LIGO-India Project

Table of Contents

Context: Laser Interferometer Gravitational-Wave Observatory (LIGO project) has been given final clearance by the Union Government.

What is LIGO?

LIGO is an international network of laboratories that aim to detect ripples in spacetime (gravitational waves) produced by the movement of large celestial objects like stars and planets.
Spacetime encapsulates the current understanding of how gravitation works. It was first postulated in Albert Einstein’s General Theory of Relativity.

The LIGO-India project will be set up in Hingoli district of Maharashtra and will start scientific runs from 2030.
The detector will be built as part of LIGO-India collaboration. This project will be collaboration between Ligo-USA, India, Germany, Australia and U.K.
Lead institutes: Institute of Plasma Research (IPR), Gandhinagar, Inter-University Centre for Astronomy and Astrophysics (IUCAA), Pune, Raja Ramanna Centre for Advanced Technology (RRCAT), Indore.
Funding: The project will be funded by Department of Atomic Energy and Science and Technology, Government of India.

LIGO facility comprises of two 4-km-long vacuum chambers, built perpendicular to each other. Highly reflective mirrors are kept at the end of the vacuum chambers.
Light rays are released simultaneously in both the vacuum chambers. They hit the mirrors, get reflected, and are captured back.
Under normal circumstances, the light rays in both the chambers would return simultaneously. But when a gravitational wave arrives, one of the chambers gets a little elongated, while the other one gets squished a bit.
Due to this effect, light rays do not return simultaneously, and there is a phase difference. The presence of a phase difference marks the detection of a gravitational wave.
Need for Multiple LIGO detectors:
- The instruments LIGO facilities are so sensitive that they can easily get influenced by events like earthquakes, landslides, or even the movement of vehicles, to produce a false reading. Multiple observatories will revalidate the signals.
- Since the chances of two observatories, located in different geographies, producing the exact same false reading are very low, it will help in improving the quality and accuracy of information.

The project has the potential to transform India into a global site of gravitational physics research, aiding training and the handling of precision technologies and sophisticated control systems.
The project can cement India’s reputation for successfully running an experimental Big Science project in the world.
A cutting-edge science facility, such as the one at LIGO, will have huge spin-off benefits for its science and technology sector.

Newton’s law of gravitation: Newton postulated that the force that makes any object fall to the ground also makes heavenly bodies go around in their orbits.
- This phenomenon was occurred due to the fact that every celestial body exerted an attractive force on every other body in the universe.
- According to the mathematical formulation, the strength of this attractive force was directly proportional to the masses of the two bodies and inversely proportional to the square of the distance between them.
- Drawbacks: The theory could not find the reason for the existence of the attractive force between any two bodies.
  - According to Newton’s theory, gravitational force seemed to be propagating instantaneously, over any large distance. This was proven wrong by Einstein’s Special Theory of Relativity.
  - Special Theory of Relativity had proven that nothing could travel faster than the speed of light. Newton’s gravitational equation failed to factor time.

Einstein’s General Theory of Relativity: In his General Theory of Relativity, Einstein proposed that spacetime (space and time were not independent entities) was not just a passive backdrop to the events happening in the universe.
- Spacetime interacted with matter, was influenced by it and in turn, also influenced events. It was comparable to a heavy object placed on it, and curls around it.
- The curvature in spacetime was the reason for smaller bodies in the vicinity feeling the gravitational pull.
- Gravitation is nothing but a curvature in spacetime. Since the spacetime itself is curved around the heavier mass, other nearby objects find themselves revolving around the central mass.
- Heavier the central mass, steeper and bigger is the curvature in spacetime, and stronger and more extended is the gravitational field.

Gravitational Waves are ripples in spacetime that are produced by moving objects, especially celestial. They can be compared with ripples in water.
Because these are ripples in spacetime, gravitational waves have the effect of causing a temporary deformation in a body when it comes in contact.
When a gravitational wave passes the Earth, the Earth is squeezed in one direction, and bulges in the perpendicular direction.
This deforming effect of gravitational waves is extremely tiny, and hence it could not be experimentally verified for 100 years.
Experimental detection: The first ever gravitational waves were detected in 2015, by the two US-based LIGO detectors, produced by the merger of two black holes.