May 5, 2011 –Einstein was right again. There is a space-time vortex around Earth, and its shape precisely matches the predictions of Einstein’s theory of gravity. Researchers confirmed these points at a press conference today at NASA headquarters where they announced the long-awaited results of Gravity Probe B (GP-B). “The space-time around Earth appears to be distorted just as general relativity predicts,” says Stanford University physicist Francis Everitt, principal investigator of the Gravity Probe B mission. “This is an epic result,” adds Clifford Will of Washington University in St. Louis. An expert in Einstein’s theories, Will chairs an independent panel of the National Research Council set up by NASA in 1998 to monitor and review the results of Gravity Probe B. “One day,” he predicts, “this will be written up in textbooks as one of the classic experiments in the history of physics.” Time and space, according to Einstein’s theories of relativity, are woven together, forming a four-dimensional fabric called “space-time.” The mass of Earth dimples this fabric, much like a heavy person sitting in the middle of a trampoline. Gravity, says Einstein, is simply the motion of objects following the curvaceous lines of the dimple. If Earth were stationary, that would be the end of the story. But Earth is not stationary.
Our planet spins, and the spin should twist the dimple, slightly, pulling it around into a 4-dimensional swirl. This is what GP-B went to space in 2004 to check. The idea behind the experiment is simple: Put a spinning gyroscope into orbit around the Earth, with the spin axis pointed toward some distant star as a fixed reference point. Free from external forces, the gyroscope’s axis should continue pointing at the star–forever. But if space is twisted, the direction of the gyroscope’s axis should drift over time. By noting this change in direction relative to the star, the twists of space-time could be measured. The results of Gravity Probe B give physicists renewed confidence that the strange predictions of Einstein’s theory are indeed correct, and that these predictions may be applied elsewhere. The type of space-time vortex that exists around Earth is duplicated and magnified elsewhere in the cosmos–around massive neutron stars, black holes, and active galactic nuclei. “If you tried to spin a gyroscope in the severely twisted space-time around a black hole,” says Will, “it wouldn’t just gently precess by a fraction of a degree. It would wobble crazily and possibly even flip over.” For readers who are not experts in relativity: Geodetic precession is the amount of wobble caused by the static mass of the Earth (the dimple in space-time) and the frame dragging effect is the amount of wobble caused by the spin of the Earth (the twist in space-time). Both values are in precise accord with Einstein’s predictions. –NASA