spacetoday.net: Scientists measure speed of gravity

Posted: Sat, Jan 11, 2003, 11:15 AM ET (1615 GMT)
The first effort to measure the speed of gravity has led astronomers to conclude that gravity operates at the speed of light, as predicted by Einstein. Astronomers at the National Radio Astronomy Observatory and the University of Missouri measured the shift in the apparent location of a quasar as Jupiter passed close to it in the sky last September. A network of radio telescopes recorded the shift, caused by Jupiter's gravity bending the light; the precise amount of the bending depends on how quickly gravity propagates since Jupiter is moving around the Sun. The shift in the quasar's position as measured by astronomers is what would be expected if gravity propagates at the speed of light, astronomers found. That conclusion is in accordance with Einstein's general theory of relativity, but could put constraints on more exotic physics models, such as those that predict multiple dimensions, which require an infinite speed of gravity.