In-Depth

Gravitational waves explained

A century ago, Albert Einstein hypothesised the existence of gravitational waves, small ripples in space-time that dash across the universe at the speed of light.

But scientists have been able to find only indirect evidence of their existence. On February 11, at a news conference called by the U.S. National Science Foundation, >researchers announced at long last direct observations of the elusive waves.

The discovery 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.

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.

Scientists spot elusive space-time ripples

The highly elusive ‘gravitational waves’ have finally been detected. Understandably, and justifiably, there is great elation within the global physics community, astrophysicists and cosmologists in particular. > Read more

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.

(“Piled Higher and Deeper” by Jorge Cham. www.phdcomics.com)

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.

What is LIGO?

The Laser Interferometer Gravitational-Wave Observatory is a large-scale physics experiment aiming to directly detect gravitational waves.

LIGO operates two gravitational wave observatories in unison: the LIGO Livingston Observatory in Livingston, Louisiana, and the LIGO Hanford Observatory, on the DOE Hanford Site, located near Richland, Washington. These sites are separated by 3,002 kilometers. Since gravitational waves are expected to travel at the speed of light, this distance corresponds to a difference in gravitational wave arrival times of up to ten milliseconds. Source:Wikipedia

Why is the study 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.

This article is closed for comments.
Please Email the Editor

Printable version | Jan 20, 2021 9:19:44 PM | https://www.thehindu.com/specials/in-depth/Gravitational-waves-explained/article15618312.ece

Next Story