Z
zavvy
Guest
<b>Spinning Earth Twists Space</b><br /><br />LINK<br /><br />One of the last untested predictions of general relativity has been confirmed by the first reasonably accurate measurement of how the rotating Earth warps the fabric of space.<br /><br />The experiment, carried out for virtually no cost with Earth-based laser range-finders, scoops Gravity Probe B, the US$700 million orbiting craft launched in April to test exactly the same effect. However, the Gravity Probe B team has questioned whether the result is really quite as accurate as it seems.<br /><br />The space warp is a consequence of Einstein's general theory of relativity, which describes gravity as a curvature in space produced by objects sitting in it. It also implies that a rotating mass will drag space around it like a spinning top placed in treacle - an effect known as the Lense-Thirring effect, or more commonly as 'frame-dragging'. The effect becomes important in understanding extreme situations like spinning quasars, and the rotation of jets of gas around black holes.<br /><br />The effect was first predicted by Austrian physicists Joseph Lense and Hans Thirring in 1918, but until now scientists haven't had sufficiently accurate instruments to measure its tiny perturbations in the fabric of our Universe. <br /><br />Ignazio Ciufolini at the University of Lecce, Italy and Erricos Pavlis at the University of Maryland in Baltimore charted the path of two NASA satellites, LAGEOS and LAGEOS 2, over 11 years with laser range-finders with the precision of a few millimetres. The effect dragged the satellite's orbits out of position by about 2 metres each year, the researchers report in this week's Nature1.<br /><br />The researchers say that their result is 99% of the value predicted by relativity, with an error of up to 10%. "Their result is the first reasonably accurate measurement of frame-dragging," comments Neil Ashby, a physicis