Word: pulsars
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Dates: during 1968-1968
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...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...
...more that astronomers learn about pulsars, the still-to-be-identified bodies that are sending strange beeping signals from the Milky Way, the more difficult to identify the pulsars become. Last week, at a Manhattan gathering of the growing group of pulsar specialists, scientists from the Kitt Peak National Observatory in Arizona and the Lick Observatory in California disclosed that Pulsar I not only sends out high-frequency radio signals every 1.3 seconds, but also gives off light flashes just about half as often. The conferees were beginning to ponder this new information when a tardy University of California astronomer...
What does it all mean? The confusing combination of light and radio pulses has persuaded most astronomers that pulsars are not white dwarfs (small, dying stars). And although British pulsar discoverers initially nicknamed them LGM (little green men), most astronomers have now given up the idea that the four known pulsars might somehow be powerful electronic beacons from a super civilization in distant space. Still in the running is the notion that they may be neutron stars: tiny bodies of densely packed neutrons, which are atomic particles having no electrical charge. The only thing that seems reasonably certain is that...