Mar 26 1998
From The Space Library
An international team of researchers announced that observations of U.S. satellites orbiting Earth had proven one of physicist Albert Einstein's theories correct. In his general theory of relativity, Einstein had predicted that a spinning body could curve space, because the "spin of a body must change the geometry of the universe by generating space-time curvature." Einstein had called the phenomenon frame dragging, but scientists came to refer to it as the Lense-Thirring effect, naming it for two Austrian physicists who wrote that rotating celestial bodies, such as the Sun, "create a force that pulls space toward them." Ignazio Ciufolini, a physicist at Sapienza University of Rome, and his colleagues used lasers to measure changes in the orbits of the Laser Geodynamics Satellite I, or LAGEOS, a NASA spacecraft, and LAGEOS II, a satellite belonging to NASA and the Italian Space Agency. The research team observed changes that they could not account for by the laws of gravity or tidal forces, concluding that the Lense-Thirring effect exists. The satellites, launched in 1976 and 1992, were passive satellites dedicated exclusively to laser ranging. In this process, scientists had send laser pulses to the satellite from ranging stations on Earth, measuring the round-trip travel time of the pulses. The research team had analyzed data collected over a four-year period beginning in 1993.
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