“Almost 90 years after Einstein postulated his general theory of relativity — our current theory of gravity — scientists have finally finished collecting the data that will put this theory to an experimental test. For the past 17 months, NASA’s Gravity Probe-B (GP-B) satellite has been orbiting the Earth using four ultra-precise gyroscopes, about a million times better than the finest navigational gyroscopes, to generate the data required for this unprecedented test. As planned, the helium that cooled the experiment and powered its micro-thrusters has run out, ending the data-collection and final instrument calibration phase of the experiment. All the data—50 weeks’ worth—has been downloaded from the spacecraft and relayed to computers in the GP-B Mission Operations Center at Stanford University, where GP-B scientists have begun the final painstaking task of data analysis and validation. Was Einstein correct? They won’t know for another 15 months, when the analysis has been completed, but physicists around the world are eagerly awaiting the results.”