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264 Detecting another civilization may destroy the chauvinism of specialness; learning about the history of intelligence over billions of years may destroy the chauvinism of time. The SETI 2020 report directly stated a major assumption of the radio search: “We expect communications, inadvertent or deliberate, to be com- monplace in an inhabited universe.”"’ De facto, human searchers define a technical civilization by its capacity to use powerful radio transmitters. And, we might add, by its interest in doing so. A society that does not emit strong electromagnetic signals may be invis- ible to us. If aliens used optical fibers for all of their communications, no radio waves would leak. Astronomer Jesse Greenstein speculated that all knowledge might be contained in a planetwide computer that radiates no energy into space and so communicates nothing."® Drake’s Warning Frank Drake’s own analyses showed that radio leakage from a planet is likely to get weaker as a civilization improves its communications tech- nology. He proposed in 1974 that when societies become more techno- logically sophisticated, they will reduce wastage of power and will become undetectable. Six years later, he wrote that mortal civilizations probably do not remain detectable forever, because their increasing technical sophistication enables them to cease the release of energy into space. Cell phone systems and satellite to home television require the sharing of frequency bands, driving us toward fainter, more targeted signals. To be realistic, we should assume that the same evolution of signal types will occur in other civilizations. The signals we have long assumed to be the right things to search for are fast disappearing, or fading, in our own civilization. If others follow a pattern of technological development similar to ours, we will be able to eavesdrop on their leakage only during the century after they develop radio. A similar evolution is under way in television signals. Engineering considerations would seem to ensure that we will eventually phase out TV broadcast services. “We're rapidly losing visibility—by a factor of 100,000,” said Drake. “Is that typical or quirky? We don’t know, but it’s a warning signal.” The implication is clear: We need to search for a much greater variety of electromagnetic emissions.” Before Contact They Will Be Detectable