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.
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.