Dec 30 1975
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(New page: Pulsars had been discovered to be not only superdense but also superfluid, Columbia University physicists reported in Astrophysical Journal. Pulsars, collapsed remnants of exploded stars f...)
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Pulsars had been discovered to be not only superdense but also superfluid, Columbia University physicists reported in Astrophysical Journal. Pulsars, collapsed remnants of exploded stars formed almost entirely of neutrons, had been shown to be so dense that a spoonful would weigh millions of metric tons. Theorists had suspected that such objects, even with a thin rigid crust of iron, would be superfluid-a state produced experimentally on earth in small helium specimens cooled almost to absolute zero, where both friction and viscosity disappear. Material inside such an object, stirred into motion, would swirl indefinitely.
The Columbia Univ. experimenters had attempted to measure the surface temperature of a young pulsar, such as the one in the Crab Nebula. If the temperature were less than 8.8 million °C, the object would probably be superfluid; a fast-spinning neutron star would cool rapidly because of its reduced heat capacity. Temperatures of such objects could be detected by x-ray wavelengths, but the x-rays produced could not penetrate earth's atmosphere. Space observation was necessary, and rockets launched by NASA from Hawaii and N. Mex. tested the Crab nebula pulsar, using the moon as a curtain. As the moon passed across the whole nebula several times, cutting off its various x-ray emissions, the physicists had been able to identify the x-rays indicating temperature. Since the Crab nebula pulsar's temperature was shown to be less than 5 million °C, the physicists concluded that the pulsar must be superfluid. (NYT, 30 Dec 75, 40)
Predictions of a trend toward harsher winters for North America had been put in question by satellite monitoring of snowcover over the northern hemisphere during the past 9 yr, according to the National Oceanic and Atmospheric Administration. NOAA's National Environmental Satellite Service had published a document, "Monthly Winter Snowline Variation in the Northern Hemisphere from Satellite Records, 1966-1975," containing the most complete record available of hemisphere snowcover. Analysis of the charts had revealed no significant change in North American snowcover during the entire period. Predictions of harsher weather had raised the possibility of southward movement of the polar ice cap, which could be caused by a drop of only a few degrees in average winter temperature. The document concluded that "Lack of systematic increase in ... snow cover tends to contradict the evidence ... that the current climate is changing adversely." (NOAA Release 75-217)
President Ford had signed legislation establishing a 17-member U.S. Metric Board to plan for voluntary conversion of the nation to the metric system. Dr. Ernest Ambler, acting head of the National Bureau of Standards, said the signing of the bill would encourage U.S. industry and commerce to export products made to metric dimensions, which "should stimulate additional international trade." (SBD, 30 Dec 75,299)
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