Another exceptional human acheivement

[doodab]

What does it show that wasn't already shown by Eddington's 1919 eclipse observations?

Eddington measured gravitational lensing.

This measured the geodetic effect and frame dragging effect. It sounds like they failed somewhat, as the accuracy they achieved wasn't what they were shooting for.

The goal of the GP-B experiment is to measure the geodetic effect to an accuracy of ~0.01%, and to measure the frame-dragging effect, which has not previously been directly measured, to an accuracy ~1%.

And as Timberwolf pointed out they were beaten to the punch.

Even so, it's an impressively precisely made machine, as you can read here: Gravity Probe B — Extraordinayr Technologies

[Ignis Fatuus]

BBC News - Probe confirms Einstein effects

Bravo for clever people. Those are some very round balls.

What does it show that wasn't already shown by Eddington's 1919 eclipse observations?

[TimberWolf]

"For the geodetic effect, the predicted relativity effect is 6,606.1 of these milliarcseconds, and the measured result is a little over a quarter of a percent of that The frame-dragging we've measured to a little better than 20%."

It's been done better:

This is the first time frame dragging has been measured in this way. But it was measured previously in 2004 to about 10 per cent precision by its effects on the orbits of the LAGEOS I and II satellites. Tracking the motion of the moon with lasers has also measured frame dragging to a precision of 0.1 per cent.

Given these earlier results, questions are likely to remain about the value of Gravity Probe B's contribution, but Everitt defended the mission's value. "The great beauty of it is that we have complementary tests of general relativity," he said."We completed this landmark experiment testing Einstein's universe ... and Einstein survives."
Beleaguered mission measures swirling space-time at last - space - 04 May 2011 - New Scientist

[AtW]

I wonder what sasguru makes of it?

[doodab]

BBC News - Probe confirms Einstein effects

Bravo for clever people. Those are some very round balls.