NASA發射空間探測器 挑戰相對論

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, project 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 program`s chief scientist, Francis Everitt, a theoretical physicist from Stanford University, where the mission was first conceived in 1959, then funded in 1964. Not until the 1990s were engineers from Stanford and NASA 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, making them the most accurate gyroscopes ever built.

"There are two reasons why these are the most perfect gyroscopes. They`re the most perfect spheres (ever manufactured) and going into space allows you to make enormously more accurate gyroscopes than is possible on the ground," Everitt said.

The satellite, which was inserted into a polar orbit, will spend two months getting ready, then 16 months making measurements.

Mission scientists hope they will not only have proof about Einstein`s theory, but a precise number for calibrating the effect.

Although the effect is hard to measure around something Earth-sized, it can be quite dramatic around something as massive as a black hole, where this frame dragging may account for quasars, the most violent eruptions of energy ever detected.

Copyright 2004 Reuters.-------4/21 CNN.com