Is Anybody Out There?

Nestled in a remote ridge in Northern California, silvery sentinel radio telescopes are tilted to the heavens like huge high-tech ears. TheyÂ're listening intently for signs from distant worlds.

CBS News Sunday Morning Correspondent Bill Whitaker visited the Hat Creek Radio Observatory to meet people who have devoted their lives to answering the age-old cosmic question: Are we alone?

"In the galaxy, in the Milky Way, everywhere. And for all of us it was kind of a big moment," says Welch. "If this stuff can form these dense dust clouds out there, which is where stars form with planets around them, then thereÂ's got to be life everywhere," he asserts.

DonÂ't be quick to dismiss Welch as some starry-eyed, mad scientist; heÂ's not alone in his beliefs. When he leaves his mountaintop, he flies south to Berkeley where heÂ's a professor.

But heÂ's not just any professor - heÂ's the first at the University of California, at any university, to hold an endowed chair for the search for extraterrestrial intelligence.

"In our galaxy there are over 100 billion starsÂ…and when you look out there, we see over 100 billion galaxies. ThatÂ's a lot of stars," says Welch.

Welch does subscribe to the view of Star Wars that a long time ago, in a galaxy far, far away, intelligent beings lived and perhaps sent a beacon our way.

"What weÂ're looking for is really another civilization thatÂ's technically capable as we are, so that they could broadcast something in our direction and we could detect it," Welch says. "So what we are listening for is a signal that sounds like itÂ's man-made."

It may surprise you to know what Welch and many other sober scientists have contemplated: What if we make contact with aliens and they arenÂ't peaceful and loveable as in ET but vicious and villainous like the invaders of Independence Day?

Just in case, astronomers around the globe have argued that earthlings shouldnÂ't transmit any beacons alerting neighbors we are here.

"Probably itÂ's better to keep our heads down and just listen," Welch explains. "ThereÂ's a certain view that there might be some danger in being discovered - that if we are discovered by some advance civlizations, that they might come over and take us over."

"I donÂ't share that view myself, but a lot of people are worried about that," Welch adds.

Several times a year researchers are granted access to the giant dish at Arecibo, Puerto Rico, as featured in the film Contact. Together with others in Europe, Australia and around the world, they tune into space.

This is a passion Welch shares with his wife, Jill Tarter. She runs a Search for Extraterrestrial Intelligence, or SETI, project that was formerly with NASA and now a private institute.

"We have a target list that is a thousand stars. TheyÂ're nearby stars. ThatÂ's not very many," says Tarter.

"We live in a galaxy that has 400 billion stars, a half a trillion stars, so a thousand is just our cosmic back doorstep. But itÂ's where weÂ're starting," she says.

But after listening to so many stars for so many years, neither Welch nor Tarter nor any of their colleagues have ever heard anything, with the exception of galactic noise. Yet theyÂ're not discouraged.

TheyÂ're ready for the day they do detect that signal from space - a signal, Tarter says, that will result in ringing bells and dialing cellular phones and pagers, as in Contact.

In fact, Jody FosterÂ's character in Contact was based on Jill Tarter.

"This is a really special time in human history," says Tarter. "Before this epoch effort when we wanted to know whether we were alone in the universe all we could do was ask the priests and the philosophers."

"And theyÂ'd respond in terms of a belief system," she says. "But right now, for the first time, scientists and engineers can try and do an experiment that just might answer that question."

As impressive and successful as this Hat Creek facility is, it pales in comparison to what Welch and his star-searching colleagues are planning next. Imagine almost 1,000 dishes similar to the ones in Arecibo, covering one square mile. But first they must raise $25 million. Then the skyÂ's the limit.

"In the same time itÂ's taken us to do a thousand stars, we can certainly do 100,000 stars and then we can look at how we expand that to do a million," Tarter explains.

Welch and Tarter both know that some scientists think that what theyÂ're doing is not science, but science fiction.

"ItÂ's fun to read science fiction, but I donÂ't persuade myself that itÂ's real," says Welch. "And what weÂ're doing is to approach the thing from the scientific view as well as we can."

So Welch braves the skeptic wisecracks, convinced itÂ's more foolish not to look for life out there. HeÂ's convinced weÂ'll find it if we just listen hard enough. But does he believe it will happen in his lifetime?

"Probably not, but maybe," he says. "ThatÂ's what keeps me going."