Fifty years ago this week, a young Cornell University scientist named Frank Drake pointed a radio telescope at a distant star, hoping to hear transmissions from an alien civilization.
After a half-century, the search for extra-terrestrial intelligence, or SETI, has pretty much come up empty. But a leader in the SETI community says maybe we're looking in the wrong way.
When the search began, a half-century ago, it seemed sensible to assume that as technological civilization increased on a planet, more and more signals would be broadcast into space. It was just a matter of knowing where and how to tune in.
Now, it seems sensible to assume that that assumption could be wrong. Television and radio transmitters on Earth may soon go dark, replaced by cable, fiber, satellites, and the Internet.
So Arizona State University physicist and astrobiologist Paul Davies says we might not be hearing alien civilizations because they have transcended their broadcasting stage. And, as for sending a message aimed at us, Davies says they probably don't even know we're here.
'10,000 communicating civilizations in the galaxy'
"Even an optimist like Frank Drake estimates that there would be no more than about 10,000 communicating civilizations in the galaxy, which means that the nearest one is likely to be about 1,000 light years away," he said in a VOA interview.
"Now, if you're on a star about 1,000 light years away, you see earth as it was 1,000 years ago. There were no radio telescopes. There was no radio technology here. It would make no point in those aliens sending messages our way at this particular time."
Davies is the author of a new book, "The Eerie Silence," which reviews the search for alien life and suggests ways to broaden the quest.
He's not against the radio telescope surveys that have been the mainstay of SETI for the past 50 years, but he says maybe we're looking for the wrong thing.
"We could look for beacons," he suggests. "It could be that there are alien civilizations that have simply created something a little bit like a lighthouse that sweeps the plane of the galaxy, goes bleep, and it's there to attract attention, or it's a monument, or an aesthetic symbol or even a religious symbol. Who knows? And that's a different type of search. I'm trying to urge the SETI community to change their tactics a bit."
Or maybe, instead of a radio signal, an alien civilization sent us something physical. Science fiction writer Arthur C. Clarke described an object left on the moon to let aliens know when humans were able to travel in space. Davies says maybe aliens have sent a probe to orbit the Sun.
A more intriguing possibility is that our genetic makeup includes a signal encoded by aliens in our DNA that might have been left hundreds of millions of years ago.
"We have genes inside our body that go back three billion years, largely unchanged. So if you can somehow upload a message into DNA of terrestrial organisms, it could last a very, very long time, indeed."
Paul Davies admits some of his ideas may be "fanciful."
"But they illustrate what I want to try to do in this book, which is to just broaden the thinking to get away from this traditional sort of radio search. That should carry on, of course. But in addition, we need some new thinking. After 50 years of silence, I think the time has come to take stock and say, maybe we should mobilize all of the sciences to look for anything fishy, anything weird, any anomaly, both in our own little corner of the universe here on Earth and in the solar system, and far out across the galaxy."
University of Arizona scientist Paul Davies' new book, "The Eerie Silence," advocates an expanded search for extra-terrestrial intelligence.