探索外太空的生命迹象

For the last 50 years, scientists and astronomers have been training their telescopes into space in the search for signs of intelligent life. Frank Drake is a trailblazer in that quest.

Spellbound

Orson Wells' famous War of the Worlds radio broadcast in 1938 scared millions of Americans into believing earth was being invaded by Martians. But not a young Frank Drake. Rather than being fearful at the thought of aliens, he was captivated.

"My father told me there were other planets in space like the earth and this excited me," he says. "I was eight years old and this meant that a planet like where I lived with people like me and houses like me and eating food like I ate. The idea of there being other creatures in space is fascinating."

That fascination triggered many questions.

"It's the basis of so much exciting science fiction and the most popular movies ever made. It's just a subject which excites our curiosity. What would those other creatures be like? What would their histories be? Do they have technologies we don't have which we could benefit from? All of those things were the reasons that interested me."

Following his fascination

Drake pursued his boyhood interest and studied radio astronomy at Cornell and Harvard.

In 1960, he conducted the first search for extraterrestrial intelligence, a project now known as SETI. He looked for signals from these alien civilizations by setting up a 25-meter radio telescope in Green Bank, West Virginia and aiming it at two nearby stars.

"Much like the telescope that we use to look at the sky - at the stars and the planets - except that it receives radio waves instead of light waves. And at that time, we were on earth transmitting radio signals that were sufficiently powerful that our best radio telescopes of that day could detect them, across the great distances that separated the stars," says Drake. "And so it made sense to search for radio signals. We wouldn't be speculating or assuming super-civilizations or super technologies. All they had to have was technology like our own and we could find them."

SETI

At that time, Drake was a junior staff member at the National Radio Astronomy Observatory and kept quiet about his new project. It was so novel that he was concerned it might raise skepticism among colleagues and academics. But word of SETI got out and the public responded with support and donations.

Since 1960, there have been over one hundred SETI projects, with radio telescopes stationed around the world, including Puerto Rico, Argentina, Australia, South Korea and Italy. The equipment has become larger and more sophisticated over time. But so far, nothing has turned up. According to Drake, the universe is so big that it's hard to know where to look.

"We now listen not to one channel as I listened to back in 1960 in the first search, but tens of millions or even hundreds of millions of channels at once," he says. "So the search for the signals is actually carried out by computers looking at the deluge of information that is coming from the radio telescopes."

Continuing search

Although he is now retired from full-time teaching, Drake continues to provide guidance for the next generation of astronomers at the SETI Institute. He is renowned in the astronomy community and helps with much-needed fundraising to keep the work of SETI going.

"Frank Drake is a singular person. There's no other Frank Drake," says Seth Shostak, senior astronomer at the SETI Institute. "Frank being the first has led the way. I've been in places in rural Africa where Frank Drake is still a celebrity."

Now, the non-proft SETI Institute is spearheading efforts in the United States to build and set up larger and increasingly more sophisticated radio telescopes. Its latest project with the University of California, Berkeley, is the Allen Telescope Array, involving 42 radio antennas - the most advanced structure ever built to look for signs of extraterrestrial intelligence.

Although no signs of extraterrestrial intelligence have been detected, Drake remains optimistic.

"It's only a matter of time, and the amount of time is only a matter of money. We know how to make the search, we know how much searching is required, but it's very costly. And in time, as more funds are accumulated, we will carry out the search and eventually, we will succeed."

Does he think it will happen in his lifetime?

"Well, I'm 80 years old. And unfortunately, our best calculations tell us that even with our present very powerful equipment, the discovery is probably decades away. On the other hand, we could with very good luck chance upon a signal tomorrow."