http://www.bbc.co.uk/news/science-environment-13286241"Gravity Probe B was put in space to confirm two important consequences stemming from Einstein's Theory of General Relativity - his description of gravity. The predictions characterise the way space and time will be distorted by the presence of huge objects such as planets and stars.
One, known as the geodetic effect, is the amount by which the mass of the Earth will warp the local space-time in which it sits.
The other, which physicists refer to as frame-dragging, is the phenomenon that sees the Earth twist local space-time around with it as it rotates."
-Amazing!