Gravitational wave is a concept introduced by Einstein in 1916 as part of his general theory of relativity. We are familiar with the ripples being created when a boat travels through water. Gravitational waves can be conceived as ripples created because of the acceleration of mass or an object in space. They are caused during collusions of black holes, collapse of supernovae, merger of white dwarf stars etc. They are considered to be the most disastrous, violent and powerful activities happening in the universe releasing huge quantum of energy.
Though the theory of relativity was proposed in 1916, proof of existence of gravitational waves could be identified only in 1974. In that year, two scientists, Kip Thorne and Rainer Weiss, doing research in the Arecibo Radio Observatory in Puerto Rico identified two thick and heavy stars orbiting around each other. It was this kind of activity that was proposed by Einstein to generate gravitational waves. After observing the changes in the orbits of the two stars for around eight years, the astronomers identified that the stars were approaching each other exactly at the rate proposed in general theory of relativity. After continuous observations of over 40 years, and identification of further similar effects, it is proven that gravitational wave is a reality.
General theory of relativity states that mass has the capability to distort space and time. It was suggested that gravitational waves would travel through the universe at the speed of light. It was also indicated that the ripples would contain information about their origin, early universe and gravity. However, such waves could be identified for the first time only on September 14, 2015, around 100 years after suggestion of the idea by Einstein. It was identified by the researchers with the aid of Interferometer in the Laser Interferometer Gravitational-Wave Observatory (LIGO) in the United States. LIGO is an observatory dedicated for the research on gravitational waves. The waves identified by LIGO were originated 1.3 billion light years back by the collusion of two black holes.
As mentioned earlier, gravitational waves are highly violent carrying unimaginable level of energy. However, by the time they reach the Earth, they become less damaging due to the time lag. The energy identified by LIGO was thousands of times lesser than the nucleus of an atom. Identification of gravitational waves is considered as one of the greatest scientific achievements. Realizing the importance of the achievement, the Royal Swedish Academy of Sciences awarded the Nobel Prize in Physics 2017 to Rainer Weiss(one half) and the other half jointly to Barry C. Barish and Kip S. Thorne for their contributions to the LIGO detector and identification of gravitational waves. Saraswaty Supercluster- Supercluster Discovered by Indian Scientists