The Gravity Probe B gyroscopes are the most perfect spheres ever made by humans. If these ping pong-sized balls of fused quartz and silicon were the size of the Earth, the elevation of the entire surface would vary by no more than 12 feet.
Artist concept of Gravity Probe B spacecraft in orbit around the Earth. Image Credit: Stanford
Gravity Probe B is the relativity gyroscope experiment developed by NASA and Stanford University to test two unverified predictions of Albert Einstein's general theory of relativity. Launched on April 20, 2004, from Vandenberg Air Force Base, Calif., Gravity Probe B spent 17 months collecting data while in orbit around the Earth. Fifty weeks worth of data has been downloaded from the spacecraft and relayed to computers in the Mission Operations Center at Stanford University, Stanford, Calif. Since October 2005, scientists have conducted painstaking data analysis and validation.10.03.05 - After orbiting the Earth for more than 17 months, Gravity Probe B prepares to test Einstein's general theory of relativity.
05.03.05 - Is Einstein's general theory of relativity correct? Gravity Probe B tests two extraordinary predictions of that theory.
05.03.05 - Is Einstein's general theory of relativity correct? Gravity Probe B tests two extraordinary predictions of that theory.