If there are many billions of stars in every galaxy and billions and billions of galaxies, there must be at least billions of earth-like planets like ours and therefore plenty of opportunities for life to form and evolve. So, where is it?That was what Enrico Fermi wanted to know. The Hungarian nuclear physicist, who was closely associated with the formative years of Los Alamos, asked why, with all that potential, we still had no indisputable evidence for one living cell of life outside of earth, much less the obvious signs of intelligent life, like alien space probes or radio chatter. Those who subscribe to the Fermi Paradox, as it is known, say that the simplest explanation is that we are alone.But many others, including Jill Tarter, beg to differ. Tarter is the director of the Search for Extraterrestrial Intelligence (SETI) Institute in Mountain View, Calif. In a presentation at the Expanding Your Horizons workshop here Thursday, and an expanded presentation later that evening at the Bradbury Science Museum, she made a case for the importance of the search itself."My bottom line is - the search I helped to start may take a very long time, and may take some one like you to finish it.," she told the audience of 150 eighth through tenth graders, attending a career conference in Los Alamos. Tarter quoted from one of the pioneers of SETI research and another prominent figure from the Manhattan Project. Philip Morrison concluded a 1959 paper in Nature magazine with the line, "The probability of success is difficult to estimate; but if we never search, the probability of success is zero,"Life is a planetary phenomenon. The only life we know so far lives on a watery planet, not too close and not too far from a star with a long period of stable energy production, explained Tarter, a set of parameters that has focused astronomers to search for similar conditions in our galactic neighborhood.One result has been the discovery, so far, of 120 planets orbiting 105 other stars. "But good planets are hard to find," Tarter said. The planets that have been identified appear to be heavy gas giants, like the planets Jupiter and Saturn in our system, and closer to their star.A NASA spacecraft called Kepler, scheduled to launch in 2007, will specifically search for earth-like planets in a patch of sky containing 100,000 stars.Other SETI projects have used radio and optical telescopes to listen and watch for interstellar signs of life, radio frequencies and optical wavelengths that might indicate an intelligent source.
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