Explained Gravitational Waves Scientist Detect Record Gravitational Waves

Explained Gravitational Waves Scientist Detect Record Gravitational Waves
Scientist have confirmed that they've proven the existence of gravitational waves, proving Albert Einstein's Theory of Relativity

“We have detected gravitational waves. We did it,” said David Reitze, executive director of the Laser Interferometer Gravitational-Wave Observatory (Ligo), at a press conference in Washington.

The gravitational waves were detected on September 14, 2015 at 5:51 a.m. Eastern Daylight Time (09:51 UTC) by both of the twin Laser Interferometer Gravitational-wave Observatory (LIGO) detectors, located in Livingston, Louisiana, and Hanford, Washington, USA.

Based on the observed signals, LIGO scientists estimate that the black holes for this event were about 29 and 36 times the mass of the sun, and the event took place 1.3 billion years ago. About 3 times the mass of the sun was converted into gravitational waves in a fraction of a second—with a peak power output about 50 times that of the whole visible universe. By looking at the time of arrival of the signals—the detector in Livingston recorded the event 7 milliseconds before the detector in Hanford—scientists can say that the source was located in the Southern Hemisphere.

The Ligo discovery signals a new era in astronomy

The new LIGO discovery is the first observation of gravitational waves themselves, made by measuring the tiny disturbances the waves make to space and time as they pass through the earth.

According to general relativity, a pair of black holes orbiting around each other lose energy through the emission of gravitational waves, causing them to gradually approach each other over billions of years, and then much more quickly in the final minutes. During the final fraction of a second, the two black holes collide into each other at nearly one-half the speed of light and form a single more massive black hole, converting a portion of the combined black holes’ mass to energy, according to Einstein’s formula E=mc2. This energy is emitted as a final strong burst of gravitational waves. It is these gravitational waves that LIGO has observed.

Year – 1915 -1916
Albert Einstein predicted the existence of gravitational waves as part of the theory of general relativity.
His General Theory of Relativity, formulated in 1915, describes gravity as a consequence of the way mass curves "space-time," the fabric of the universe.

Gravitational waves are ripples in space-time, caused by bodies moving through the universe. Einstein's theory stated that time and space are not two separate concepts, but are instead intertwined, and warp each other in strange ways. Einsten's says that, instead, every object warps the space-time around it to create a gravitational "pull".

Scientists in subsequent decades looked for such gravitational waves but they failed to find gravitational waves.
The University of Maryland physicist Joseph Weber built gravitational-wave detecting devices and claimed to have discovered such waves, but his claims were disputed and ultimately discredited.

Other physicist persuaded the National Science Foundation to fund the creation of LIGO, which has two facilities, one in Livingston, La., and the other in Hanford, Wash.

The devices -- there is one in Livingston, Louisiana, and one in Hanford, Washington -- have been operating on and off for more than a decade.

The discovery was a collaboration between the California Institute of Technology, the Massachusetts Institute of Technology and LIGO, which is a pair of kilometers-long laser devices designed to detect gravitational waves.


Year – 2015 – 2016

Now Scientist have confirmed that they've proven the existence of gravitational waves, proving Albert Einstein's Theory of Relativity

LIGO, a system of two identical detectors carefully constructed to detect incredibly tiny vibrations from passing gravitational waves, was conceived and built by MIT and Caltech researchers, funded by the National Science Foundation, with significant contributions from other U.S. and international partners. The twin detectors are located in Livingston, Louisiana, and Hanford, Washington. Research and analysis of data from the detectors is carried out by a global group of scientists, including the LSC, which includes the GEO600 Collaboration, and the VIRGO Collaboration.

Dr. David Reitze, executive director of the Laser Interferometer Gravitational-Wave Observatory (LIGO), said that the detected waves were found on Sept. 14 and were produced during the merger of two black holes that became a single, more massive black hole.

The researchers at the National Science Foundation, MIT, and Caltech have been collaborating on the project using their two Laser Interferometer Gravitational-Wave Observatories (LIGO) to measure atomic-level differences in gravitational interference.

The group says that, on September 14, 2015, the LIGO recorded and measured weak gravitational waves emanating from the merging of two distant supermassive black holes some 1.3 billion years ago.

What is a gravitational  wave?
Rippling out from a super- massive collision, for example between two black holes, gravity waves could be detected through the stretching and contracting of space and time


Gravitational waves carry information about their dramatic origins and about the nature of gravity that cannot otherwise be obtained. Physicists have concluded that the detected gravitational waves were produced during the final fraction of a second of the merger of two black holes to produce a single, more massive spinning black hole. This collision of two black holes had been predicted but never observed.


How LIGO works?
LIGO – Laser Interferometer gravitational wave observatories
LIGO is an interferometer. It works by splitting a laser beam in two, sending the halves to and fro along paths identical in length but set at right angles to one another, and then looking for interference patterns when the halves are recombined. If the half-beams’ paths are undisturbed, the waves will arrive at the detector in lock-step. But a passing gravitational wave will alternately stretch and compress the half-beams’ paths. Those half-beams, now out of step, will then interfere with each other at the detector in a way that tells of their experience. The shape of the resulting interference pattern contains all manner of information about the wave’s source, including what masses were involved and how far away it was.

in order to achieve the required sensitivity, each arm of each interferometer is 4km long and the half-beam in it is bounced 100 times between the mirrors at either end of the arm, to amplify any discrepancy when the half-beams are recombined.

Two special facilities in the USA located at Louisiana and other in the Washington state listen for gravitational energy that can indicate when and where cataclysmic events occurred in space.

LIGO has been measuring gravitational waves from much denser bodies; black holes.

How LIGO identifies distortion of space and detect gravitational wave?

1 -
A single laser beam is split and directed down two identical tubes

2-
Mirrors reflect the twin beams back to a detector

3-
Back inside the detector, the laser beams arrive perfectly aligned

4-
Recombined, they cancel each other out
No light is detected.

5-
When space-time is distorted by a gravity wave, the two tubes change length. One tube stretches as the other contracts over and over until the wave has passed
As the distances fluctuate the peaks and troughs of the two returning laser beams move in and out of alignment The recombined waves no longer cancel each other out. Light reaches the detector and the gravity wave can be measured
Light is detected.

LIGO and India -
For gravitational astronomy, this is just the beginning. Soon, LIGO will not be alone. By the end of the year VIRGO, a gravitational-wave observatory in Italy, should join it in its search. Another is under construction in Japan and talks are under way to create a fourth, in India.

LIGO Laboratory is working closely with scientists in India at the Inter-University Centre for Astronomy and Astrophysics, the Raja Ramanna Centre for Advanced Technology, and the Institute for Plasma to establish a third Advanced LIGO detector on the Indian subcontinent. Awaiting approval by the government of India, it could be operational early in the next decade. The additional detector will greatly improve the ability of the global detector network to localize gravitational-wave sources.

1980 – 2016
India - Pune
Gravitational waves and Sanjeev Dhurandhar
Pune-born Dhurandhar is one of the 1,000 key scientists involved in detecting gravitational waves.
Prof Jayant Narlikar, former IUCAA director told to media in 1980s when everyone was talking about electromagnetic waves and young scientist Sanjeev Dhurandhar was talking about theories and experiments related to gravitational waves.
Dhurandhar was told by senior colleagues that he had no credibility
Dhurandhar never gave up and in the process trained several students and focused his research in this area. Today most of Dhurandhar’s students are with gravitational wave groups in various countries and have been involved in this exciting discovery
Dhurandhar led the solo Indian group in the initial era of the Laser Interferometer Gravitational-Wave Observatory (LIGO) for a decade.

The Indian Initiative in Gravitational-Wave Observations (IndIGO), set up in 2009, involves 61 scientists from nine institutions — CMI Chennai, ICTS-TIFR Bengaluru, IISER-Kolkata, IISER-Trivandrum, IIT Gandhinagar, IPR Gandhinagar, IUCAA Pune, RRCAT Indore and TIFR Mumbai. The discovery paper has 35 authors from these institutions.

Watch the video How LIGO works?
LIGO Gravitational Wave Observatory



Watch the video Journey of a Gravity Wave




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Friday, February 12, 2016

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