Is SETI Hopeless?

by Seth Shostak, SETI Institute
Dec. 03, 2009

Ben Zuckerman thinks that SETI’s chance of turning up extraterrestrials is comparable to the likelihood you’ll strike oil in your front yard. In other words, he doesn’t give the experiment much hope.

Back in the day, Zuckerman was more sanguine about the Search for Extraterrestrial Intelligence. As a student at Harvard, he had an office down the hall from Carl Sagan, a bit of geographic felicity that soon led him to become intrigued by the then-new idea of discovering the aliens with an antenna and some patience. A few years later, he and another astronomer, Pat Palmer, tried out this idea by aiming the now-departed 300 foot radio telescope in West Virginia at a few hundred close-by star systems. It was one of the earliest SETI experiments, and the two astronomers called it Ozma II in homage to SETI’s pioneering search, Project Ozma.

Ozma II didn’t find anything. Today, Zuckerman believes it was doomed from the get-go. Why? Well, his reasoning goes like this:

Imagine yourself as an alien (perhaps you already feel this way) on a planet within a few hundred light-years of Earth. Sometime during the technical heyday of your society, you develop telescopes able to image planets around other stars and – even better – spectrally analyze their light. At some point, you’ll notice that our world’s atmosphere is laced with such uncommon, but telltale ingredients as oxygen and methane. In other words, you’ll discover that Earth is blessed with biology (a discovery that will no doubt garner you tenure at Klingon U).

Having established our planet’s fecundity, you – as an inquisitive alien – will mount a SETI experiment in the hope of uncovering, not just life, but intelligent life. You’ll turn some antennas towards Terra Firma.

As it turns out, doing so will probably prove more frustrating than an itch in the small of the back. After all, Earth has had oxygen in its atmosphere for two billion years, but it’s only boasted radio transmitters for less than a century. The chances you’d tune in a terrestrial Top Forty station are not exactly high.

But let’s assume that funding holds up, and you keep your alien antennas trained on Earth for hundreds or even thousands of years. Most probably, you’d still fail to hear anything.

“At this point,” avers Zuckerman (now a professor of astronomy at UCLA), “you’d resign yourself to admitting that ‘OK, it’s life. Just not broadcasting life.’”

But that would be cold comfort. After all, you and your alien pals couldn’t learn all you wanted to know about Earth’s biology from spectroscopic data alone. For example, do any of our world’s organisms sport fur, feathers, or four legs? Do our flora and fauna include bugs and bipeds? Indeed, are there fauna at all? All good and interesting questions that, according to Zuckerman will surely pique the interest of an advanced civilization.

In other words, aliens would surely wish to know more about life on Earth than simply the fact that it has a few, easily detectable exhaust gases.

The quest to learn the answers will inevitably drive the aliens to the point of organizing a visit to Earth, either in person or by a proxy probe. And yes, that exploratory craft might take a long time to get here, but so what? The aliens have the choice of doing SETI for millions of years with only a small chance of hearing anything or – they could send a rocket. At least by doing the latter, their biologists will eventually have some real meat to work with – or at least some pictures of meat.

Having spun the story thus far, Zuckerman now takes it home – bringing it to what he believes is its obvious, if disheartening, conclusion.

“We don’t see any extraterrestrial probes here,” he says. “There’s no evidence that Earth has ever been visited.”

Bottom line: You can rule out aliens in the hood. They’re not there, because they’re not here. And their reconnaissance hardware’s not here either.

Call it a local variant of the Fermi Paradox. Call it speculation on alien sociology. Or call it just a bit too anthropocentric.

Ben Zuckerman calls it something else: an argument worth considering.

And I will consider it – in my next column. As we say here at the SETI Institute, stay tuned.

Shostak is the author of “Confessions of an Alien Hunter”