Two years ago, I blogged about how Einstein's E=mc² was supported by experimental evidence. Well now an international group of astronomers have observed evidence that supports another prediction from Einstein's General Relativity from 1915.

The video below explains the experiment, so I'll give some background and a quick explanation. When massive stars die and explode as supernovae, they leave behind an ultradense object called pulsars. One such stellar ruin, affectionately known PSR J0737-3039A/B and lying about 1700 light years away from us, is the only known double pulsar, meaning there are two objects that orbit each other. Actually, they are so close to each other the whole system can fit inside our sun. As pulsars rotate, they emit very powerful radio waves which we can detect on Earth, and that's what allowed the astrophysicists to test Einstein's theory.

What Einstein's theory predicted is that in a system like a double pulsar, the two objects will affect each others motion. The change in motion is a slow one and called a "precession". You can see something similar at home: spin a top but make it spin slightly off-vertical. You'll see the axis of the top rotate slowly, like the image to the right. The question is: can we observe such precession in PSR J0737-3039A/B? Yes we do.

A paper just published in Science magazine describes how such a precession was observed. But don't bother with the paper, just watch the video below.