Gravity Probe B tested two predictions of Einstein's general theory of relativity by placing gyroscopes in a polar-orbiting satellite to measure how the Earth warps space and time. It measured the geodetic effect of how the Earth warps local space-time and the frame-dragging effect of how the rotating Earth drags space-time around with it. The experiment required extremely precise gyroscopes that could maintain accuracy of less than 0.5 milliarcseconds per year to verify Einstein's predictions.

1. By Jennifer Nalley Gravity Probe B

2. Gravity Probe B tested Einstein's ideas about space and time and how the Earth distorts them.

3. The Geodetic Effect: The amount by which the Earth warps the local space time in which it resides. The Frame Dragging Effect: The amount by which the rotating Earth drags local space time around with it. Although it had been dreamed of since 1959.... scientists lacked the technology that would allow them to verify two specific theoretical consequences of Einsteins General Theory of Relativity. A perfect plan.... that had to wait for technology to catch up.... And finally it did!!! Two Effects General Relativity Predicted The Frame Dragging Effect: The amount by which the rotating Earth drags local space time around with it.

4. Einstein Right Again? Gravity Probe B is the relativity gyroscope experiment developed by NASA and Stanford University to test two unverified predictions of Albert Einstein's general theory of relativity.

8. FAST FACTS Gyro Size 1.5 inches of fused quartz Sphericity < 40 atomic layers from perfect Quartz Purity Within 2 parts per million Gyro Spin Rate ~10,000 rpm Gyro Drift Rate < 10 -12 degrees/hour The Gravity Probe B Gyroscope...... is a 1.5-inch sphere of fused quartz, polished and “ lapped” to within a few atomic layers of perfect sphericity. A scan of its surface shows that only . 01 microns separate the highest point from the lowest point.

11. Time-line