WEINSTEIN: We feel like gravity is a very strong force because it’s the one that’s holding us down on the Earth. When we jump up we feel gravity pulling us down pretty strong. But actually gravity is an extremely weak force. It’s only strong at the level of people and planets and the orbits of the Moon around the Earth and the Earth around the Sun.
Alan Weinstein is a physicist at Caltech, and a member of an international collaboration that’s hunting for gravitational waves — ripples in spacetime produced by moving objects. Scientists are pretty sure that gravitational waves exist, but they haven’t yet actually seen them. That’s because gravity is the weakest of the basic forces of nature. Because of that, gravitational waves are tiny — even those produced by such massive objects as exploding stars or the mergers between two stellar corpses known as neutron stars.
If such a pair of neutron stars were about 50 million light-years from Earth, by the time their gravitational waves reached us, their effect on detectors would be much smaller than a proton.
David Reitze, the leader of the collaboration, explains:
REITZE: Another way of saying that would be, if you were trying to measure the distance from here to the nearest star, to that level of precision, you’d be able to do it to within the width of a human hair. That’s the kind of precision that we need to measure, and it just has to do with the fact that gravity is a very weakly interacting force.
We’ll have more about gravitational waves tomorrow.
Script by Damond Benningfield, Copyright 2011
For more skywatching tips, astronomy news, and much more, read StarDate magazine.