Thursday, October 28, 2004

Men in Geek

Okay, you've gotten used to the ideas of black holes and extrasolar planets. You've heard that we don't actually live in a universe of three spatial dimensions plus time but in four-dimensional spacetime. You may even have gotten a sense of the General Theory of Relativity, which describes gravity as the result of the warping of spacetime in the presence of mass.

Now go a step further.
Earth's spin warps space around the planet, according to a new study that confirms a key prediction of Einstein's general theory of relativity.

After 11 years of watching the movements of two Earth-orbiting satellites, researchers found each is dragged by about 6 feet (2 meters) every year because the very fabric of space is twisted by our whirling world.
It's called frame-dragging, and like black holes, an expanding universe, gravitational lensing, and more, the idea for it was derived from general relativity well before actual observations proved it.
Here's how it works:

Any object with mass warps the space-time around it, in much the same way as a heavy object deforms a stretched elastic sheet, explained study leader Ignazio Ciufolini of the Universita di Lecce in Italy.

If the object spins, another distortion is introduced, "in the same way as the elastic sheet would be twisted by a spinning heavy wheel on it."

If the space around Earth is being frame-dragged, then satellites ought to be caught up in the deformation, scientists reasoned. Imagine how a second object on the elastic sheet would be moved by the scrunching motion created as the sheet is deformed.
It was that extra motion that the team detected in the satellites. Although the results have a 10% margin of error, the apparent agreement with theory is so close (99% of the predicted value) that it's a pretty convincing find.

Einstein wins again. Or, I suppose we should say, nature wins again, because the reason these predictions could be made is that nature acts consistently and does not contradict itself.

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