Gravity Probe B confirms Einstein’s Theories
IT TOOK FIVE DECADES from conception to results, but finally NASA’s Gravity Probe B has confirmed two cherished predictions of Einstein’s General Theory of Relativity.
“It is wonderful to have completed this landmark experiment testing Einstein’s universe. Einstein survives!” said Professor Francis Everitt of Stanford University, principal investigator of Gravity Probe B.
Not that Einstein’s theory was in any real danger of being proven wrong in the local environment of the Earth, nonetheless this long-awaited confirmation is worth celebrating.
Gravity Probe B used impeccably-designed gyroscopes to put Einstein to the test. Newton’s theory of gravity predicts that the axis of a gyroscope spinning freely in space, without any other forces to disturb its motion, would continue pointing in the same direction forever. Einstein begged to differ. His theory predicts that the fabric of spacetime around Earth is being warped by Earth itself (the geodetic effect), plus the rotating Earth is also dragging along spactime (the frame dragging effect), both of which would perceptibly change the direction of a gyroscope.
Both effects have been tested and confirmed by Gravity Probe B. Now, those interested in testing Einstein’s General Relativity will likely set their sights on large-scale phenomena (which occur on cosmological scales) and begin testing them with increasing accuracy.
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