Word: seismicity
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These sound waves, or seismic waves, cannot travel in space because there is no air or other medium to carry them. So when the waves reach the surface of the sun from below, they bounce back into the interior, where the greater heat bends them toward the surface again. The result, says astronomer Robert Noyes of the Harvard-Smithsonian Center for Astrophysics, is a "sun ringing like a bell, but not one that is being struck by a clapper. Rather, it is vibrating somewhat like a bell suspended in a sandstorm, continuously struck by tiny grains of sand...
...astrophysicist at the University of Colorado, "the waves cause the gases there to move up and down" -- oscillations that astronomers can measure. To date, they have discovered millions of different oscillations, up- and-down motions with cycles ranging from 2 1/2 to 13 minutes. Some are caused by seismic waves confined to a zigzag path near the surface, others by waves that plunge as far as four-fifths the distance to the solar center before being deflected back...
Just as seismologists describe the structure and nature of the earth's interior by studying seismic waves caused by earthquakes or explosions, astronomers are using helioseismology to learn more about the structure of the sun. Although still in its infancy, the new science has already led to several discoveries. Says NSO's Harvey: "It looks as if the frequencies of the oscillating waves vary with the solar cycle: they decreased a bit as the sun went toward solar minimum. Now we expect them to increase again...
Above all, abortion activists predict that the struggle could lead to a seismic shift in American politics, becoming a constant factor in nearly every election and threatening to fracture both parties. Like civil rights and the Viet Nam War in the 1960s, abortion could be the great preoccupation of the 1990s. "It will be a battle for years and years and years," says Samuel Lee, executive director of Missouri Citizens for Life, which helped write the law at issue in the Webster case. "I don't think it's ever going to go away...
...terms of the death toll, the temblor was among the century's worst. In terms of the magnitude of the shock, though, it was a good deal less severe: the quake that hit Mexico City in 1985, for example, was a considerably more destructive 8.1 seismic shock, yet fewer than 10,000 people died. Experts laid much of the blame for last week's shocking toll on the shoddy construction of the buildings in Armenia's cities and towns. According to Brian Tucker, acting state geologist of California who has visited Armenia, many buildings in the region are made...