Einstein’s Theory Rockets Into Orbit
After 45 years of development and delays, NASA’s Gravity Probe B satellite was launched into orbit Tuesday morning to test a key prediction of Albert Einstein’s general theory of relativity.
The 6,800-pound, $750-million spacecraft was placed in a 400-mile-high polar orbit by a Boeing Delta 2 rocket launched from Vandenberg Air Force Base at 9:57 a.m. The craft, about the size of a van, separated from the rocket 75 minutes later.
“The solar arrays are deployed, and we have received initial data that indicates all systems are operating smoothly. We are very pleased,” said program manager Rex Geveden of NASA’s Marshall Space Flight Center in Huntsville, Ala.
“This is a great moment and a great responsibility, the outcome of a unique collaboration of physicists and engineers to develop this near-perfect instrument to test Einstein’s theory of gravity,” said Stanford University physicist Francis Everitt, the principal investigator.
Everitt and his colleagues will spend the next two months calibrating the precision gyroscopes on board the satellite, then another 18 months conducting the experiment that was first conceived in 1959 during the Eisenhower administration, only a year after the United States had launched its first satellite.
Einstein’s theory states that gravity is a distortion in the fabric of space caused by massive objects. Earth, like a bowling ball dropped on a rubber sheet, stretches the invisible fabric of space and causes smaller objects to move toward it.
That portion of the theory was confirmed by Gravity Probe A, launched in 1975.
But the theory also says that as the Earth spins on its axis, it tends to twist the fabric of space around it slightly. Gravity Probe B is designed to test that.
It took a long time to develop the instruments needed to measure the distortion and to persuade NASA to launch it. The space agency canceled the mission at least seven times.
The heart of the satellite is a perfectly shaped quartz sphere, about the size of a pingpong ball, that is electrostatically floated in a cryogenic chamber and spun at 10,000 revolutions per minute. The craft carries three identical backup spheres.
The spinning sphere is a highly precise gyroscope, purportedly the most accurate scientific instrument ever built. Researchers hope it will detect the twisting in the fabric of space, deflecting slightly in response to it.
A Superconducting Quantum Interference Device, or SQUID, will detect any changes in the sphere’s axis of rotation and send the results back to Earth.
The bulk of the satellite is made up of coolant to maintain both the sphere and the SQUID at a temperature near absolute zero -- about minus 460 degrees Fahrenheit.
