mark me as brainlistExplanation:One of the landmark discoveries of the twentieth and twenty-first centuries so far is the discovery of Gravitational Waves (GW). The EXISTENCE of GW was predicted exactly 100 years ago by Albert Einstein based on his General Theory of Relativity. It is interesting to KNOW that he did not believe that the GW will be discovered in the laboratory. Why? It is because the amplitude of the GW will be so small (10-21m) that no experiments will be able to measure this small displacement, corresponding to about 1 millionth of the diameter of proton. The beauty of the theory made the experimentalists design appropriate experiments to detect such a small displacement. For the last 25 years, about 1000 scientists from more than 25 countries are actively involved in this task. In this team, there are 37 Indian scientists working in various academic and research institutions in India. On 14 September, 2015, scientists were able to detect the arrival of a GW that originated about 1.3 billion years ago. They were able to observe GW using the facilities at two Laser Interferometer Gravitational Observatories (LIGO) in the US. They got the wave pattern exactly as predicted by Albert Einstein using his General Theory of Relativity. Einstein showed that the space time surrounding a massive object is curved. And any particle moving in the vicinity of this object will trace a curved path instead of a straight line. The curved path taken up by the particle will appear as though it is being attracted by a force from the massive object. This generates what is called gravitational field. The curvature of the space surrounding a massive object will depend on the mass of the object. Any significant event in the universe will generate disturbances in the gravitational field and will produce GW. There are 37 Indian scientists from IISER Thiruvananthapuram and Kolkata, IIT Ahmedabad, TIFR, Institute of Mathematical Sciences, Chennai, Inter University Consortium for Astronomy and Astrophysics ( IUCAA) Pune , Raman Research Institute , Bangalore and Indian Institute of Science, Bangalore, who are active PARTICIPANTS in this global initiative of LIGO experiments. The machines that gave scientists their first-ever glimpse at GW are the most advanced detectors ever built for sensing tiny vibrations in the universe. The two US-based underground detectors are known as the Laser Interferometer Gravitationalwave Observatory or LIGO for short. India is aiming to get the world’s third LIGO at an estimated cost of 1,000 crore. As part of the ongoing Indo–US cooperation in science and technology, America will provide India with nearly $140 million worth of equipment. Professor C. S. Unnikrishnan from TIFR is the leader of Indian LIGO experiment. He is one of the 137 authors of the research paper published in Physical Review Letters in February 2016. It is hoped that the Indian LIGO will be functional within a couple of years. The GW opens up another window for astronomy. The observatory will be operated jointly by IndIGO and LIGO and would form a single network along with the LIGO detectors in the USA and Virgo in Italy. The design of the detector will be identical to that of the Advanced LIGO detectors in the USA.