Einstein was right: Scientists say satellites pulled slightly...

Einstein was right: Scientists say satellites pulled slightly off their orbits show that the earth is indeed twisting the fabric of space-time as it rotates.

An international team of scientists put together by NASA says the findings are the first to directly measure and prove an important aspect of Albert Einstein's general theory of relativity - that a rotating body warps and twists the "fabric" that combines the three dimensions of space and the fourth dimension of time.

"As the earth turns, it is actually twisting space-time with it," said Michael Salamon, a physicist at NASA in Washington. "Near earth, the twisting is greater.

"This twisting of space-time, which is also referred to as frame-dragging, has never been directly observed before," he said.

"This is the first real, solid, direct evidence we have for the twisting of space-time caused by the spinning of a rotating body."

Erricos Pavlis of the Joint Centre for Earth System Technology at NASA and the University of Maryland and colleagues observed two satellites orbiting the earth and found that they did shift as the planet pulled on space.

"We measured the distance from the earth to the satellite with the accuracy of millimetres," Mr Pavlis said. Their research was reported in the journal Nature.

The Laser Geodynamics Satellite I or LAGEOS I, a NASA spacecraft, and LAGEOS II, a joint NASA/Italian Space Agency satellite, are basically hunks of metal covered with reflectors that make them easy to follow and measure from the ground.

Their butterfly-shaped orbits are meant to simulate the movement of a spinning gyroscope. Einstein's theory predicts that a nearby spinning body - such as the earth - will pull on space and cause a gyroscope to shift slightly on its axis.

There is no proof that some other force is not acting on the satellites, Mr Pavlis said, but it is unlikely.

"It would have to be a very smart force to exactly mimic general relativity," he said.

Mr Pavlis says the so-called "frame-dragging effect ... is like what happens if a bowling ball spins in a thick fluid such as molasses".

"As the ball spins, it pulls the molasses around itself," he said.

"Anything stuck in the molasses will also move around the ball. Similarly, as the earth rotates, it pulls space-time in its vicinity around itself. This will shift the orbits of satellites near earth."

--Reuters/AFP

Dave R.