spacetoday.net: Satellite experiment supports general relativity

Posted: Sat, Oct 23, 2004, 4:49 PM ET (2049 GMT)
Physicists using a pair of existing spacecraft have provided experimental evidence supporting one of the central tenets of general relativity. In a paper published in the journal Nature on Thursday, scientists in Italy and the US reported that their measurements of the orbits of the satellites LAGEOS 1 and 2 proved the existence of "frame dragging", a phenomenon predicted by general relativity where a spinning body drags spacetime around it. The physicists found that, once correcting for the Earth's own gravitational perturbations, the orbits of the two satellites shifted by about two meters per year, 99 percent of the shift predicted by general relativity, although the measurements have a margin of error of about five percent. Earlier this year NASA launched Gravity Probe B, a mission dedicated to measuring the effects of general relativity, including frame dragging to within a margin of error of one percent.