The Search for Extraterrestrial Intelligence, a brief history

Is there anybody out there? If we don't listen for the answer, we certainly won't hear it. Over at the Planetary Society, Jason Davis posted an excellent survey of the past, present, and future of the search for extraterrestrial intelligence. It begins in 1959 with Giuseppe Cocconi and Philip Morrison's historic paper "Searching for Interstellar Communications" and Frank Drake's Project Ozma, the first scientific SETI search:

One year later, the National Academy of Sciences hosted an invitation-only meeting at Green Bank to discuss how to go about conducting further SETI research. The eclectic, interdisciplinary group included Drake, Cocconi, Morrison, the biochemist Melvin Calvin (who won the Nobel Prize in Chemistry during the meeting), Bernard Oliver, who was the vice president of research and development at Hewlett-Packard, the young Carl Sagan, and the scientist John Lilly, who had recently published a controversial book arguing dolphins were an intelligent species.

With a nod to Lilly's book, the participants dubbed themselves "The Order of the Dolphin." One product of the meeting was the Drake equation, which attempts to predict the number of advanced civilizations in the Milky Way able to contact Earth. The equation includes variables such as average star formation rate, the number of habitable planets per star, and the number of planets where intelligent life could evolve.

For the rest of the 1960s, SETI research remained mostly dormant, aside from a few searches in the Soviet Union. Starting in 1971, two Project Ozma follow-ups named Ozpa and Ozma II used bigger dishes and listened to more stars.

In 1973, another SETI search began, using a radio telescope called Big Ear at Ohio State University. Big Ear was a flat, aluminum dish three football fields wide, with reflectors at both ends.

On the night of August 15, 1977, Big Ear picked up a signal from the constellation Sagittarius that was 30 times stronger than the cosmic background noise, right at the 1,420 megahertz hydrogen line frequency. No one noticed it for a few days, until a volunteer sifting through the previous week's data circled the signal and wrote "Wow!" in the margin.

Jill Tarter is a legendary SETI scientist. She's the Bernard Oliver Chair for SETI at the SETI Institute in Mountain View, California, and is the inspiration for protagonist Ellie Arroway in Contact, played by Jodie Foster in the film adaptation.

Tarter told me Big Ear's automated search program had no built-in logic to stop and focus on the Wow! signal. Furthermore, there was no confirmation system such as a second telescope located elsewhere, which could help determine whether the signal was local to Earth or truly from the stars.

Despite decades of follow-up searches, the Wow! signal was never heard again. To this day, Tarter favors SETI programs that can process data in real time, rapidly follow-up on detections, and rule out local interference.

I asked her if the Wow! signal still haunts the SETI field. "Well, it haunts me," she said.

Is there anybody out there? (Planetary Society)