Einstein was right! NASA probe confirms relativity

David Heath
Thursday, 05 May 2011 23:33

Science - Space

In planning since 1959, NASA's Gravity Probe B was launched in 2004 to test two key predictions of Einstein's Theory of Relativity.  With great success.

Einstein's General Theory of Relativity made two significant predictions which could be tested by the Gravity Probe B (GP-B) spacecraft:

The geodetic effect: the amount by which the Earth warps the local space-time in which it resides (also known as de Sitter precession);

The frame-dragging effect: the amount by which the rotating Earth drags its local space-time around with it (known as Lense-Thirring precession).

In other words, de Sitter is simply the warping effect on space-time of a large near-by mass (The Earth) while Lense-Thirring is an additional warping effect of that mass moving through space.

These two effects could be measured by the amount in which a carefully aligned and highly accurate gyroscope deviated over time.  A deviation of the rotating spin axis in the plane of the satellite's polar orbit would reveal the geodetic effect, while a change with reference to the plane of the earth's rotation would reveal the frame-dragging effect.

Project-member and low-temperature physicist William Fairbank observed:  "No mission could be simpler than Gravity Probe B.  It's just a star, a telescope, and a spinning sphere." 

Perhaps a little more than that - the spinning sphere was the most highly accurate sphere every constructed by man (in fact while only one was required for the experiments, 4 were included in the mission for redundancy); and the whole thing was surrounded by 2,440 litres of liquid Helium to maintain a sufficiently low temperature for the year-long experiment.

When considering the accuracy of the gyroscope spheres, NASA notes that if they were the same diameter as the Earth, the difference between the deepest ravine and the tallest mountain would be just 3.6 metres.