Will Powerful New Tools Finally Let Us Hear Alien Civilizations?

These initiatives are collectively known as SETI, the Search for Extraterrestrial Intelligence. Its history dates back to 1960, when astronomer Frank Drake aimed an 85-foot antenna at two relatively close star systems, hoping to pick up an alien signal. It was a simple, two-week experiment using already-existing equipment. Although Drake failed to discover any transmissions, his work excited the public and spawned further attempts.

Early this year, the SETI Institute (where I work) and the University of California, Berkeley, launched COSMIC, a new project that is about a thousand times more comprehensive than Drake’s pioneering effort. It will search for alien signals—both intentional and unintentional—from some 40 million star systems by analyzing massive amounts of data from the Very Large Array, an ensemble of 27 antennas dotting the scrub deserts of western New Mexico. The researchers have also deployed cameras designed to look for powerful flashing lasers that could be used by extraterrestrials to beam information between star systems, much like a ship semaphore.

“COSMIC is a real game-changer in the field of searches for alien signals,” says Alex Pollak, the science and engineering manager at the Hat Creek Radio Observatory in northern California. “That’s because the array has the potential to observe more objects of interest than all other SETI searches combined.”

Looking for intentional electromagnetic transmissions assumes that aliens would be technologically advanced enough to send them and unafraid of revealing their presence by signaling. But even if aliens prefer to remain coy, there may be other ways to find them. One proposal is to look for the infrared light from so-called “Dyson spheres,” named for the British astrophysicist Freeman Dyson, who proposed that alien civilizations could put massive numbers of solar panels in orbit around a star to collect its energy. If such panels exist, they would radiate heat that might be visible to our telescopes. Several candidate sources have been found, but none has yet been confirmed as a Dyson sphere.

Another strategy is to search for civilizations that have the ability to re-engineer objects in space. Swedish astronomers have set up a simple but ingenious project that compares images of outer space taken dozens of years apart to see if anything has changed. This could reveal the existence of massive construction efforts. Another Swedish project, known as VASCO, looks closer to home, comparing images of our solar system taken before 1957 with recent photos of the same areas. Beatriz Villarroel of the Nordic Institute for Theoretical Physics calls VASCO “a straightforward attempt to find artificially constructed objects, including alien probes, that might be cruising our neighborhood.”

Is the idea of extraterrestrials just a pipe dream? The majority of scientists would answer no, based simply on the abundance of habitable real estate in the universe. There are at least 100 billion Earth-size planets in our galaxy, and telescopes have revealed several hundred billion other galaxies, each with a similarly staggering tally of worlds. Given these numbers, it’s difficult to argue that Earth is the sole place where intelligent beings strut and fret.

Nonetheless, we still haven’t detected a convincing alien signal. Does that buttress the belief that Homo sapiens is unique? The idea may be comforting, but there are myriad ways that alien societies could escape our notice. Perhaps we’re listening at the wrong radio frequencies, or our equipment is not yet sensitive enough to pick up transmissions from light years away, especially if they are just background noise. Alien civilizations might be hesitant to transmit detectable signals for fear of triggering an attack by aggressors. Absence of evidence isn’t evidence of absence.

If astronomers at COSMIC or elsewhere happen to find proof of extraterrestrial intelligence, the discovery would be a seminal event in human history. The public would clamor to know where the aliens are, what they look like and what their signals are saying.

Their location could be determined quickly, using traditional tools of astronomy. Other answers would depend on whether the aliens want us to understand them. If so, they could easily send picture dictionaries to allow us to carry on a long-distance “conversation.” Of course, the chat would be leisurely: Even if the aliens were as close to Earth as 50 light years away, each exchange would take a century.

Some earthlings might object that interplanetary colloquies would give away our existence and location, possibly exposing us to an existential threat. While it’s true that science fiction often pictures advanced beings as having outgrown aggression in favor of a peaceful way of life, would we want to risk the future of our species on this rosy hypothesis?

Such paranoia is silly, however. Radio, radar and television signals have been bubbling off our planet for more than a century, so if any aliens are paying attention, they could find us, just as we might find them the same way. It’s too late to worry about the security implications of interworld communication.

Given the immense distances that separate the stars, it’s doubtful that we will ever meet aliens face to face. Still, even if discovering their existence doesn’t affect us directly, it would change our worldview and that of all our descendants. We would know that life and intelligence have emerged elsewhere, and that despite being remarkable in many ways, Earth is not unique. COSMIC and similar efforts may yet turn out to be humanity’s most consequential project.

Dr. Shostak is the senior astronomer at the SETI Institute.