Slashdot Mirror
Lab Tuned to Gravity's 'Ripples'
Krishna Dagli writes "One of the great scientific experiments of our age is now fully underway. Success would confirm fundamental physical theories and open a new window on the Universe, enabling scientists to probe the moment of creation itself. The experiment is trying to detect ripples created in the fabric of space-time that sweep out from merging black holes or exploding stars and detection would be a final test of Albert Einstein's General Theory of Relativity. "
Right now we are uncertain of the exact speed of gravity.
We are always "uncertain" about the exact value of any physical quantity, because no quantity can be measured with infinite precision.
There is very little doubt that the speed of gravity is equal to the speed of light.
Some measurements resulted in speed between 0.8 and 1.2 times the speed of light
The Taylor-Hulse pulsar measurements have measured the accuracy of that speed to within a few percent, much better than the 20% figure you cite. Furthermore, most of the gravitational physics community is convinced that the experiment mentioned did not measure the speed of gravity (as the Wikipedia article alludes to).
If the speed of gravity is greater than the speed of light, does that violate the general relativity?
Yes. It also violates special relativity and the laws of cause and effect.
It is important that we find what gravity is, because if it is a wave of particles, then maybe there is a possibility to find a way to shield gravity away.
Gravity being "a wave of particles" does not imply that it can be shielded, and gravitational wave detectors are unlikely to tell us anything about that issue.
Even if it were possible to "shield gravity" (very unlikely), it is almost certainly impossible to do it with any realistic technology, because we already have a thorough understanding of gravity on the scales that our technology can reach in the forseeable future.
A little realism: LIGO and its kin may teach us something new about gravity near neutron stars and black holes, but the most likely outcome is that it will simply serve as a telescope to probe astrophysical phenomena not detectable in visible light. It is very farfetched to think that it will lead to antigravity or any Star Trek type applications.
I am surprised nobody mentioned Einstein@home - http://einstein.phys.uwm.edu/.
This experiment uses distributed computing to process their results,
and you can participate.