Gravity Probe B, a NASA spacecraft to test two predictions of Albert Einstein's general theory of relativity, achieved a major milestone last week with the completion of the first phase of its mission and the transition into the science phase. The GP-B mission is now one step closer to shedding new light on the fundamental properties of our universe.
The spacecraft uses four ultra-precise gyroscopes to test two extraordinary predictions of Einstein's 1916 theory that space and time are distorted by the presence of massive objects. Specifically, it is testing two effects: 1) the geodetic effect--the amount by which the Earth warps local spacetime in which it resides, and 2) the frame-dragging effect--the amount by which the rotating Earth drags local spacetime around with it.
http://science.nasa.gov/headlines/y2004/20aug_gpbupdate.htm
http://einstein.stanford.edu/ (Stanford University) the mission's home page