Diana

Until Jan. 10, 1946, scientists had been experimentally limited to the earth and to a thin shell of air around it. Last week, the U.S. Army Signal Corps announced a scientific milestone: on Jan. 10 (and several times since), its radar at Belmar, N.J. had sent a message to the moon and got an answering echo. Man had finally reached beyond his own planet.

Hum & 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 every five seconds.

To 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.

The Signal Corps repeated the experiment many times, and disinterested scientists checked the 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.

Einstein & Venus. Although many scientists pointed out that the Belmar technique was too crude at present to drag much new information down from space, they speculated happily on what it might accomplish in the future.

Harvard's Astronomer Fred L. Whipple thought Diana might provide a test of Einstein's Theory of Relativity. According to Einstein, the velocity of light is constant, which makes it the basic 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.

H. E. 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 12DEG 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.*

Perhaps Diana could reach the planets? Not with present apparatus, said the Signal Corps. Far from being just a quarter of a million miles around the corner like the moon, Venus never comes nearer than 26,000,000 miles, Mars 35,000,000 miles. Still--no one was rash enough to say that it could never be done. (One technician put it in terms of rocket ships: 90 hours to the moon; to Mars and back, two and a half years.)

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First to pounce on the commercial possibilities was I.T. & T.'s Federal Laboratories, which announced plans for New York-Paris communication via the moon (visible from both cities almost twelve hours a day). Advantages: 1) high-frequency waves, which do not curve efficiently with the earth's surface, would bounce off the moon in straight lines; 2) earthy atmospheric troubles would be avoided.

*Generally accepted beliefs about the moon; it is 2,160 miles in diameter (earth: 7,920), and not exactly spherical (nor is the earth); it has no atmosphere, no moisture, no inhabitants; the "day" is 29 1/2 earth days long; at "noon" the temperature touches 261DEG Fahrenheit, and at night it falls to minus 243DEG; the mountains are straight, jagged, miles-high peaks into the emptiness; deep crevasses crack the flatlands, which are covered with fine meteoric dust. Biggest mystery: the "other side" of the moon. The moon revolves on its axis in exactly the time it takes for it to circle the earth, so it always presents the same face to an earthly observer.

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