:: we have just folded space from Ix ::

Gravity Probe B sports the world's most spherical gyroscopes. (...) They are the most spherical objects in the universe, aside from neutron stars.
GP-B is among the most thoroughly researched programs ever undertaken by NASA. GP-B will measure two parts of Einstein's general theory of relativity by assessing how the presence of Earth warps space and time, and how Earth's rotation drags space and time.



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Gravity Probe B is the relativity gyroscope experiment being developed by NASA and Stanford University to test two extraordinary, unverified predictions of Albert Einstein's general theory of relativity.
The experiment will check, very precisely, tiny changes in the direction of spin of four gyroscopes contained in an Earth satellite orbiting at 400-mile altitude directly over the poles. So free are the gyroscopes from disturbance that they will provide an almost perfect space-time reference system*. They will measure how space and time are warped by the presence of the Earth, and, more profoundly, how the Earth's rotation drags space-time around with it. These effects, though small for the Earth, have far-reaching implications for the nature of matter and the structure of the Universe.


* Space-time is a four dimensional description of the universe that includes the usual three dimensions of height, width and length and a fourth dimension of time.