A U.S. space probe carrying four gyroscopes has confirmed two key elements of Albert Einstein's theory of relativity, according to the journal Physical Review Letters.

Gravity Probe B, built by Lockheed Martin Corp. and designed by scientists from Stanford University near Palo Alto, California, was launched in 2004 to test how space and time are warped by gravitational bodies.

According to a statement posted in U.S. National Aeronautics and Space Administration's Web site, the Gravity Probe B (GP-B) mission used four ultra-precise gyroscopes to measure the hypothesized geodetic effect, the warping of space and time around a gravitational body, and frame-dragging, the amount a spinning object pulls space and time with it as it rotates.

GP-B was made to point at a single star, IM Pegasi, while in a polar orbit around Earth. If gravity did not affect space and time, GP-B's gyroscopes would point in the same direction forever while in orbit, as Isaac Newton had theorized. Instead, in confirmation of Einstein's theories, the gyroscopes experienced measurable, minute changes in the direction of their spin, while Earth's gravity pulled at them.

"Imagine the Earth as if it were immersed in honey. As the planet rotates, the honey around it would swirl, and it's the same with space and time," said Francis Everitt, GP-B principal investigator at Stanford University, in a statement. "GP-B confirmed two of the most profound predictions of Einstein's universe, having far-reaching implications across astrophysics research. Likewise, the decades of technological innovation behind the mission will have a lasting legacy on Earth and in space."

The project was one of the longest-running efforts in theU.S. space agency's history, beginning in 1963, and cost about US$750 million, NASA spokesman Trent Perrotto said today in atelephone interview with Bloomberg News. GP-B completed its data collection operations and was decommissioned in December 2010.

NASA's Marshall Space Flight Center in Huntsville, Ala., managed the Gravity Probe-B program for the agency. Stanford University, NASA's prime contractor for the mission, conceived the experiment and was responsible for the design and integration of the science instrument, mission operations and data analysis. Lockheed Martin Corp. of Huntsville designed, integrated and tested the space vehicle and some of its major payload components.

"The mission results will have a long-term impact on the work of theoretical physicists," said Bill Danchi, senior astrophysicist and program scientist at NASA Headquarters in Washington. "Every future challenge to Einstein's theories of general relativity will have to seek more precise measurements than the remarkable work GP-B accomplished."