A young Frank Drake. Photo: NRAO/AUI

A year before Yuri Gagarin orbited the Earth and nine years before Neil Armstrong set foot on the moon, astronomer Frank Drake launched one of the most intriguing space explorations of the millennium.

On April 8, 1960, in a wind-swept valley near Green Bank, West Virginia, Drake flipped switches, twisted knobs, and then pointed an 85-foot radio telescope at two nearby stars - Epsilon Eridani and Tau Ceti. His aim: to 'listen' for signs of communication technology emanating from a civilization beyond Earth.

Drake's experiment, named Project Ozma for the mythical princess of Frank L. Baum's "Wizard of Oz" books, initiated the modern scientific search for extra-terrestrial intelligence, commonly known by its acronym, SETI. April 8, 2000, marks the 40th anniversary of this experiment, which spawned a field of scientific inquiry and experimentation that continues to capture the imagination of the world. This year, April 8 is also International Astronomy Day.

The first search
Project Ozma followed on the heels of a ground-breaking paper published the year before by Cornell University physicists Giuseppe Cocconi and Philip Morrison. That paper suggested that radio waves might be the most effective means of communication across galactic distances, and therefore could be the best way to detect the existence of an extra-terrestrial civilization.

Drake, then an astronomer at the National Radio Astronomy Observatory in Green Bank, had independently come to the same conclusion. He also felt he had the means to test the theory.

"At that time we were building new, large telescopes, and more importantly, several new forms of radio receivers had been invented which gave sensitivities about 10 times better than the vacuum-tube based receivers then in common use," Drake said. "The combination of the bigger telescopes and the more sensitive receivers allowed us, for the first time, to detect radio signals from the distances of the nearest Sun-like stars of the same strength we were then sending into space.

"To put it another way, we had crossed a threshold where we could detect civilizations like our own across the distances which separate the stars."

Drake remembers that it was cold in the early morning of April 8.

"We started tuning these fancy receivers at about 4 a.m.," recalled Drake, who at the time was about a month shy of his 30th birthday. "It was nearly freezing. The tuning had to be done in the feed enclosure, a little larger than a garbage can, at the focus of the 85-foot antenna. These receivers were new and very tempermental, and they took about an hour of complicated tuning to make them work the way we needed them to. Only two people in the world knew how to do it, the engineer who built them, and myself."

False alarm
Project Ozma finally commenced observations at about 6 a.m. - and almost immediately picked up a signal.

"We had a big, loud, false alarm the first day," Drake said. "Of course, we didn't identify it as such until weeks later, and at the time we were very excited. We couldn't believe our luck."

The false alarm turned out to be a secret military project.

Project Ozma observed for a total of about 200 hours over a period of two months. Even though it didn't detect signals from civilizations beyond Earth, it did prompt the Space Sciences Board of the National Academy of Sciences to tap Drake to organize the first major meeting about the search for extra-terrestrial intelligence.

As an agenda for that meeting (whose participants included, among others, a young Carl Sagan), Drake formulated what later became commonly known as the Drake Equation. The equation, still widely used, is a formula that estimates the number of civilizations in the galaxy which might be capable of developing detectable communication technology.

The first of many SETI projects
Drake's pioneering experiment ultimately led to more than 60 SETI projects, including a major NASA effort in the 1980s and early 1990s and several experiments in the former Soviet Union.

Several current SETI efforts use the giant radio telescope at Arecibo in Puerto Rico. Photo: Seth Shostak/SETI Institute

Several large SETI projects continue today. The largest of these, Project Phoenix, is privately supported and conducted by the California-based SETI Institute, of which Drake is President of the Board of Directors. Project Phoenix and its scientists are widely held to be the inspiration for much of the 1997 Jodie Foster film, Contact. Drake also serves as Research Professor of Astronomy at the University of California-Santa Cruz and, among his many honors, is a member of the National Academy of Sciences.

Today, Drake is as active in planning the future of SETI as he was in launching it 40 years ago. Drake is on the steering committee for a new SETI telescope project. Planned as an array of small, 'off-the-shelf' satellite-style dishes linked together by sophisticated electronics, the new telescope will advance SETI by providing more observing time and greater sensitivity to weak signals. The new telescope will also have numerous applications for general radio astronomy.

An early prototype of the new SETI telescope will be launched in mid-April at a site near the University of California-Berkeley, which is partnering with the SETI Institute to build the instrument.

"Our equipment today is 100 trillion times more powerful than the Ozma equipment," marveled Drake. "Even so, Ozma wasn't a waste - it had a real chance to succeed, even with the technology of the time. And in science you have to advance by climbing the ladder one step at a time."