NASA / SCIENCE PHOTO LIBRARY NASA / SCIENCE PHOTO LIBRARY
Gravity Probe B (GP-B) satellite, computer artwork. The Earth is shown warping a grid of space-time. The GP-B satellite (left) was used to investigate some predictions of Einstein's theory of General Relativity. This theory presents gravity as a warping of space and time. The GP-B used a telescope and four gyroscopes to try to detect both the Earth's warping of space-time, and also the predicted 'drag' on space-time caused by the rotation of the Earth. The satellite was launched in 2004, and the experiment finished in September 2005. The analysis of the results is ongoing, as of 2009, but has so far confirmed the Earth's warping of space-time to an uncertainty of less than 0.5 per cent.
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