Gravity Probe B

Описание: The experiment planned to check, very precisely, tiny changes in the direction of spin of four gyroscopes contained in an Earth satellite orbiting at 650 km (400 mi) altitude, crossing directly over the poles. The gyroscopes were so free from disturbance that they provided a near-perfect space-time reference system. They were intended to measure how space and time are "warped" by the presence of the Earth, and by how much the Earth's rotation "drags" space-time around with it. This is the so-called frame-dragging effect, an example of gravitomagnetism. It is an analog of magnetism in classical electrodynamics, but caused by rotating masses rather than rotating electric charges.