Word: pulsars
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Dates: during 1960-1969
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...months since British astronomers announced the discovery of pulsars, scientists have done a brilliant detective job of piecing together the nature of the strange, regularly beeping radio sources. Their effort has been all the more remarkable because they have never actually seen a pulsar; all of their clues come from radio signals picked up by giant radio telescopes...
...avenue of investigation has opened in the skies. Three University of Arizona astronomers have spotted a visible star that is located precisely where radio telescopes had detected a pulsar and is flashing at a rate identical to the pulsar's beeps. In all likelihood, they say, the flashing star is actually a pulsar...
...first inkling that pulsars might not be reliable timepieces came after Cornell University astronomers at Arecibo, Puerto Rico, trained their 1,000-ft. radio telescope on a newly discovered pulsar in the Crab Nebula, the glowing remnant of a supernova-or stellar explosion-that was seen from earth in A.D. 1054. Unlike most other pulsars, which have relatively low repetition rates (between one and four per second), the new find was ticking about 30 times per second. Carefully measuring the pulse rate in October and then again in November, the astronomers found that it was slowing down by about...
Match with Cesium. If earth time does indeed slow down relative to the pulsar clock in January, and speed up correspondingly in June, the pulsar signals (which have blipped at a constant frequency since they were discovered) would appear to increase their repetition rates as earth clocks slowed down and decrease them as earth time speeded up. Hoffmann's plan was immediately snapped up by Dror Sadeh, a Tel Aviv University physicist currently attached to the U.S. Naval Research Laboratory at Washington...
Sadeh feels sure that by January he should be able to detect an apparent speedup in the pulsar clock when compared with its rate this month-a clear indication that earth time has slowed by the same amount. If Einstein was right, that observed slowdown will total about 1/ 100th of a second per year. "If our measurements are accurate and we don't get this result," says Hoffmann, "then we scientists-and the Einstein theory-are in trouble...