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242 Dangers Astronomer Edward Purcell, who ridiculed the idea of interstellar travel, saw a conversation with a remote alien civilization as the ultimate in philo- sophical discourse; all you can do is exchange ideas. Morrison, too, dis- missed the risk of direct contact: “There will be absent across space, of course, any military dominance.” Sagan assured us that we will not at any time in the foreseeable future be in the position of the American Indians or the Vietnamese; we will not face “colonial barbarity” practiced on us by a technologically more advanced civilization. As he believed interstellar flight was possible, Sagan was forced to add a justification. We would be safe not only because of the great spaces between the stars, but also because Sagan believed that any civilization that has survived long enough for us to make contact with it would be benign or at least neutral.° Sagan’s Dilemma Sagan considered the vast distances that separate the stars to be provi- dential; beings and worlds are quarantined from each other. Yet, as early as 1962, he foresaw that starflight would be possible for civilizations more technologically advanced than our own, including future humans. Sagan fell back on the argument that there would be no danger because more advanced beings would be peaceful and benign. He also offered the peculiar thesis that the interstellar quarantine is lifted only for those with “sufficient self-knowledge and judgment” to have safely traveled from star to star. Sagan predicted that our descendants will interact harmoniously with more advanced species; quarrelsome humans in interstellar space are unlikely to last long. This would seem to imply that more powerful species would eliminate the quarrelsome ones. Sagan’s dilemma becomes more obvious when we consider his next argument: Alien science and technology will be so far beyond ours that “it is pointless to worry about the possible intentions of an advanced civilization.” Superior aliens could not possibly fear us—and we’re not likely to have anything they need. Then comes Sagan’s ultimate fallback position. If there are negative consequences, there will be nothing we can do about them.’ This strikes some as preemptive capitulation. Sagan’s dilemma illustrates a problem that runs through this debate. If you admit that interstellar flight is possible, you call into question the optimistic predictions made in the conventional SETI scenario. There Are No Dangers