NASA's Gravity Probe B spacecraft in orbit around Earth has allowed astronomers to confirm a prediction made by Einstein's theory of General Relativity. They were able to directly measure an effect known as "frame-dragging." According to Einstein's calculations, when a large, massive body such as the Earth rotates, it tends to pull the surrounding space around with it slightly, just as sticking a spoon in a jar of honey and twisting it will tend to drag around some of the honey.
The effect is extremely small -- amounting to about 6 feet (1.9 meters) in the distance that satellites, moving at about 18,000 miles per hour, cover in their orbits in a year -- but it is within the ability of NASA's tracking instruments to detect.
Read more at TechNewsWorld about the Einstein Gravity Effect Demonstrated by NASA.