1 The 85-foot diameter Howard Tatel Telescope at the National Radio Astronomy Observatory, Green Bank WV, used by Frank Drake for his Project Ozma observations in April and May of 1960. 

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... was an idea whose time had come, but nobody dared admit that out loud. Frank Drake, in particular, was keeping silent. Like many of his generation, he had long speculated about the existence of extraterrestrial life, and pondered how we humans might probe for direct evidence of our cosmic companions. Now, in 1959, the young astronomer was finally in a position to do more than ponder. At 29, he had just completed graduate school, the ink on his Harvard diploma as wet as he was behind the ears. As the new kid on the block at the National Radio Astronomy Observatory, he had access to the tools necessary to mount a credible search for radio evidence of distant technological civilizations. Drake knew enough to tread lightly; a publicly announced hunt for Little Green Men would be tantamount to professional suicide, so he approached his superior with understandable trepidation. Fortunately, NRAO director Otto Struve was sympathetic, even as he counseled caution. Having theorized that the slowed rotation rate of certain stars suggested that their angular momentum had been dissipated in the formation of planets, Struve himself speculated on the probable existence of extraterrestrial civilizations. So, he authorized Drake to use the 85 foot diameter Howard Tatel telescope ( Figure 2.1) in his off-duty time, to conduct what was to become the world’s first observational SETI experiment. Only, do so quietly, Struve warned; we don’t want the word getting out that we’re using a government facility to hunt for aliens. Drake had already run the numbers. He knew the most likely frequency on which to search, and the best receiver circuitry to employ. He had picked his candidate stars, two nearby sunlike ones which he reasoned were likely to harbor habitable planets. He had selected his research methodology, and proceeded (very quietly) to assemble his listening station. And then, the Nature article hit the newsstands. “Searching for Interstellar Communications” was written by two Cornell University professors, Giuseppe Cocconi and Philip Morrison, and it proposed, in brief but clear detail, the very experiment which Drake was preparing to conduct! This very first scientific article in the not-yet-named discipline of SETI was complete, down to the selection of frequencies and target stars – and it paralleled Drake’s work exactly. Neither the team of Morrison and Cocconi, nor that of Drake and Struve, knew anything about the others’ interest in this esoteric study. Both groups had arrived at the same crossroads in history, completely independently, in an elegant example of what I like to call the Parenthood Principle: when a great idea is ready to be born, it goes out in search of a parent. Sometimes, it finds more than one. Now Schrodinger’s Cat was out of the bag, and Drake had no choice but to go public. The publicity he received was widespread, and generally enthusiastic; the scientific community, it appeared, was ready to embrace the notion of SETI. Struve began writing about the possibility of extraterrestrial life: “An intrinsically improbable event may become highly probable if the number of events is very great... it is probable that a good many of the billions of planets in the Milky Way support intelligent forms of life. To me this conclusion is of great philosophical interest. I believe that science has reached the point where it is necessary to take into account the action of intelligent beings, in addition to the classical laws of physics.” His cover now blown, Drake soon found himself in the company of other open-minded scientists and technologists, who collectively found themselves unwitting parents to a newly-emerging scientific discipline. Among those contacting Drake after reading about his nascent experiment were: microwave communications expert Bernard M. Oliver, then vice- president of engineering at Hewlett-Packard (and, later, president of the Institute of Electrical and Electronic Engineering); Dana Atchley, president of Microwave Associates in Massachusetts; and a young planetary scientist, Berkeley post-doctoral researcher Carl Sagan. These individuals, as well as Struve, Morrison, and a handful of others, were ultimately to become SETI’s patriarchs. (Cocconi, though having co-authored the seminal SETI article with Morrison, went on to distinguish himself in particle physics research at CERN, never to return to the SETI fold.) Drake named his search Project Ozma, after the princess of Oz in the L. Frank Baum books, as he saw his efforts leading humans to a far-off and exotic land. Launched in April 1960, and running only through May of that year, Ozma searched only two stars, on a single frequency, for mere dozens of hours, but established the protocols and laid the groundwork for all subsequent SETI experiments. It was a paradigm-shifting endeavor, successful for its audacity, if not for its discoveries. And yet, for one brief moment early on, Frank Drake thought he had hit paydirt. As he slewed his antenna off Tau Ceti and onto Epsilon Eridani, he was greeted with a strong, periodic, pulsed signal on 1420 MHz, the hyperfine transition emission line of interstellar hydrogen atoms proposed by Cocconi and Morrison, and still favored as a promising hailing frequency for interstellar communications. “My god,” Frank mused, “can it really be this easy?” The next day, when the signal reappeared, Drake was ready with a second, low-gain antenna. The pulses were there as well, sadly disproving their extraterrestrial origin. But they were not exactly terrestrial interference, either. The rate at which the phantom signal traversed the sky suggested that it was emanating from an aircraft cruising at unprecedented altitude – perhaps 80,000 feet! Of course, in April 1960, no known aircraft could reach the stratosphere. Such an aircraft, as it happened, didn’t “come into existence” until the following month, when Francis Gary Powers was shot down over the Soviet Union. (Frank wisely decided to withhold publication of this positive result, so he never did receive proper credit for “discovering” the U-2.) A year after Project Ozma’s brief tenure, Drake convened at Green Bank the first scientific conference devoted to modern SETI. He gathered together 10 scientists from ...