NEW SEARCH FOR GRAVITATIONAL WAVES

A more sensitive Ligo (Laser interferometer gravitational-wave observatory) is progressing rapidly and will start scanning the sky in summer 2015 searching for gravitational waves.
http://www.bbc.co.uk/news/science-environment-29168676

The first generation of Ligo ran between 2001 and 2010 and saw nothing. Professor AlbertoVecchio from the School of Physics and Astronomy of the University of Birmingham said: 'Advanced Ligo will be sensitive to a factor of 1,000 in the volume that we were observing with initial Ligo, and that is the sphere of volume where we expect to see a few gravitational waves'.

Ligo operates by beaming a high power laser beam into a splitter that divides the beam into two parts. Each part is then directed towards two 4 km tunnels perpendicular to each other. A mirror at the end of the tunnels reflects the rays back into a detector where they are recombined. Since both tunnels are equally long, when the two halves meet in the detector the original signal shows no pattern. But if a gravitational wave was passing through the Earth, a pattern would be observed.

Potential sources of gravitational waves are supernovae, fast spinning neutron stars, or the collision of black holes and neutron stars orbiting close to each other.

Comment: Observation of gravitational waves would be an important test for the verification of the theory of gravity in Einstein's general theory of relativity.