Pale Blue Dot - Carl Sagan [127]
Weeks later, the signal was detected again. It turned out to be a military aircraft broadcasting on an unauthorized frequency. Drake reported negative results. But in science a negative result is not at all the same thing as a failure. His great achievement was to show that modern technology is fully able to listen for signals from hypothetical civilizations on the planets of other stars.
Since then there’ve been a number of attempts, often on time borrowed from other radio telescope observing programs, and almost never for longer than a few months. There’ve been some more false alarms, at Ohio State, in Arecibo, Puerto Rico, in France, Russia, and elsewhere, but nothing that could pass muster with the world scientific community.
Meanwhile, the technology for detection has been getting cheaper; the sensitivity keeps improving; the scientific respectability of SETI has continued to grow; and even NASA and Congress have become a little less afraid to support it. Diverse, complementary search strategies are possible and necessary. It was clear years ago that if the trend continued, the technology for a comprehensive SETI effort would eventually fall within the reach even of private organizations (or wealthy individuals); and sooner or later, the government would be willing to support a major program. After 30 years of work, for some of us it’s been later rather than sooner. But at last the time has come.
THE PLANETARY SOCIETY—a nonprofit membership organization that Bruce Murray, then the Director of JPL, and I founded in 1980—is devoted to planetary exploration and the search for extraterrestrial life. Paul Horowitz, a physicist at Harvard University, had made a number of important innovations for SETI and was eager to try them out. If we could find the money to get him started, we thought we could continue to support the program by donations from our members.
In 1983 Ann Druyan and I suggested to the filmmaker Steven Spielberg that this was an ideal project for him to support. Breaking with Hollywood tradition, he had in two wildly successful movies conveyed the idea that extraterrestrial beings might not be hostile and dangerous. Spielberg agreed. With his initial support through The Planetary Society, Project META began.
META is an acronym for “Megachannel ExtraTerrestrial Assay.” The single frequency of Drake’s first system grew to 8.4 million. But each channel, each “station,” we tune to has an exceptionally narrow frequency range. There are no known processes out among the stars and galaxies that can generate such sharp radio “lines.” If we pick up anything falling into so narrow a channel, it must, we think, be a token of intelligence and technology.
What’s more, the Earth turns—which means that any distant radio source will have a sizable apparent motion, like the rising and setting of the stars. Just as the steady tone of a car’s horn dips as it drives by, so any authentic extraterrestrial radio source will exhibit a steady drift in frequency due to the Earth’s rotation. In contrast, any source of radio interference at the Earth’s surface will be rotating at the same speed as the META receiver. META’s listening frequencies are continuously changed to compensate for the Earth’s rotation, so that any narrow-band signals from the sky will always appear in a single channel. But any radio interference down here on Earth will give itself away by racing through adjacent channels.
The META radio telescope at Harvard, Massachusetts, is 26 meters (84 feet) in diameter. Each day, as the Earth rotates the telescope beneath the sky, a swath of stars narrower than the full moon is swept out and examined. Next day, it’s an adjacent swath. Over a year, all of the northern sky and part of the southern is observed. An identical system, also sponsored by The