a radio antenna to track down chatter.
But such measures aren't enough. Astronomers want to build telescopes in places where there are fewer people, but it's not easy. The remote location of the Parkes telescope might make it conducive for hearing E.T., but it also increases the risk of disruption from livestock. The electric fences corralling the animals emit radio waves that interfere with SETI work more than cellphones do. "We probably have more problems with cows around Parkes than these other things," says Matthew Bailes, an astronomer at the Swinburne University of Technology in Australia. Nearly everything we do generates signals, and eliminating them essentially means eliminating modern life.
Even when the land is silent, though, radio interference still comes from above. An ever-increasing number of satellites broadcast signals from the sky that radio telescopes pick up. Eradicating this sort of interference, says Tarter, consumes about half the computing power of her institute's SETI research. That's a bit like your phone spending half its energy ignoring your neighbor's calls or text messages.
Astronomers who study natural phenomena, like clouds of space dust or dying stars, can ignore everything that looks artificial. But scientists looking for alien life can't do the same. The types of noises that are interfering with the search, says Siemion, are "exactly what we're looking for."
Which means impatiently waiting for a frozen dinner to heat up could potentially ruin our chance of finding another civilization.
'Delicate Creatures'
Not everyone, however, is convinced that the assumptions of radio astronomy make sense. Shelley Wright, an astrophysicist at the University of California, San Diego, is one of them. As she sees it, there's no knowing what technology another civilization might possess and what means it might use to say hello. "There's really no reason to think aliens would use radio over laser," says Wright, "over something else we haven't even invented yet."
Fiction has articulated the problem well. In Story of Your Life, for instance, an expert translator struggles to decipher an alien language (the 1998 novella was the basis for the movie Arrival). Or in Babel-17, a 1966 science fiction novel by Samuel R. Delaney, only a poet can understand an otherwise indecipherable message from another galaxy.
When it comes to hearing aliens, we may be victims of our assumptions about how they would talk to us. We tend to think of radio as the best means of communications because it was the first such technology that humans invented, says Wright. But with our most powerful technology, she says, we could theoretically pack all the internet's contents into a message sent tens of thousands of light-years away through a laser beam—which means another civilization could do the same
And so Wright and others are developing a new field of astronomy. It's called optical SETI, and its instruments are focused on a different band of the light spectrum than radio astronomy, looking instead at the same waves our eyes take in, along with infrared frequencies, which are just a smidge longer. It's also a technology we suspect aliens might use because humans have found it so powerful.
Wright is leading an optical SETI project to build a pair of observatories, faceted like giant soccer balls, in California. She hopes to turn prototypes on this year and to be watching the entire sky within six years. They will look for bright bursts of light, as if searching for a superpowered camera flash from an alien photographer.
But like radio astronomy, optical SETI isn't foolproof. It works only in dark and clear skies. The technology can also be overly sensitive—optical telescopes are "delicate creatures," says Paul Horowitz, a physicist at Harvard who is collaborating with Wright. The way to reduce false alarms is to use more than one instrument simultaneously. (Apparently, it takes at least two eyes to spot the alien in the room.) "Multiple observatories," Horowitz says, "are the only way to go for these things that go bump in the night and only rarely."
Then again, it's entirely possible that extraterrestrials have evolved beyond devices—or never created them in the first place.
Thousands of Planets
On April 8, 2009, NASA's satellite-based Kepler telescope delivered its first image. Scientists pointed the instrument at a patch of sky tucked under the wing of the Cygnus constellation, the swan that flies across the Milky Way. The goal: to find Earth-like planets.
Alone at the NASA Ames Research Center in Northern California that night, Natalie Batalha, an astrophysicist with the Kepler mission, watched the first image arrive on her computer monitor. She describes it like a champagne glass slowly filling with bubbles. When the picture was complete, Batalha saw immediately that Kepler had delivered a revelatory view of the universe. "It looked like you'd dumped a bunch of salt on black paper," she says, still in awe of the picture. "Just so many stars."
Since that moment, Kepler and other projects have revealed a new truth about the universe: It is unspeakably rich in planets. The tally climbs every week or two, with the current total nearing 4,000. This number alone boosts the hope of finding intelligent life. "When you realize that every pinpoint of light has a planet," she says, "you start to see the galaxy differently," says Batalha. "It would be foolish not to look."
These discoveries have completely reframed the odds behind the search for extraterrestrial intelligence. Those odds were outlined by Frank Drake, the father of modern SETI. He calculated the number of civilizations that could be sending us a signal right now by considering a string of variables: how often life-friendly stars are formed, the proportion of these that have orbiting planets and the fraction of these planets that are habitable, among other factors. The larger the numbers for all these components, the higher the chances of finding E.T. Even if every other variable stays the same, the number of planets we now know about changes the equation dramatically. Finding extraterrestrial intelligence may no longer be a question of "if" but rather one of "when."
So far, we are still waiting. A 72-second signal detected in 1977 generated brief excitement but was never heard again. Astronomers now think the noise was generated by gas from a comet. In the 16 years that physicist Gerry Harp has been hunting aliens at the SETI Institute, he says only one signal has looked promising, but that turned out to be from a satellite.
Likewise, the Green Bank Telescope's ultra-sensitive receptor found no trace of alien messages coming from 'Oumuamua. Loeb, the Harvard astronomer who led the investigation, says there's a chance the telescope could have missed a flickering signal. But the scientists weren't surprised by the noiselessness that followed.
Like many who devote their careers to listening for aliens, they are accustomed to radio silence.
With Jessica Wapner in New York
