Credit: Bob Kahn/Gravity Probe B/Stanford University
Fifty years after it was conceived, a $760 million NASA spacecraft has confirmed Einstein's theory of gravity, or general relativity, physicists announced today. Gravity Probe B achieved measurements that agreed with theoretical predictions for two effects of general relativity, which states that gravity arises when mass bends space and time. "Einstein survives!" said Francis Everitt, a physicist at Stanford University in Palo Alto, California, who reported the results at a press conference at NASA headquarters in Washington, D.C.
Other researchers, however, greeted the results with what amounted to polite applause. Gravity Probe B fell well short of the precision developers had hoped to achieve in making the key measurement. Moreover, the project got scooped 6 years ago, when two physicists made a similar measurement using data from much cheaper satellites. "I have to compliment the Gravity Probe B team for their result, because Gravity Probe B is a very difficult and very beautiful experiment," says Ignazio Ciufolini, a physicist at the University of Salento in Lecce, Italy, who made the earlier measurement. See:At Long Last, Gravity Probe B Satellite Proves Einstein Right
See Also: Gravity Probe B final results: frame dragging within 20 percent
To test Einstein's theory of general relativity, Gravity Probe B must measure two minuscule angles with spinning gyroscopes, floating in space. While the concept of Gravity Probe B is relatively simple, carrying out the experiment required some of the most accurate and sophisticated technology ever developed. In fact, scientists and engineers from Stanford, Lockheed Martin, and NASA had to invent over a dozen totally new technologies in order to meet GP-B’s near-zero constraints, because much of the technology required simply did not exist when the experiment was first suggested in late 1959 - early 1960. Einstein, himself once a patent clerk, would have enjoyed reviewing these extraordinary technologies. This section describes the technologies of the four systems that comprise the heart of the GP-B experiment. See: The Extraordinary Technologies of GP-B