Ref: http://www.sciencenews.org/20031101/bob9.asp

A satellite designed to test one of the more twisted predictions of
Albert Einstein's general theory of relativity is finally at its
launch site after 40 years of preparation. The probe will look for
evidence of a gravitational effect known as frame dragging. Just as a
dipper drags honey along as it twirls in a honey jar, any spinning
body in space, including Earth, ought to drag some space-time along
with it. That was Einstein's prediction, anyway. The effect has never
been convincingly observed.

That's partly because Earth's tweaking of space should barely
register on even the most sensitive instruments. Yet the effects of
frame dragging may prove enormous in deep space where spinning,
ultradense concentrations of mass known as supermassive black holes
may torque space-time vigorously enough to create the enormously
powerful jets of matter and energy known as quasars (SN: 4/5/03, p.
214: http://www.sciencenews.org/20030405/fob7.asp).

Many relativity experts are enthusiastic about the prospects for
Gravity Probe B (GP-B), as the spacecraft is known. Gathering hard
evidence that "space is not the fixed fabric we think of" would be a
"stunning achievement," says Clifford M. Will of Washington
University in St. Louis, a gravitational physicist who served on a
NASA-convened review panel that endorsed the mission's science goals
last spring. He adds, "It's the kind of result that will be written
in physics textbooks for years to come."

See: http://www.sciencenews.org/20031101/bob9.asp