On February 11, 2016, a group of scientists affiliated with an American collaboration announced that they had made the first direct detection of gravitational waves, a long sought consequence of Albert Einstein’s general theory of relativity.
The announcement sparked celebrations among physicists around the world – and turned out to be extra special for a group of scientists in India because, a week later, Prime Minister Narendra Modi gave ‘in principle’ approval for a gravitational wave detector to be set up in the country. Say this to Bala Iyer and he smiles. “We were working toward the project’s approval and were doing everything to keep moving in that direction, but the actual detection of the waves did help.”
Iyer is the chairman of the Council of the Indian Initiative in Gravitational Wave Observations Consortium, shortened to IndIGO, and currently a visiting professor at the International Centre for Theoretical Physics (ICTS), Bengaluru. In the last two decades, Iyer has worked on modelling the sources of gravitational waves and has made fundamental contributions to their study. He has also been an important player vis à vis LIGO-India, the planned Indian detector. LIGO stands for Laser Interferometer Gravitational-wave Observatory.
“The seed money that the LIGO-India project has asked for is Rs.10 crore,” says Iyer. The Departments of Science and Technology (DST) and Atomic Energy (DAE) took the call on funding the project. “We are expecting the money this year.We had asked for a total of Rs. 1,260 crore in 2012. Now, because of the depreciation in currency values, the amount may differ a little. The Indian government has agreed to the proposal and is discussing with lead institutions on how to put everything into place,” he explains.
Tarun Souradeep, an astronomer at the Inter-University Centre for Astronomy and Astrophysics (IUCAA), Pune, and the spokesperson for IndIGO, says, “We have been assured by the government that work will not stop because of financial reasons. Money will keep coming based on our needs and we hope to get full financial approval for the rest of the funds by 2017.”
A site for the detector
On the question of where the detector might be located, Souradeep says, “We had 22 options, but there are many challenges in selecting a site for the detector as the requirements are stringent. It must be far away from regular noise made by transport, factories, etc., the terrain must be flat, and finally the location must be remote but accessible.”
According to him, the Indian collaboration has zeroed in on two sites – one in the Udaipur-Chittorgarh area of Rajasthan and another in the Marathwada area of Maharashtra. The final location is set to be announced in the next two weeks. In keeping with past incidents, acquiring the land on which the detector will be situated could be a problem – but Souradeep is optimistic. He says they will follow the standard land-acquisition procedures and don’t foresee any objections – not along the lines of those experienced by the India-based Neutrino Observatory.
LIGO-India, like its twin American counterparts, will have two arms joined at a vertex in the shape of an ‘L’. Each arm will be four kilometres long and form one half of an interferometer, an instrument that measures how out of phase beams of light coming through each arm are. In the absence of a gravitational wave, beams reflected through the length of each arm and reconvening at the vertex are in phase and produce no interference pattern. But when a wave passes through, distorting the dimensions of space by a very tiny amount, one beam becomes out of phase with the other and a detector at the vertex registers an interference pattern.
Such a machine will have to be extremely sensitive – enough to catch a distortion in space of the order of 10-21 m. Iyer thinks that it “will take about six to seven years” for it to be fully set up, calibrated, and for the types of mistakes in its readings to be understood, before it can attain full sensitivity and become usable in experiments. “It will be 2023 by when we can get actual results,” according to Iyer.
The American detectors are in Hanford, Washington, and Livingston, Louisiana. Their sensitivities were hiked to an ‘Advanced’ configuration in 2014. And the proposed LIGO-India project aims to move one Advanced LIGO detector from Hanford to India.
The LIGO Lab, the body responsible for operating the LIGO detectors and which oversees the pertinent R&D, will provide the complete design and all the key detector components to India. For their part, Indian scientists will be responsible for securing the infrastructure to install the detector at the chosen location, installing it and finally commissioning it – at a total cost of Rs.560 crore, according to Iyer. Once it goes live, the detector will be operated jointly by IndIGO and the LIGO Lab, and become part of a global network of gravitational wave detectors, including the two in the US and one in Italy.
The lead institutes from the IndIGO Consortium that will be a part of LIGO-India are IUCAA; the Institute of Plasma Research (IPR), Gandhinagar; and the Raja Ramanna Centre for Advanced Technology (RRCAT), Indore. Along with the DAE and DST, they will collaborate with the American National Science Foundation (NSF), the California Institute of Technology (Caltech), and the Massachusetts Institute of Technology. And the collaborations will be mediated via memorandums of understanding with the funding agencies and institutions. The national government is currently talking to the institutions on how to get everything in place.
The principal motivation for an Indian detector is that most of the other existing detectors lie on almost the same plane, in the northern hemisphere. As a result, they’re not suited for observing some parts of the southern sky as well as being unable to pinpoint sources of gravitational waves in the universe accurately. An Indian detector would ‘stretch’ this network out, widening its eyes, so to speak. “Multi-messenger astronomy can … be feasible once we have a better localisation of the sources,” clarifies Iyer.
The Indian LIGO story stretches dates back to the 1980s, when a group of physicists from, but not limited to, IUCAA and RRI suggested to the government of India that an experiment be set up in the country. While the modeling work took off in full swing, a request for funds in 1990 was met with silence. But the group was not discouraged and continued its work. Then, Rana Adhikari, a professor of physics at Caltech, proposed that India renew its pursuit of an Indian detector in a talk at IUCAA in 2007. Iyer says, “That got a group of us thinking and we formed the IndIGO Consortium in 2009.”
Referring to the existing detectors lying on a common plane, Iyer explains that India – as part of an international group – joined in the efforts to build a detector in Australia that the two countries could then jointly operate. However, in 2011, Australia backed out of the project citing a lack of funds.
Abhay Ashtekar, a theoretical physicist at Pennsylvania State University, and his research group spoke to the Indian government about India hosting the detector and, in June 2011, the plans for LIGO-India were kicked off. By October, IndIGO had been tasked with putting together a roadmap within a month – the short deadline because the 12th Five Year Plan was getting ready. Then, in November, officials from the DST and the DAE met to identify the lead institutes.
Finally, the proposal went through four reviews by the NSF, as well as repeated scrutiny by members of the international LIGO collaboration apropos India possessing the expertise needed to install the detector, the financial ability to house it, etc. Next, the NSF had to get an approval from the National Science Board to make India the new host country. And at long last, “the approval by the government of India finally came on February 17 this year, after gravitational waves were detected” for the first time, says Iyer.
Papiya Bhattacharya is a science writer based in Bengaluru.