 "Ligo 'chirp' confirms Einstein's gravity waves")
The Laser Interferometer Gravitational-Wave Observatory (Ligo), Caltech, announced on Thursday that it had detected gravitational waves, confirming a major prediction of Albert Einstein's Theory of General Relativity.
In his "field equations", also known as Einstein's Equations and first published in 1915, Einstein hypothesised that gravity worked as waves, causing distortions and warps in space-time.
Gravity waves pass through all matter. The effect is to cause changes in the dimensions of objects, which will be stretched in one direction and compressed in another by a given wave. However, the effects are very small and very hard to detect.
The idea of Ligo - a laser system sensitive enough to detect such waves - occurred over 50 years ago. But the technology to detect such small variations in space-time (and to rule out interference) was developed very recently.
A noise heard at the Ligo labs, described by astronomers as a "chirp", confirmed the discovery.
There are two Ligo labs in the US - in Livingston, Louisiana and Hanford, Washington - where scientists from 16 countries, including some from India, are involved in interpretation data and results. Both Ligo facilities are constructed around two four-km-long tunnels, set in an L-shape, with each tunnel perpendicular to the other. Perpendicular waves do not affect each other.
A laser beam is split and pushed through the tunnels and bounced back and measured. "Interferometers" (instruments that can decompose or superimpose waves) are set at the intersection of the tunnels. If there's a perturbation caused by gravity waves, the dimensions of the tunnels vary slightly. The interferometers pick up those tiny changes.
Think of this as a very fine-tuned "smart" mirror, which will not reflect light if the tunnels stay exactly at their normal dimensions. But if the dimensions vary, light is reflected. In effect, that is what the apparatus does. On September 14, 2015, both the Ligo labs picked up the same signal, within milliseconds of each other. It could actually be heard as a noise, astronomers described it as a "chirp" and the signal was played out, slowed down for the audience. The dimensions of the tunnels had varied for 21 milliseconds by a distance that was unimaginably small (10 to the power of -21 metres) but nevertheless detectable.
The effect was caused by the merger of two black holes at a distance of 1.3 billion light years (a light year is the distance travelled by light in 365 days at 300,000 km per sec). That merger of black holes had released a huge amount of energy calculated at the same amount that would be released by annihilating the mass of three suns. The observations almost exactly fitted Einstein's calculations.
This is the first time the universe has been observed through a gravitational telescope as opposed to optical or electromagnetic ratio telescopes. It was also the first time a binary black hole has been found and studied.
The use of gravity to study the universe opens up an entirely new field. It could lead to many more fundamental breakthroughs. The next stage involves ramping up the Ligo sensitivity by 300 per cent and also the setting up of several new Ligo labs, including one in India.
This distortion in space-time is felt as gravity.
Einstein predicted gravity waves in 1915.
What was detected?
About 1.3 billion years ago, two black holes, each with mass 30 times our sun, collided, creating a new black hole, and a gravitational field. The field was so strong it distorted space-time in waves that rippled through space. Such events are thought to be common in our universe, but this was the first one ever detected.
By whom and how?
The search for gravity waves began in the 1960s, but it was only on Thursday that scientists at Laser Interferometer Gravitational-Wave Observatory (Ligo) announced that they had finally succeeded at detecting gravity waves. "We did it!" said Ligo Executive Director David Reitze.
The Ligo system is so sensitive that it can detect a change in the distance between the solar system and the nearest star (3.5 billion light years away) to the breadth of a human hair.
Compiled by Uttaran Das Gupta
In his "field equations", also known as Einstein's Equations and first published in 1915, Einstein hypothesised that gravity worked as waves, causing distortions and warps in space-time.
Gravity waves pass through all matter. The effect is to cause changes in the dimensions of objects, which will be stretched in one direction and compressed in another by a given wave. However, the effects are very small and very hard to detect.
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"We have detected gravitational waves. We did it," said David Reitze, executive director of Ligo, at a press conference in Washington.
The idea of Ligo - a laser system sensitive enough to detect such waves - occurred over 50 years ago. But the technology to detect such small variations in space-time (and to rule out interference) was developed very recently.
A noise heard at the Ligo labs, described by astronomers as a "chirp", confirmed the discovery.
There are two Ligo labs in the US - in Livingston, Louisiana and Hanford, Washington - where scientists from 16 countries, including some from India, are involved in interpretation data and results. Both Ligo facilities are constructed around two four-km-long tunnels, set in an L-shape, with each tunnel perpendicular to the other. Perpendicular waves do not affect each other.
A laser beam is split and pushed through the tunnels and bounced back and measured. "Interferometers" (instruments that can decompose or superimpose waves) are set at the intersection of the tunnels. If there's a perturbation caused by gravity waves, the dimensions of the tunnels vary slightly. The interferometers pick up those tiny changes.
Think of this as a very fine-tuned "smart" mirror, which will not reflect light if the tunnels stay exactly at their normal dimensions. But if the dimensions vary, light is reflected. In effect, that is what the apparatus does. On September 14, 2015, both the Ligo labs picked up the same signal, within milliseconds of each other. It could actually be heard as a noise, astronomers described it as a "chirp" and the signal was played out, slowed down for the audience. The dimensions of the tunnels had varied for 21 milliseconds by a distance that was unimaginably small (10 to the power of -21 metres) but nevertheless detectable.
The effect was caused by the merger of two black holes at a distance of 1.3 billion light years (a light year is the distance travelled by light in 365 days at 300,000 km per sec). That merger of black holes had released a huge amount of energy calculated at the same amount that would be released by annihilating the mass of three suns. The observations almost exactly fitted Einstein's calculations.
This is the first time the universe has been observed through a gravitational telescope as opposed to optical or electromagnetic ratio telescopes. It was also the first time a binary black hole has been found and studied.
The use of gravity to study the universe opens up an entirely new field. It could lead to many more fundamental breakthroughs. The next stage involves ramping up the Ligo sensitivity by 300 per cent and also the setting up of several new Ligo labs, including one in India.
| UNBELIEVABLY HUGE! |
| What is a gravity wave? A gravity wave ripples out of a super-massive collision, like one between two black holes. They can be detected, as the waves stretch and contract space and time. What Einstein told us about gravity Albert Einstein found out that space and time were interwoven into a single continuum called space-time, and massive objects cause distortion in this continuum. |
Einstein predicted gravity waves in 1915.
What was detected?
About 1.3 billion years ago, two black holes, each with mass 30 times our sun, collided, creating a new black hole, and a gravitational field. The field was so strong it distorted space-time in waves that rippled through space. Such events are thought to be common in our universe, but this was the first one ever detected.
By whom and how?
The search for gravity waves began in the 1960s, but it was only on Thursday that scientists at Laser Interferometer Gravitational-Wave Observatory (Ligo) announced that they had finally succeeded at detecting gravity waves. "We did it!" said Ligo Executive Director David Reitze.
The Ligo system is so sensitive that it can detect a change in the distance between the solar system and the nearest star (3.5 billion light years away) to the breadth of a human hair.
Compiled by Uttaran Das Gupta