Nasa launches Einstein Gravity Probe B

Nasa launches Einstein Gravity Probe B
REUTERS[ THURSDAY, APRIL 22, 2004 02:24:02 AM ]

CAPE CANAVERAL: Forty-five years in the making and 24 hours late, Nasa launched a $700 million satellite into orbit on Tuesday to test Albert Einstein's general theory of relativity.

The Gravity Probe B, one of the most precise scientific instruments every built, was carried aloft by a Boeing Co Delta 2 from the rocket range at California's Vandenberg Air Force Base. A day earlier, launch directors from Boeing and Nasa's Kennedy Space Center in Florida scrubbed the launch in the final minutes of the countdown when there was a problem loading software.

Einstein developed his mind-bending theories of relativity in the early 20th century, and today those theories are generally accepted, especially as they find their way into applications such as medical scanners and the Global Positioning System.

Among the most exotic of Einstein's predictions was that massive bodies ?- planets, stars or black holes ?- actually twist time and space around as they spin, much like the winds of a tornado. Other tenets of general relativity have been tested, such as the warping of time and space by massive bodies, but the twisting effect, known as frame dragging, has never been put to the test, scientists said. If Einstein is right, scientists say, the satellite should detect that small bits of time and space are actually missing from each orbit, something indiscernible to orbiting astronauts but measurable nonetheless.

"I call it the missing inch," said the programme's chief scientist, a theoretical physicist from Stanford University.

Not until the 1990s were the engineers and scientists able to build a satellite precise enough to make the measurement. The heart of the 3.5-tonne satellite is a container holding four spheres the size of ping pong balls that will be chilled to near absolute zero and spun 10,000 times a minute, to be the most accurate gyroscopes.