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General Relativity

May 7, 2012

When it comes to describing gravity, Albert Einstein is the heavyweight champ. So far, every test has confirmed his theory of gravity, which is known as General Relativity.

Published more than a century ago, the theory said that gravity wasn’t a “force” acting instantly across the universe, as Isaac Newton had envisioned it. Instead, any object with mass — from a pill bug to a galaxy — “warped” the spacetime around it.

A pill bug’s effect is negligible, but the effect of more massive objects could be profound. A star, for example, should curve space in such a way that it would deflect the light of more-distant stars passing by it. This effect was confirmed during a solar eclipse in 1919. That made Einstein an international star — and put him at the pinnacle of gravitational theory.

Since then, General Relativity has been confirmed in many other ways. One of the first was a small shift in Mercury’s orbit around the Sun — it’s caused by the Sun warping the space around it.

General Relativity also predicts a gravitational redshift, in which the gravity of a star stretches the lightwaves that leave its surface — an effect seen with white dwarf stars. And it predicts that the passage of time is different for observers in different gravitational fields. That’s been confirmed by flying atomic clocks in high-altitude airplanes — and it’s a key factor in the success of a bit of modern technology. More about that tomorrow.


Script by Damond Benningfield, Copyright 2012


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