Word: moons
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Dates: during 1940-1949
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...Wiggle. Soon after V-J day, the Signal Corps put Lieut. Colonel John H. DeWitt, a former radio "ham," in charge of a project called "Diana" (goddess of the moon, the wood, childbirth). No radically new apparatus was used, only a modified version of the standard "SCR-271" radar set, operating on its regular, fairly high frequency of 112 megacycles. The key play was in not sending out thousands of "pulses" of radio energy per second, which would not have allowed enough time in between for the moon echo to return; instead, Belmar sent out only one half-second pulse...
...pick up the feeble echo, the receiving apparatus had to be extra sensitive. Although the transmitter shot out 4,000 watts of power, echoing back from the moon came only 9/10,000,000,000,000,000 of a watt-that was strong enough to be received clearly. On the visual "scope" the echo showed as a wiggle in a luminous blue line, and could be heard as a brief hum. It came at the right time for a 450,000-mile round trip-about 2.4 seconds after the outgoing pulse...
...results. Sample check: the echo wave at moonrise-when the first contact was made-was slightly higher in frequency than the outgoing pulse. In accordance with the Doppler Effect, a wave reflected from an approaching body must increase its frequency. Chiefly because of the earth's revolution, the moon at that hour was moving toward the sending station at about 750 miles an hour...
...measuring stick in the universe. If light's velocity were proved to be variable, as some suspect, science's present conceptions of the universe would have to be scrapped. Since radio waves travel at the same speed as light, and the distance from the earth to the moon can be figured closely by triangulation, measuring the time it takes for a radar echo to come back from the moon should provide astronomers with a continuous check on the speed of light-and a double check on Dr. Einstein...
...Burton of the U.S. Naval Observatory (who should have known better) seemed to hope that Diana could be used to map the moon. But Diana's 12° radio beam is 24 times wider than the moon by the time it gets there. Even an enormously narrowed beam would not give more detail than a first-rate telescope. Other astronomers were inclined to sniff at the moon as finished astronomical business...