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Reflections on Forty Years of Optical SETI --
 Looking Forward and Looking Backward


Charles H. Townes


Picture by Tom McDonough, The Planetary Society, 1993






When, in early 1961, interstellar communication with lasers was first discussed, it was met with interest but not enthusiasm.  The scientific community was thinking of laser powers in the kilowatt range (which had not yet been actually achieved) and telescopes of maximum diameter 200 inches.  Now there are lasers of average power 106 watts, pulsed power 1015 watts, and telescopes of diameter 10 meters.  Just what technology an advanced extrasolar civilization would have is still debatable, but on earth communication with lasers is growing rapidly and now "Optical SETI" seems to many a likely  prospect.  In addition to increased power and variety of lasers, with expectation of further growth, the easy use of short pulses alleviates the need for high spectral resolution required by CW laser communication, and gives high signal to noise  ratios.  Such changes in our own technology and views over only a few decades obviously stimulate open-mindedness about  the state of technical developments and communication in any external civilization.  And what are the resulting speculations?


Keywords: Optical SETI, 1961, lasers, communications, technology, history.
















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