Widgets Magazine

Gravity Probe B confirms two tenets of Einstein’s theory

A Stanford and NASA team led by physics professor Francis Everitt confirmed two tenets of Albert Einstein’s theory of general relativity, ending one of the space agency’s longest-running ventures.

The project, which was geared toward developing and using a satellite called Gravity Probe B (GP-B), spanned five decades and ultimately cost more than $750 million. It was designed to empirically study the geodetic effect, which is the warping of space and time around gravitational bodies, and frame-dragging, which is how much a spinning object carries time and space as it rotates.

“GP-B confirmed two of the most profound predictions of Einstein’s universe, having far-reaching implications across astrophysics research,” Everitt said in an interview with the Stanford Report. “Likewise, the decades of technological innovation behind the mission will have a lasting legacy on Earth and in space.”

The experiment was dreamed up in 1959, but at the time, the technology wasn’t available to create such a device. GP-B was to house a star tracker and four ultra-precise gyroscopes that would then orbit Earth at about 400 miles above the surface.

After more than four decades, the probe finally made it to orbit in 2004 and ran for 17 months. Unexpected electrical charge on the gyroscopes, which were niobium superconductors, caused them to inadvertently twist, throwing off the satellite’s readings. It took five years to obtain the data.

Technologies developed for GP-B have led to systems that can control aerodynamic drag, magnetic field and thermal variation. They have helped advance the Global Positioning System (GPS) and NASA’s Cosmic Background Explorer mission, which estimated the universe’s background radiation and lent empirical support to the “big bang” theory.

–Tyler Brown