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LIGO detects whispering Gravitational Waves Einstein predicted 100 years ago


"Don't underestimate the power of the dark side"- Darth Vader had cautioned his son Luke in a Star Wars film.

Had Darth Vader been an astrophysicist, he would have been accurate, as the newest discovery of the existence of gravitational waves by the advanced Laser Interferometer Gravitational Wave Observatory or LIGO has taken up the world by storm.

Gravitational waves

For the scientific community this is definitely a much sought-after milestone, one that scientists have been inching closer to, ever since Albert Einstein gave the Theory of Relativity a century ago.

We all have heard and read about the Big Bang Theory and how it led to the origin of life. The faint tone detected by LIGO, physicists say, are the first direct evidence of the ripples created by gravitational waves in the space-time continuum.

What makes the discovery even more thrilling for us Indian is the significant contribution of a group of Indian scientists, from top research centers and labs in Mumbai, Pune and Bengaluru who provided crucial research for the worldwide experiment.

According to news reports a team led by Bala Iyer at the Raman Research Institute in collaboration with scientists in France, had developed the mathematical calculations used to model gravitational wave signals from orbiting black holes and neutron stars. [Read here]

Sanjeev Dhurandhar at IUCAA led another group that had carried out stellar work related to developing data analysis techniques to detect these weak gravitational wave signals buried in the detector noise.

'We can now listen to the stars', claim scientists

What are gravitational waves?

Gravitational waves are freely propagating oscillations in space-time, as put forward by Albert Einstein in his General Theory of Relativity which predicts that accelerating masses produce gravitational waves.

During various astrophysical phenomena, like the collision and merger of two black holes, gravitational waves are released, which carry enormous amount of energy with them.However, the interaction of these waves with matter is extremely feeble and hence the challenge was to detect them through experiments.

Although gravitational waves were not directly detected earlier, observation of the orbital decay of binary neutron stars (pulsars) had provided indirect evidence of their existence.

Space-time and continuum

In 1906, soon after Albert Einstein announced his special theory of relativity, his former college teacher in mathematics, Hermann Minkowski, developed a new theory related to the physical constructs of space and time.

According to Minkowski, space and time have to be combined into a new mathematical entity called 'space-time', because the equations of relativity show that both the space and time coordinates of any event must be combined mathematically in order to accurately describe what we see.

Also, he had said that as space consists of 3 dimensions, and time is 1-dimensional, space-time must, therefore, be a 4-dimensional object.

The term 'continuum' refers to the fact that there are no missing points in space or instants in time. Hence, physicists now routinely refer to the world, present in a 4-dimensional Space-Time continuum, and all events, places, moments in history, are referred to in terms of their location in Space-Time.

How the waves are found now with collision of black holes?

The phenomenon that the LIGO experiment detected was the collision of two black holes, colliding a billion light years away.

Using the world's most sophisticated detector built connecting two observatories in Louisiana and Washington, the scientists listened for 20 thousandths of a second as the two giant black holes, one 35 times the mass of the sun, the other slightly smaller, circled around each other and finally collapsed releasing energy.

Last year in September, the space disturbance that was generated after the black holes collided was picked up by some of the world's most sophisticated machines, as mentioned in media reports. These were the LIGO detectors used earlier.[Read here]

However, strong signals were captured when the new advanced LIGO detectors were brought into operation for their first observing run.

Future course of action:

The gravitational-wave observations have opened up a fundamentally new astronomical window to the Universe in the near future.

Astronomers had not only their eyes but also ears on the space for listening to the echo of the celestial merger of the two black holes, colliding a billion light-years away in the past.

A similar facility is being planned in India in a direction opposite to the two American observatories in Louisiana and Washington.

"We need detectors in many more directions so that the exact route of the gravitational wave can be traced... hence, the proposal to set up an observatory in India," said Somak Raychaudhury Raychaudhury, Director of Pune's Inter-University Centre for Astronomy and Astrophysics (IUCAA). [Read here]

This revelation will help in tracking Supernovas, which are explosion of a giant star, ahead of time. It will also help to track major celestial phenomenon as well as the noise created by gravitational bodies travelling in space.

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