It may not be common knowledge on Earth, but the search for intelligent life elsewhere in the universe is heating up—and so is the debate about how to do it.

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Remember those “alien megastructures” scientists tossed out as one theory for why a certain star in our galaxy was dimming so dramatically? According to research released last month, it may be too early to rule them out. The Strange Case Of KIC 8462852 In October last year, the Atlantic reported that astronomers had noticed a sharp decline in the amount of light emitted by a star called KIC 8462852, or “Tabby’s star,” after Tabetha Boyajian, the Yale researcher who’d first noticed the pattern in data collected by the Kepler Space Telescope. It looked as though something was passing in front of it—something big. There were no obvious culprits, natural or otherwise, so some experts surmised that the big something might be enormous contraptions built by a distant civilization to harvest the star’s energy, known in the trade as a Dyson swarm. Others argued that a very large cloud of comets might be a better explanation. This illustration shows a star behind a shattered comet. Observations of the star KIC 8462852 by NASA’s Kepler and Spitzer space telescopes suggest that its unusual light signals are likely from dusty comet fragments, which blocked the light of the star as they passed in front of it in 2011 and 2013. Image: NASA/JPL-Caltech And that, scientifically speaking, was that—until a few weeks ago, when the astronomer Bradley Schaefer compared the Kepler data with roughly a century’s worth of earlier observations and ruled comets out. “The comet-family idea was reasonably put forth as the best of the proposals,” Schaefer told New Scientist in January. “But now we have a refutation of the idea, and indeed, of all published ideas.” Extraterrestrials were, however dimly, still plausible. Why Aliens? Why Not? Since the ideas most of us entertain about aliens are indebted to The X-Files and the types of people who show up in Discovery Channel specials, it’s easy to have not paid attention to real research showing that the probability aliens actually exist has multiplied in recent years.

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“When I was a kid and you asked astronomers what fraction of stars had planets where there could be life,” Seth Shostak, a senior astronomer at the SETI Institute in Mountain View, California, tells Fast Company, “they’d say, ‘Well, maybe one in a million.’” Today, “the answer seems to be maybe 5 percent, maybe 10, maybe 20″—about “as common,” cosmologically, “as cheap motels.” We know that largely thanks to the Kepler telescope, which launched in 2009 to search for “exoplanets,” those planetary bodies whose size and distance from their stars make them capable of sustaining life. The Kepler telescope’s full field of view. A cluster of stars, called NGC 6791, and a star with a known planet, called TrES-2, are outlined. The cluster is eight billion years old, and located 13,000 light-years from Earth. Image: NASA/Ames/JPL-Caltech Almost immediately, says Douglas Vakoch, a colleague of Shostak’s at the SETI Institute, “Kepler revolutionized SETI”—shorthand for the “search for extraterrestrial intelligence”—because “it is able to detect these minute dimming patterns that you just can’t detect when you’re looking through the atmosphere of Earth.” If a star gets dimmer at regular intervals, chances are a planet is orbiting it, periodically blocking its light. One of Kepler’s parts broke in 2013, but scientists managed to keep the telescope in use despite diminished precision. During that second phase alone, called “K2,” it’s identified over 200 confirmed exoplanets, for a grand total of 1,918 to date, plus more than 4,600 unconfirmed contenders, all in just one narrow slice of sky. Scientists have debated for years why we haven’t found clear proof of intelligent life given the likelihood that it exists, with answers ranging from the mathematical and philosophical to the bizarre. Kepler’s discoveries hint that they may just be technological. That’s recast another question once considered hypothetical as a practical one: If we just about know there’s life out there, what’s the right way to look for it? Expanding The Search Douglas Vakoch Photo: via SETI Institute At the SETI Institute, Vakoch is the director of Interstellar Message Composition, which puts him in charge of an initiative that the organization has largely avoided until recently. He’s also the president of METI International, which he helped set up last July to “conduct scientific research and educational programs in Messaging Extraterrestrial Intelligence (METI).”

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It was the culmination of years of heated dispute over the wisdom of trying to make contact with extraterrestrials, also called “active SETI,” which some in the field think is a waste of time and others consider an existential threat to humanity. Stephen Hawking, for one, has wagered that advanced life-forms might not have the friendliest intentions and “may not see us as any more valuable than we see bacteria.” In February last year, 28 leading astronomers signed a statement warning of METI’s dangers. Seth Shostak Photo: via SETI Institute Shostak and Vakoch agree that most of those fears are overblown, but it’s Vakoch who appears more concerned that they’re stymying worthwhile research. “People have gotten bogged down in details that they really haven’t evaluated,” he says, pointing out that it “doesn’t make a lot of sense” for aliens to “travel across interstellar distances and strip-mine our Earth for resources,” referring to one of Hawking’s concerns. In Vakoch’s view, the major SETI organizations are searching with just a flashlight in one hand when we need to put a megaphone in the other. While METI is an “innovative alternative,” he says the two methods aren’t mutually exclusive: “To me it’s a reflection of the natural growth that you see in the science,” and with METI International, Vakoch is aiming “to get prepared for the long run.” More Eyes On The Sky Which brings us back to whatever’s going on at KIC 8462852, which has been the subject of an unusually wide range of investigations, some technological and some human. For two weeks last fall, the SETI Institute trained the Allen Telescope Array in Mountain View on it in order to listen for radio signals at the same time that the Boquete Optical SETI Observatory in Panama looked for laser pulses. It was the first time the Allen Array had been used to search for relatively wide-band emissions, not to mention one of the most international and collaborative SETI research projects ever. The Allen Telescope Array Photo: Seth Shostak via SETI Institute Right from the beginning, both Shostak and Vakoch have doubted the “alien megastructures” hypothesis, and neither are surprised they didn’t find anything. “Even if there were a lot of transmitters on that star,” Shostak muses, “there would have to be a lot of them aimed our way” to pick them up, to name just one of many reasons in favor of a natural explanation. For both astronomers, the bigger lessons are about what we can learn by testing the ET hypothesis anyway. “Finding planets is something nobody had done 20 years ago,” Shostak says. As soon as Kepler started coughing up exoplanets left and right, “it became one of the most interesting projects in astronomy. There’s now an army of people doing it.”

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METI International is designed to keep them forward-looking as productively as possible, now that we can expect to find many more exoplanets and oddities like Tabby’s star in the years ahead. In that sense, the exigencies of SETI research are making astronomy more global and vice versa: since stars set, you need a network of observatories around the world to monitor them continuously. And then you need people. Telescopes can spit out tons of data, which creates plenty of work for citizen scientists to join astronomers in sifting through it all. According to Vakoch, Kepler didn’t automatically detect Tabby’s star’s weird dimming at first; it was caught by “human beings who were eyeballing the data and saying, ‘Hey, I see this strange glitch here.'” Eyeballs won’t be in short supply. What will soon be the world’s largest radio telescope is now rising in Guizhou, China, and last summer the SETI Institute landed $100 million in new funding from a Russian venture capitalist. As the search for alien life expands, Vakoch is gearing up for more disagreement over METI’s place in it: “I expect the debate will intensify.” How can it not? In Paradise Lost, the angel Raphael warns Adam, “Dream not of other Worlds, what Creatures there / Live, in what state, condition, or degree.” We know how that went.