The announcement that the direct observation of gravitational waves has been achieved by the Laser Interferometer Gravitational-Wave Observatory, or LIGO, ushers in a new era in astrophysics. It confirms one of Albert Einstein's most startling hypotheses. It was a century ago that Einstein, through his General Theory of Relativity, claimed that gravity worked in waves. In another first, LIGO also directly detected binary black holes. In fact, it was the coalescence of two black holes into one larger black hole some 1.3 billion years ago that set up the gravity wave detected by LIGO on September 14, 2015. Again, this observation confirms several hypotheses made by theoretical physicists decades and more ago.
It was an international initiative. While the two working facilities are in the US, data related to the "chirp" that indicated a gravity wave were first flagged by an Italian scientist in Europe. Indians played important roles, working directly at LIGO, and also as part of the 16-nation collaboration that examined and validated data. Indians also played key roles in developing the essential theory underpinning LIGO. Astrophysics giant Subrahmanyan Chandrasekhar first conceptualised neutron stars and black holes, back in 1931. C V Vishveshwara did important work on the structure of black holes and the gravitational frequencies of their emissions. B S Sathyaprakash and Sanjeev V Dhurandhar outlined how "noise" could be filtered out of data. Bala Iyer led a group that computed likely wave forms and validated the LIGO data.
The dimensions of the new research and fresh discoveries that could follow from this breakthrough can only be guessed at. Thus far, astrophysicists had been able to observe the universe with optical radiation (visible light, by using telescopes since Galileo's time), in infrared and ultraviolet rays, and across the spectrum of electromagnetic radiation with gamma rays, x-rays, long radio waves etc. Being able to use gravitational waves opens up new observational windows. Gravity itself has never been integrated into quantum theory and a better understanding of this force could help put together the so-called "Grand Unified Theory" which Einstein, Abdus Salam and other great physicists have long sought. Gravity waves acted in unusual ways at the very beginning of time. As the volume of space that LIGO can examine grows, it will reach further back in time since the signals will come from the more distant past. This will help understand the "Big Bang", when the universe began.
LIGO can now examine space up to a limit of a sphere with a radius of about two billion light years. It is being upgraded to thrice that range. In this context, it is important to set up laboratories outside the US (and ultimately in space). More facilities, with greater distances between them, will help improve detection confidence and also aid in triangulation of gravity wave signals to exactly identify origins. The IndIGO group (the Indian Initiative in Gravitational-wave Observations) has been lobbying for a LIGO facility since 2009. The US LIGO is willing to provide some equipment while IndIGO can build the facilities and design as well as fabricate much equipment itself. IndIGO has even reportedly found suitable sites and setting this up would be a big boost for India's science community. But the necessary clearances and budgets have been hanging fire for years. It is to be hoped that the LIGO success will help expedite such clearances and thus enable India to play a lead role in future research in this big new area.
