Some of the 27 dishes that are part of the Very Large Array, in New Mexico. ( Alex Briseño/Flickr)
Some of the 27 dishes that are part of the Very Large Array, in New Mexico. ( Alex Briseño/Flickr)

The Best Way to Eavesdrop on Aliens

This is one of three blog posts associated with this week’s episode of Cosmos: A Spacetime Odyssey, which addresses life in the universe. Watch it Mondays on the National Geographic Channel.

Though humanity’s origins are humble, our dreams are grand.

It took millennia for our ancestors to leave their watery cradles. But from those primordial ponds, they eventually emerged and pressed their footprints into land. Those footprints would march through the eons, marking an inexorable progression toward the hairy, bipedal, big-brained beings we are today.

In just a fraction of the time it took those quivering creatures to evolve the lungs needed to breathe Earth’s freshly oxygenated air, our empires have risen and fallen, ideas have wrought the deaths of millions and humans have become an interstellar species.

It wasn’t until 1937 that the first powerful FM transmitter was built and began transmissions at a frequency that could fly into outer space. Those early signals, along with the crude chirps of World War II radars, the first moon bounce of 1946, and all of our TV broadcasts have been zooming into the cosmos for many decades, travelling at the speed of light.

“The leading edge of these signals has already washed over thousands of planets of other stars,” says Neil DeGrasse Tyson, in this week’s episode of Cosmos: A Spacetime Odyssey. “What if other worlds are sending their stories into space? Since 1960, we’ve been listening for extraterrestrial radio signals, without hearing so much as a tolling bell. But our search has been sporadic and limited to small parts of the sky. For all we know, we may have just missed an alien signal, looking in the wrong place at the wrong time.”

It’s a plausible and disheartening reality.

My first story for this blog was about the 1960 search Tyson references, called Project Ozma. Conducted at the Green Bank Observatory in West Virginia, by my father, Frank Drake, the search targeted just two stars. For three months, those stars refused to be anything but quiet. But scientists didn’t quit – in fact, Project Ozma launched an era of listening to the cosmos. Over the last half-century, more than a hundred such searches for extraterrestrial intelligence have been conducted – and all have been met with that same stubborn silence.

One obvious explanation is that humans are alone, that we are the only species in the galaxy to have slipped the surly bonds of single-celled solitude and begun broadcasting our stories into space.

But it’s much too early to conclude that.  A realistic explanation is that our searches haven’t been good enough. Tyson is right: They’ve been sporadic and limited in scope.

So if aiming the world’s largest single-dish radio telescope at the stars, or harnessing the computer power of a thousand idle PCs isn’t enough, then what is?

“You need to look at many stars, you need to look almost continuously, and you need to cover a large piece of the radio spectrum,” Dad said, when I asked what his ideal, Earth-based SETI search would be. “If you want to build just one system to do this, you have to put it very near the equator. It’s the only way you can look at the whole sky, every day.” (Better still, he says, would be to have two telescopes placed opposite one another along any line through the center of the Earth — you could monitor the entire sky continuously.)

Dad describes his ideal telescope as comprising a square kilometer radio telescope – kind of like the planned Square Kilometer Array – but with many dishes arranged in a single, dense cluster. Positioning the dishes close together is essential for observing the largest possible number of stars at the same time, which is important for SETI searches. “The game is to look at as many stars as possible since we don’t really have a clue as to which are the best candidates,” he says.

But if you’re looking at 1,000 stars at once, I ask, how will you know which star a signal might come from? “We would love to have that problem,” came the wry response. Turns out, by paying close attention to how the signal shifts in frequency as the Earth rotates, you can figure out which is your lucky star.

“The technology to do this actually exists,” Dad says. “It doesn’t require new inventions.”

A giant telescope, parked on Earth’s equator like a shiny badge, staring into the sky day and night? Sounds pretty good. But the challenges are enormous. The good news is, none are insurmountable. The computing power needed to synchronize incoming data and then process those data, plus the costs of electricity, construction, and management – none of that is negligible. Dad’s figured out how to make most of these things work. The bad news is, as always, cost – possibly as much as $20 billion.

In this age where the U.S. government is nickel-and-diming programs and struggling to scrape together even a tenth of that number for a single solar system mission, $20 billion is enormous. But this is also an age where a 10-year-old Internet company paid $19 billion for an instant-messaging app. For roughly the same price, we could instant-message the cosmos.

How long would it take for such a telescope to find a signal? That’s another question Dad gets a lot, apparently. “You have to make two guesses,” he says. “One is the answer to the Drake Equation [which estimates the number of detectable civilizations in our galaxy], and the other is, how often do they actually send a message our way? There’s no logic I know of that can answer that second thing.”

It could be days, it could be weeks, it could be never.

Whether Earth is the only fertile planet is a question I grew up thinking about, surrounded by replicas of the Pioneer plaque and instruments meant to bring the stars the closer to Earth.

Surely there’s another species out there that has clawed its way from oozing, primordial murk and evolved through eons of uncertainty and shifting skies and become aware of the questions posed by the stars. Perhaps these are the same beings that are now decoding the transmissions from Earth that are streaming across the light-years.

“I am sure they are out there,” dad says.