Are we alone? Institute searching for alien signals is using a new way to answer that age-old question

In case you didn’t know, the search for life — specifically intelligent life — has been ongoing for decades. But so far, it’s just us.

Astronomers look for life in two ways: searching for biosignatures, evidence of past or current biological processes (think Mars rovers); and technosignatures, evidence of technology created by an intelligent civilization. Looking for the latter primarily involves radio astronomy, not optical, because any activity would be happening too far away for us it see it. Basically, astronomers are listening for something.

One of the organizations at the forefront of that has been the SETI Institute. Since its founding in 1984, it has scanned the sky for radio signals that might be crossing the great cosmos just to say “hello” to us humble earthlings. It’s pointed at star systems with known exoplanets, but so far, no signals from ET have been detected.

But now, scientists at the organization, based out of Mountain View, Calif., have come up with a novel method to look for these signals, incorporating game theory. Not only does this method look at where we should be searching for these signals, but also when.

Game theory is a branch of mathematics that studies interactive decision-making, where there is an interdependence between the two “players” or “agents.” Each player considers the other player’s strategy while not knowing what the other is doing. The winner depends on the collective strategy.

WATCH | Game theory explained:

In the case of the SETI Institute, it is using the “Schelling point” of game theory. The example most cited by American economist Thomas Schelling is this: Imagine you’re meeting someone in New York City, but you haven’t communicated a time or place. Both of you might choose to go to Grand Central Terminal at noon, as it’s a common meeting place and a reasonable time.

Now apply that to listening for an alien civilization, and consider the anti-solar point, an imaginary spot on the celestial sphere that is opposite the sun (180 degrees away). Think of a straight line from the sun that passes through Earth out into space.

What if there was an alien civilization that could see Earth cross in front of the sun, which is called a transit? What if they knew there was a planet around our particular star and they sent a signal toward us? 

We have the where — Earth — and the when — during a transit.

Basically, we're meeting at Grand Central at noon.

Voices in the void

This anti-solar method had been suggested years ago, but there wasn’t enough funding to attempt it until now.

“I thought about these ideas that have been percolating for a long time in the literature,” said Sophia Sheikh, technosignature research scientist at the SETI Institute, and lead author of the paper. “And so now the anti-solar point idea is sort of finally getting its time in the sun.”

In their new paper released Nov. 3, SETI Institute astronomers reported that they detected 1.9 million radio signals using this method. However, after filtering them all out, they did not detect any that matched extraterrestrial technology — the signals were all us. It turns out that we earthlings, with our satellites and radio transmissions, are pretty loud.

The study ruled out that small part of the sky — but that doesn’t mean that there’s nothing out there. Space is pretty big.

So they plan on continuing this method to search for at least four years, said Sophia Sheikh, technosignature research scientist at the SETI Institute, and lead author of the paper.

The Sun and our solar system in relation to the Milky Way galaxy. The white circle indicates the area where the majority of exoplanets have been found with current telescopes. (NASA/JPL-Caltech/T. Pyle)

They're looking for something called a narrowband signal, said Sheikh, who described it as a "'we are here' ... like an air horn, almost, in the radio frequencies." 

“Maybe there is information contained in it, or maybe the signal that we find is what we'd call a carrier wave. So the air horn, that says, 'Hey, there's something interesting here.'"

But don’t think of astronomers sitting with headphones on, like Ellie Arroway in 1997's Contact. Instead, computer programs sift through the data.

The SETI Institute is using the Allen Telescope Array, a collection of 42 fully steerable 6.1m-diameter telescopes at the Hat Creek Radio Observatory in California — which has been used to look for alien signals since the 1980s — to do the search.

Pictured here is the Allen Telescope Array, the first radio telescope built specifically for searching for extraterrestrial intelligence (SETI). Located at the Hat Creek Radio Observatory in northern California, it features 42 antennas. (Simon Steel)

Science fiction?

Searching for extraterrestrial signals may seem like something out of science fiction. But with our Milky Way galaxy holding 100 billion stars or more, there’s a belief that there ought to be someone out there, especially considering that we now know that most stars contain at least one exoplanet.

Then there’s the Drake equation, devised by American astrophysicist Frank Drake in 1961. His aim was to estimate the number of potentially communicative civilizations in the Milky Way. 

The answer is dependent on many unknown variables, but it's not zero.

Adam Frank, professor of astrophysics at the University of Rochester in New York, is also searching for technosignatures. He was awarded NASA’s first grant to study non-radio technosignatures. Instead, he looks at the chemical signatures or other indicators of an intelligent civilization.

He's talked about how the search for extraterrestrial intelligence wasn't taken seriously in the past.

“The giggle factor, which existed through almost my entire career, is gone," said Frank, referring to the fact that the possibility wasn't taken seriously decades ago. "And it never made sense."

That's particularly true after the first discovery of exoplanets in 1992, and the first discovery of an exoplanet around an sun-like star in 1995.

In the event of a detection...

Let’s say there was a detection. What then?

Believe it or not, there are protocols in place set out by the International Academy of Astronautics. Aside from the obvious — confirming and authenticating the finding — there’s a pretty big one: Do not answer. (If you've read or watched 3 Body Problem by Lui Cixin, you'll understand why that's probably a good protocol.)

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Turns out that’s not exactly a major issue. Signals will be crossing distances of light-years. So, imagine we receive a signal from a star system that is 100 light-years away, and we on Earth agreed to send a response. It would take 100 years for our signal to get to the alien civilization, and then another 100 to receive their response. That’s 300 years just to say, “Hey.”

"Communication is not Job 1," Frank said.

Frank’s research involves searching for evidence of technosignatures by studying an exoplanet’s chemistry.

“For example, we can look in the atmospheres of alien planets and we could look for something like chlorofluorocarbons ... a chemical that only industry produces,” he said. "You'll never get it from just nature, from a biosphere.”

So it will be more about taking comfort knowing that we’re not alone.

This image shows the printout of a strong signal received at the Big Ear Radio Observatory in 1977. Astronomer Jerry Ehman circled the unusual signal and wrote, 'Wow!' in the margin. (Big Ear Radio Observatory and North American Astrophysical Observatory)

While we haven’t detected a definitive radio signature that might indicate an alien civilization, there was the famous “Wow! Signal.” This powerful radio signal was detected in 1977 by the Big Ear telescope in Ohio. It lasted for 72 seconds but was never detected again. Since then, there has been some speculation that it was the result of passing comets.

So when could we detect an alien signal?

"The thing I like to say," said Sheikh, "is I hope that by the end of my career, we have a sense of whether there are any radio signals in the galaxy being produced by other technology-having civilizations."