What : To detect gravitational waves
When : February 12,2016
After four months of analysis, a consortium of scientists— including from India — confirmed Thursday that they had detected a signal from space from 1.3 billion years ago. The signal, which travelled as a gravitational wave was from the fusion of two black holes into a single one — the first time ever that such a phenomenon was observed — and registered as a “çhirp’’ at two highly sensitive detectors, called the Laser Interferometer Gravitational Wave Observatory (LIGO) located in Washington and Louisiana.
Scientists say that this detection is as momentous as Galileo, 400 years ago. first using the telescope and getting a glimpse of what several celestial objects looked like magnified. “This is the first time that the universe has spoken to us in the language of gravitational waves,” said David Reitze, Executive Director of the LIGO Project. The discovery is proof that researchers, through gravitational waves, can now observe a new class of astronomical phenomena just as observing x-ray signals from space brought alive pulsar, neutron stars and a host of other unprecedented celestial objects.
Though the detectors were American, Indian scientists have contributed significantly in terms of designing algorithms that were used to analyse the signals registered by the detector and be sure that it was indeed from a gravitational wave. Indians have also made, three decades ago, theoretical contributions to understand how such black holes may collide into each other.
“It is an extremely significant find and Nobel worthy,”” said Bala Iyer, a theoretical physicist and among the leaders of the Indian consortium that contributed to the find. Immediately after the confirmation of the waves were formally announced, Prime Minister Narendra Modi tweeted his congratulations and announced approval for a project to have a gravitational-wave detector in India, a project that has been on the anvil for several years.
Gravitational waves are the last, unobserved prediction from Albert Einstein’s iconic general relativity equations that were developed 100 years ago. These equations are the reason space and time — in the eyes of contemporary science — are seen as malleable shape-shifting entities rather than fixed and eternal, as our senses suggest to us. Black holes, which result when stars die, can collide with each other and sometimes birth new universes. These collisions are so violent that they can distort space and time around it, just as dropping a heavy ball on a tarpaulin sheet can massively wrinkle it. These wrinkles propagate, as gravitational waves through space-time but are extremely hard to detect. The LIGO detectors built between 2002-2010 to spot these waves but to no avail.
Last year, both detectors got a $200 million upgrade, so much so, that they were renamed advance-LIGO. Research and analysis of data from the detectors is carried out by a global group of scientists, including the LIGO Scientific Collaboration (LSC), which includes several Indian scientists.
The detectors are made to be extremely sensitive to the slightest of vibrations and that makes it a technical challenge to be sure that these detectors have caught a gravitational wave and not a, say the rumble of a passing truck.
THe black holes that were detected were roughly 25 to 30 times the mass of the sun and squeezed into a diameter of 150 kms. Their collision was after they swirled into each other at half the speed of light releasing the gargantuan shockwaves.
- What are gravitational waves?Gravitational waves are small ripples in space-time that are believed to travel across the universe at the speed of light. They are like tiny waves on a lake — from far away, the lake’s surface looks glassy smooth; only up very close can the details of the surface be seen. They were predicted to exist by Albert Einstein in 1916 as a consequence of his General Theory of Relativity.
- What does Einstein say about gravity?While Sir Isaac Newton visualised gravitational force as a pulling force between objects, Albert Einstein opined it to be a pushing force due to the curvature of four dimensional spacetime fabric. The curvature of spacetime stems from the dent heavy objects produce on spacetime fabric, which can be compared to the dent one could see on a plastic sheet when a massive ball is placed.
- How are these waves detected?Scientists have been trying to detect them using two large laser instruments in the United States, known together as the Laser Interferometer Gravitational-Wave Observatory (LIGO), as well as another in Italy.The twin LIGO installations are located roughly 3,000 km apart in Livingston, Louisiana, and Hanford, Washington. Having two detectors is a way to sift out terrestrial rumblings, such as traffic and earthquakes, from the faint ripples of space itself.The LIGO work is funded by the National Science Foundation, an independent agency of the U.S. government.
- Why is the study of gravitational waves important?Discovery of gravitational waves would represent a scientific landmark, opening the door to an entirely new way to observe the cosmos and unlock secrets about the early universe and mysterious objects like black holes and neutron stars.
- Did scientists ever detect gravitational waves?Although, physics supports the existence of gravitational waves, the strength of such waves even due to astronomically heavy bodies is awfully weak to be detected.On March 17, 2014, Harvard-Smithsonian Centre for Astrophysics erroneously claimed discovery of gravitational waves. The Harvard group, working at BICEP2 (Background Imaging of Cosmic Extragalactic Polarisation) telescope, had reported that they had observed a twist in the polarisation of ancient light that goes back to the time of the big bang. But within a month, studies pointed out flaws in the study.