World's Most Precise Gyroscopes Ready To Test Einstein Theory: "A NASA spacecraft designed to test two important predictions of Albert Einstein's general theory of relativity is set to launch from Vandenberg Air Force Base, Calif., at 1 p.m. EDT, April 17.

"NASA's Gravity Probe B mission, also known as GP-B, will use four ultra-precise gyroscopes, orbiting the Earth in a unique satellite, to experimentally test two extraordinary predictions of Einstein's 1916 theory that space and time are distorted by the presence of massive objects."