The rotational speed of the Earth’s inner core is not constant and constantly rises and falls. About informs TASS, referring to the press service of the University of Southern California.
“Our measurements made it possible to be sure that the rotational rates of the earth’s crust and inner core, which theorists have argued for over two decades, are indeed different. At the same time, we learned that this ratio changes periodically – it fell in 1969-1971 and began to grow in 1971-1974. This , indicates periodic fluctuations in the rotational speed of the inner core,” said Professor John Vidal.
This was found thanks to nuclear tests in the USSR and the USA in 1969-1974. They took place at the underground training grounds on Novaya Zemlya and on the American island of Amchitka. Seismic waves from the explosion of Soviet and American test loads were continuously recorded by the American military seismograph LASA, based in Montana. Some of these fluctuations reached the Earth’s inner core and were reflected back; Scientists used it to predict the rotational speed of the planet’s central region. In particular, it was possible to find that in 1969-1971 the inner core rotates slower than the Earth’s surface, and in 1971-1974 – faster than the surface.
Scientists are still not clear on what causes such fluctuations, but they explain why the length of the day on Earth changes by plus or minus 0.2 seconds every six years. More seismic measurements are needed to determine the cause of the oscillations.
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