When the whole world goes about its mundane activities, somewhere far away, at a very large distance from the earth, several millions of light-years away, comes a mild quake, practically negligible, due to the collision of two massive black holes, wobbling the entire space around it, including the sun, the moon, stars, and galaxies. It stretches and compresses everything that comes in its way by a very small magnitude. Strange? Yes, definitely at first, but it was predicted theoretically more than a century ago by the genius, Professor Albert Einstein, in his theory of general relativity. Thus, began a quest to understand these disturbances called gravitational waves (GW). Measurement of these faint disturbances requires sophisticated and precise equipments namely LIGO (Laser Interferometer Gravitational-wave Observatory), Virgo, and LISA (Laser Interferometer Space Antenna). Several countries are collaborating in this venture and India is taking strides in the right direction by initiating many scientific experiments and research activities in this dimension. Through the majestic LIGO-India project, many hidden mysteries about the universe are expected to be unravelled.
What is LIGO?
The Laser Interferometer Gravitational-wave Observatory, abbreviated as LIGO, is an observatory set up to detect the gravitational waves, which are ripples in the fabric of spacetime, due to the collision of the two large masses in the space, either two Neutron star or Black Hole, or two large masses spiraling around each other, explosion of a star, etc. These disturbances (energy) created are transmitted in all directions in space, even to the deepest corner of the universe where humans are unable to reach, even through a telescope. Gravitational waves are non-mechanical waves, hence they do not require any material medium to travel, also these waves cannot be viewed through any instrument, as they are not part of the electromagnetic spectrum. Hence LIGO was decisive in proving the presence of the gravitational waves. With its L-shaped perpendicular arms spread over 4 km and maintained at low pressure or ultra-high vacuum, LIGO uses a powerful laser beam as the source of light. This beam of light is split at the intersection of two arms, in an arrangement such that the reflected light waves interfere destructively, measuring the stretching and compression of the spacetime, which is comparable to the size of the proton.
LIGO-India which is one of India’s mega-science projects received ‘in principle’ approval by the Union Cabinet to build an indigenous gravitational wave detector observatory, LIGO India, on February 17, 2016, soon after the detection of the first gravitational wave on February 11, 2016. This project is piloted by the Department of Atomic Energy (DAE) and the Department of Science and Technology (DST) with the Memorandum of Understanding (MoU) with the National Science Foundation (NSF), USA. LIGO-India is a collaborative venture of the LIGO Laboratory, operated by Caltech and the Massachusetts Institute of Technology (MIT), and three Indian institutes, namely the Raja Ramanna Centre for Advanced Technology (RRCAT), The Institute for Plasma Research (IPR), the Inter-University Centre for Astronomy and Astrophysics (IUCAA).
Why does India or the world need these collaborations?
Through global chains of gravitational wave detectors, we can precisely measure any gravitational wave to a high degree of accuracy and extract the best information. Thus, by adding more detectors it is possible to locate the source of gravitational waves, test theories on gravity, space and time, which may answer many questions about the universe and matter that is currently hidden from us. Although there are three LIGO detectors worldwide, two at Hanford, and one at Livingston, VIRGO in Italy (said to be LIGO’s cousin), there is a need to localise the source of the GW, this can be achieved by adding more detectors and working simultaneously on it across the globe, thus extracting maximum information from the GW. The fourth detector built at Kagra, Japan, will be functional within a year. Fifth LIGO, advanced LIGO (aLIGO), is estimated to commission in India in the year 2025, acquisition of the site for the construction of Advanced LIGO (aLIGO) is already selected; Hingoli District of Maharashtra.
The hardware required for the construction of the LIGO interferometer, technical data of its design, installation, commissioning, training, and assistance with installation, and design of the vacuum system will be provided by the LIGO laboratory in collaboration with the USA, UK, Germany, and Australia. Three Indian institutions, mentioned above, are sharing the responsibility of the required infrastructure to operate the interferometer, labour, material, and supplies for installation, commissioning, and operating. India builds high precision, low-pressure (high vacuum) tubes of 4 km Michelson Interferometer with enhanced cavities and aims to detect the space strain, which will measure the change in arm-lengths as small as 4×10-20m. This tube holds about 10 million litres of Ultra High Vacuum . The LIGO detectors are the most precise and accurate physics apparatus till today.
aLIGO will serve various benefits to India since LIGO needs the construction of the world’s largest ultra-high vacuum facility, which in turn gives the Indian industries an unprecedented advantage gearing up their technology and advancement to match the world standard. Also, aLIGO needs an academic-industry research partnership to venture into this project, which is evident in the past in the USA and Europe. This, indeed, will boost the confidence in Indian industries in several breakthroughs and upcoming new technology startups. Secondly, this mega project will help to trigger the interest in the students and student researchers in the fields of astrophysics, astronomy, and gravitational waves, which will be the new way of viewing and studying the universe. As the LIGO India spreads its roots firmly on the Indian soil, an optimum benefit can be availed by the student community and to popularise the GW field among the student community in future, the data collected by the detector can be made available for the students for their thesis or projects in the college or research institute, through this process students and researchers can be connected to the field of gravitational waves at a very young age. Also, having a field visit and interacting with the gravitational waves scientist at the LIGO site will churn the interest of gravitational-wave scientists of the next generation.
In the Indian context, LIGO will revolutionise the gravitational wave scientific community in India. Indian gravitational wave community had played a vital role in the detection of the first gravitational waves in the year 2016. Thus, as part of the preparation to welcome the new field in India, the first round of the discussion took place in the year 2007 at the International Conference in Gravitation and Cosmology at IUCAA (Inter -University Centre for Astronomy and Astrophysics). In a subsequent meeting in August 2009 at IUCAA, a consortium of Indian researchers called IndIGO was formed (who are experts in the relevant field). Therefore, India is in a good position in the field of GW, we have discovered the field before it could completely blossom and go out of our hands.
Due to the proactive involvement of the members of the Indian consortium, IndIGO, the number of members has increased from 14 in 2010 to more than 120 members today, and 3 experimenters in 2010 to more than 56 experimenters today from various research institutions of India. This is a classic example of exploring the field. The data mentioned above is before the announcement of the construction of indigenous LIGO, after commissioning the aLIGO in India, the members of the Indian Gravitational-wave community may increase by manifold in the following decades, resulting in major research in India. LIGO India is possible by precisely integrating many fields and advanced technologies, such as Laser physics, quantum gravity, general relativity, optical engineering, sensor technology, controlled system, cloud computing, optical technology, quantum metrology, etc.. Advancement in all branches are expected to match the advanced LIGO standards. To do so, scientists and engineers must explore new ways of advancement in their respective fields. These advances by the Indian scientific community will, directly and indirectly, have a positive impact on the social status of the nation.