![Artwork by Barron Storey of Gravity Probe B: What is Gravity Probe B?](https://www.nasa.gov/wp-content/uploads/2023/03/1_big_sat.jpg?w=1041)
Launched on April 20, 2004, Gravity Probe B (GP-B) was a collaboration between Stanford University and NASA designed to test two previously untested aspects of Albert Einstein’s general theory of relativity (geodetic and frame-dragging effects) by observing the precession of four near perfectly spherical gyroscopes.
Launched on April 20, 2004, Gravity Probe B (GP-B) was a collaboration between Stanford University and NASA designed to test two previously untested aspects of Albert Einstein’s general theory of relativity (geodetic and frame-dragging effects) by observing the precession of four near perfectly spherical gyroscopes in reference to a distant star as the spacecraft travelled in a polar orbit 400 miles above the Earth. The story of GP-B spans almost five decades and includes both a wide body of technical and scientific innovation and a remarkable collaboration between physics and engineering.
Image credit: Stanford University/Barron Storey