KAGRA Gravitational Wave Detector, Toyama
Gravitational waves (GW) was introduced from the general theory of relativity by A.Einstein, and its like a ripple of space-time. Nobody has succeeded to directly detect GW as a change of space- time. In our daily life, we never noticed that space and time as a special relation between them. If we could move at the speed of light, we will notice that time could be extended due to the action of moving itself. Unfortunately, we have no technology to carry a human-beings at near the speed of light. On the other hand, we have already succeeded to accelerate an elementally particle, which had known finite life time, almost at the speed of light, and to observe its particle life time was extended. Consequently, space and time do have special relation between them, as it were “structure of space time”. If GWs pass, the structure of space time will change a little bit.
In principle, a Michelson type laser interferometer is used. A laser beam emitted from a laser source will be divided in power at a beam-splitter at a right angle. The split laser beam will be reflected by mirrors that are set away from the beam-splitter at the same distance and come back again to the beam-splitter. At the beam-splitter, they are recombined and interfered with each other. If GWs go through the interferometer, each arm will be extended and shrunk in the opposite phase, and the time that each laser beam takes to travel will be different. Consequently, the interfered fringe between the laser beams will change.
Prof. Rajesh Dubey is one of the very few people in the world who was given the rarest chance to access the interior of the underground experiment area. The underground cryogenic Gravitational Waves detector has the tremendous capabilities of detecting Gravitational Waves at very low seismic notices. He interacted with scientists, researchers and engineers of this extraordinary project to detect Gravitational Waves as an expert.