Should We Heed Stephen Hawking’s Warning About Extraterrestrials?

Renowned physicist Stephen Hawking has warned that reaching out to extraterrestrial beings might prove catastrophic. Yet, with cutting-edge, enormous telescopes, humanity is ramping up its efforts to locate them. Have we fully considered the risks?

In February 2008, NASA transmitted the Beatles track Across the Universe into deep space. Using the antennas of its Deep Space Network aimed at Polaris, the North Star, astronomers played a brief cosmic DJ set, hoping intelligent aliens might catch it during its 430-year voyage to that star.

The quest for intelligent life beyond Earth is a familiar theme in books and movies—but it’s also a real-world endeavor. NASA probes are scanning for planets beyond our solar system, while astronomers attentively monitor for any signals traveling through space. How incredible would it be to learn we’re not alone, to finally converse with an alien civilization? Wouldn’t it?

Not according to the esteemed Stephen Hawking. “If aliens visit us, the outcome would be much as when Columbus landed in America, which didn’t turn out well for the Native Americans,” Hawking remarked in an upcoming Discovery Channel documentary. He suggests that instead of seeking and communicating with cosmic life, humans should focus on avoiding contact altogether.

Hawking contends that, given the vast number of planets scientists believe exist, Earth is likely not the only home to life. After all, our galaxy alone contains billions upon billions of stars, with presumably even more planets orbiting them. It’s also plausible that some of that alien life is intelligent and able to communicate across interstellar distances. So, when someone with Hawking’s deep understanding of the universe advises against contact, it’s wise to pay attention, isn’t it?

Seth Shostak, a senior astronomer at the SETI Institute in California—the premier global organization hunting for alien signals—isn’t convinced. “This is an unwarranted fear,” Shostak says. “If their interest in our planet is for something valuable that our planet has to offer, there’s no particular reason to worry about them now. If they’re interested in resources, they have ways of finding rocky planets that don’t depend on whether we broadcast or not. They could have found us a billion years ago.”

If we were genuinely concerned about making noise in the cosmic jungle, Shostak argues, the first step would be to shut down the BBC, NBC, CBS, and all airport radars. Those transmissions have been leaking into space for decades—the earliest ones have already traveled over 80 light-years from Earth—so it’s too late to prevent passing aliens from watching every episode of Big Brother or What Katie and Peter Did Next.

The most extensive and active search for extraterrestrial life began in 1960, when Frank Drake aimed the Green Bank radio telescope in West Virginia at the star Tau Ceti. He was searching for unusual radio signals that might have originated from intelligent beings. This idea eventually evolved into SETI (Search for Extraterrestrial Intelligence), which used idle time on radio telescopes worldwide to scan the heavens for any signs. Yet, for 50 years, the skies have remained silent.

Of course, hunting for aliens comes with numerous practical hurdles, with distance being the most significant. If our closest neighbors were life-forms on the (fictional) forest moon of Endor, 1,000 light-years away, it would take a millennium for us to receive any message they might send. If the Endorians were observing us, the light reaching them from Earth right now would show our planet as it was 1,000 years ago; in Europe, that means knights clashing near castles, and in North America, small bands of natives roaming the great plains. This timescale doesn’t allow for quick conversation—and, besides, they might not be transmitting in our direction.

Despite the absence of a signal from ET, astronomers and biologists (not to mention filmmakers) have developed a wide array of ideas about what aliens might look like. In the early days of SETI, astronomers focused on finding planets similar to ours—the assumption being that, since Earth’s biology is the only one we know, aliens might resemble us. But there’s no reason that must hold true. You don’t even have to leave Earth to encounter life vastly different from our everyday experience.

“Extremophiles” are species that thrive in environments that would swiftly kill humans and other “normal” life-forms. These single-celled organisms have been discovered in boiling hot vents of water surging through the ocean floor, or at temperatures well below water’s freezing point. The front ends of some creatures living near deep-sea vents are 200°C hotter than their back ends.

“In our naive and parochial way, we have named these things extremophiles, which shows prejudice—we’re normal, everything else is extreme,” says Ian Stewart, a mathematician at Warwick University and author of What Does A Martian Look Like? “From the point of view of a creature that lives in boiling water, we’re extreme because we live in much milder temperatures. We’re at least as extreme compared to them as they are compared to us.”

On Earth, life exists in water and on land, but on a giant gas planet, for instance, it might float high in the atmosphere, capturing nutrients from the surrounding air. And given that aliens could be entirely beyond our experience, guessing their motives and intentions if they ever made contact seems beyond even Hawking’s capacity.

Paul Davies, an astrophysicist at Arizona State University and chair of SETI’s post-detection taskforce, argues that alien brains, with their different architecture, would interpret information very differently from ours. What we perceive as beautiful or friendly might appear violent to them, or vice versa. “Lots of people think that because they would be so wise and knowledgeable, they would be peaceful,” adds Stewart. “I don’t think you can assume that. I don’t think you can put human views on to them; that’s a dangerous way of thinking. Aliens are alien. If they exist at all, we cannot assume they’re like us.”

Answers to some of these puzzles will start to emerge in the coming decades. Leading this work are astrobiologists, operating in a field that has steadily moved from the fringes of science thanks to advances in space exploration technology.

Scientists identified the first few extrasolar planets in the early 1990s, and the count has skyrocketed since then. Today, scientists know of 443 planets orbiting more than 350 stars. Most are gas giants similar to Jupiter, with the smallest being Gliese 581, which has a mass of 1.9 Earths. In 2009, NASA launched the Kepler satellite, a probe specifically designed to search for Earth-like planets.

Future ground-based telescopes, like the proposed European Extremely Large Telescope (with a 30-meter main mirror), could be operational by 2030 and would be powerful enough to image the atmospheres of distant planets, looking for chemical signatures that might indicate life. The SETI Institute is also finally building a serious piece of equipment: the Allen Array (funded by a $11.5 million/£7.5 million donation from Microsoft co-founder Paul Allen) currently has 42 radio antennae, each six meters in diameter, but there are plans, if the SETI Institute can raise another $35 million, to expand to up to 300 radio dishes.

In all the years SETI has been active, it has thoroughly examined fewer than 1,000 star systems. With the full Allen Array, they could survey 1,000 star systems in just a couple of years.

Shostak is confident that, as telescope technology continues to improve, SETI will detect an ET signal within the next two decades. “We will have looked at another million star systems in two dozen years. If this is going to work, it will work soon.”

And what happens if and when we detect a signal? “My strenuous advice will be that the coordinates of the transmitting entity should be kept confidential, until the world community has had a chance to evaluate what it’s dealing with,” Davies recently told the Guardian. “We don’t want anybody just turning a radio telescope on the sky and sending their own messages to the source.”

But his colleague, Shostak, says we should have no such concerns. “You’ll have told the astronomical community—that’s thousands of people. Are you going to ask them all not to tell anybody where you’re pointing your antenna? There’s no way you could do that.

“And anyway, why wouldn’t you tell them where [the alien lifeform] is? Are you afraid people will broadcast their own message? They might do that but, remember, The Gong Show has already been broadcast for years.” And, for that matter, the Beatles.