Active SETI: Should we reach out to extraterrestrial life, or are aliens dangerous?

It Could Be a Really Bad Idea for Us to Contact Aliens

It Could Be a Really Bad Idea for Us to Contact Aliens

The citizen’s guide to the future.
March 29 2015 6:39 PM

Is This Thing On?

The fierce debate over whether we should try to contact extraterrestrial life or wait for aliens to contact us.

Littler Green Men
Earth to the Toy Story aliens. Do you read us?

Photo by JD Hancock/Flickr

This article is part of Future Tense, a collaboration among Arizona State University, New America, and Slate. Future Tense explores the ways emerging technologies affect society, policy, and culture. On Thursday, April 9, Future Tense will host an event in Washington, D.C., on the future of space exploration. For more information and to RSVP, visit the New America website.

It’s been more than 50 years since astronomers carried out the first systematic attempt to hunt for radio signals from civilizations beyond our solar system—a quest known as the Search for Extraterrestrial Intelligence, or SETI. During that time, our telescopes have heard only deafening silence—which has some scientists wondering if it’s time for Earthlings to start the conversation.

Proponents of “Active SETI” believe that, instead of just passively listening for signs of extraterrestrial intelligence, we should be actively reaching out to our galactic neighbors—that is, we should be using our most powerful radio transmitters (like the giant dish-telescope at Arecibo, in Puerto Rico) to send messages in the direction of the nearest stars.


“In the past we’ve always assumed that any extraterrestrial civilization with the capacity to detect us will automatically take the initiative to make contact, sending us a powerful signal to let us know they exist,” says Douglas Vakoch of the SETI Institute in Mountain View, California, and a leading proponent of Active SETI. “But there may be civilizations out there that refuse to reveal their existence unless we make it clear that we want to make contact.”

Active SETI has always been a contentious issue. Back in 2006 the International Academy of Astronautics convened a committee on SETI—but when the group refused to push for a ban on proactive transmissions, two prominent members, John Billingham and Michael Michaud, resigned. Even the editorial board of the prestigious journal Nature has cautioned that “the risk posed by active SETI is real. … It is not obvious that all extraterrestrial civilizations will be benign—or that contact with even a benign one would not have serious repercussions for people here on Earth.”

The debate reignited in February at the annual meeting of the American Association for the Advancement of Science, held in San Jose. Vakoch arranged for a symposium as well as a press briefing to discuss Active SETI at the conference; later that week, he convened an all-day workshop at the institute—and once again the discussion was heated.

What everyone agrees on—and it’s just about the only thing they agree on—is that any alien civilizations we find are likely to be much more advanced than our own. (It’s a simple matter of statistics: We’re only a few hundred years old as an advanced industrial species, while the galaxy has been here for some 13 billion years; any ETs we encounter are sure to be a lot older than us, and thus, presumably, a lot more advanced.) Fancier technology, greater risk.


Science fiction writer David Brin is an outspoken critic of Active SETI. He points to the history of our own planet, in which encounters between cultures of greatly differing technological sophistication rarely go well. “We have many examples where a technologically advanced civilization contacted a technologically less advanced civilization,” he says. (European colonizing efforts in Africa and the Americas come to mind.) “And in every one of those cases, there was pain. Even when both sides had the best of intentions.”

This pattern, Brin says, applies even when human beings aren’t involved. When plate tectonics brought the land masses that we now call North and South America together, about 3 million years ago, it enabled contact between the placental mammals of the north and the marsupial mammals of the south. “Within a million years, almost all of the marsupial mammals were extinct,” Brin says. “Contact between biomes had major extinction consequences every time it happened on Earth. I’m not claiming this is how things will go when we meet aliens—but it suggests that we should at least talk it over first.”

SETI pioneer Jill Tarter, the astronomer who famously served as the model for the main character in Carl Sagan’s Contact, agrees that it’s prudent to listen before we shout. “We should recognize that asymmetry [in technological sophistication], and allow the older technologies to take on the greater burden of transmitting,” she says. “We should listen, first, as youngsters.”

Unless Vakoch is right, and they are waiting to hear from us. If that’s the case, and we choose to remain silent, we’re squandering an incredible opportunity. “Perhaps interstellar communication is a form of economic exchange, where civilizations share valuable information with one another in a multigenerational form of reciprocal altruism,” he says, adding that examples of this sort of altruism can be seen in a variety of animal species here on Earth.


Seth Shostak, the institute’s wisecracking, mop-topped senior astronomer, agrees that we have little to lose, and possibly much to gain, by reaching out. Besides, they probably already know we’re here: Our radio and television broadcasts, and especially our military radar, have been leaking into space for some 70 years, Shostak points out. There’s no putting the electromagnetic cat back in the bag.

“Any society that’s at least 100 or 200 years more advanced than we are will be able to pick up our leakage,” says Shostak. “Unless they’ve stopped developing technology—which is of course possible, but then they’re of no threat to us.” (Shostak’s license plate, incidentally, reads SETI GUY; Vakoch has the more cryptic ASETI, for Active SETI.)

But maybe we haven’t yet blown our cover: Brin doesn’t accept Shostak’s assertion that “they” already know we’re here (sometimes called the “barn door” issue). Shostak is too generous in calculating how visible we are from hundreds (or even thousands) of light-years away, says Brin, who holds a Ph.D. in planetary science and has done consulting work for NASA. Terrestrial radio and TV signals, from I Love Lucy to whatever is leaking out of Vandenberg and Guantánamo, are relatively weak. Furthermore, electromagnetic signals fall off in proportion to the square of the distance (and ETs, if they exist, are pretty darn distant). Most likely, Brin says, they have no idea we’re here—and they won’t, unless we start beaming powerful, highly directed signals in the manner that Vakoch proposes. (The few physical-artifact messages that we’ve sent—on the Pioneer and Voyager probes, for example—are long shots in the extreme. They contain basic information about humans and our planet; on Voyager, there was also a gold record with music ranging from Mozart to Chuck Berry, and other greetings from Earthlings. They’re not heading for any particular star, and thus may never be intercepted at all—but Voyager 1 will be within two light-years of a star called Gliese 445 in about 40,000 years.)

Brin isn’t alone in urging caution. More than two dozen scientists have signed a position statement calling for a moratorium on Active SETI until “a worldwide scientific, political and humanitarian discussion” has taken place. Elon Musk, the billionaire founder of SpaceX, has signed on; so too have planet hunter Geoff Marcy and best-selling science author Paul Davies. The petition doesn’t say anything about ravenous, drooling aliens—it merely notes that “it is impossible to predict whether [extraterrestrial intelligence] will be benign or hostile.” But some, like renowned cosmologist Stephen Hawking, have been more direct. Hawking recently warned that an advanced alien civilization, having depleted the resources of its home planet, might be “looking to conquer and colonize whatever planets they can reach.” He also cited the analogy of Christopher Columbus arriving in the Americas, “which didn’t turn out well for the Native Americans.”


Clichéd as it may be, the oft-repeated Columbus analogy sometimes feels as though it has the power to sink Active SETI. It is, however, a gross oversimplification of human history. Kathryn Denning, an anthropologist at York University in Toronto, points out that not all cross-cultural contact has been harmful. Even the European arrival in the Americans wasn’t all bad. “Many of the First Nations of the New World are very much alive, and on the ascendancy, [especially] in the Southern Hemisphere,” she told me recently. Yes, there was a period of turmoil; but later there was “syncretism, friendship, intermarriage … a slow merging of two societies.”

Will ETs be friendly teachers or despotic overlords? Will we be their pupils, or their lunch? For an endeavor that purports to be rooted in science, much of what SETI enthusiasts have to say seems to hinge on whether they grew up with the death-ray-wielding invaders of The War of the Worlds, or the benevolent brainiacs of Contact.

For optimists like Vakoch, the mere possibility that ET might be benevolent is enough to justify reaching out. Making contact would provide, at the very least, “a unique opportunity to hold a mirror up to ourselves—to understand how much about our human way of experiencing the world is unique to our species, and how much taps into a more universal way of understanding.” Are math and science universal, or mere human constructs? What about ethics? With contact, at last we would know. “We might learn about alien culture, art, and music,” says Vakoch. But even more importantly, deciding what we wanted to say would have an immediate payoff (a sentiment that even Brin agrees with). Pondering what we want to say about ourselves to another civilization, he says, would force us to think about our most basic values.

“We sometimes talk about SETI as an attempt to join the galactic club,” Vakoch says. “But I never hear anyone talking about paying our dues—or even submitting an application. That’s what Active SETI is. And it may just be the approach that helps us make contact with another world.”