February 11, 2016

Scientists find evidence of gravitational waves predicted by Einstein

Filed under: Big Bang, Black Holes, Cool, Cosmology, Gamma Ray Bursts — bferrari @ 11:54 am
File image - An image from a simulation showing how matter might be moved around in the extreme environment around a black hole. (Özel/Chan) (Özel/Chan)

File image – An image from a simulation showing how matter might be moved around in the extreme environment around a black hole. (Özel/Chan) (Özel/Chan)

After decades of searching, scientists announced Thursday that they have detected gravitational waves which are ripples in the fabric of space-time that were predicted by Einstein.


An international team of astrophysicist said that they detected the waves from the distant crash of two black holes, using a $1.1 billion instrument. The Ligo Collaboration was behind the discovery and it has been accepted for publication in the journal Physical Review Letters.

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“We have detected gravitational waves,” Caltech’s David H. Reitze, executive director of the LIGO Laboratory, told journalists at a news conference in Washington DC.

The news, according to the Associated Press, is being compared by at least one theorist to Galileo taking up a telescope and looking at the planets and the biggest discovery since the discovery of the Higgs particle. It has stunned the world of physics and astronomy, prompting scientists to say it the beginning of a new era in physics that could lead to scores more astrophysical discoveries and the exploration of the warped side of the universe.

“Our observation of gravitational waves accomplishes an ambitious goal set out over five decades ago to directly detect this elusive phenomenon and better understand the universe, and, fittingly, fulfills Einstein’s legacy on the 100th anniversary of his general theory of relativity,” Reitze said in a statement.

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The discovery confirms a major prediction of Albert Einstein’s 1915 general theory of relativity. Gravitation waves carry information about their dramatic origins and about the nature of gravity that cannot be obtained from elsewhere.

Not only have they fascinated by scientist by found their way into pop culture – namely through movies such as “Back To The Future,” where the space-time continuum was used a medium for the DeLorean time machine to go back in time. It also featured in the “Terminator” series.

Their existence was first demonstrated in the 1970s and 1980s by Joseph Taylor, Jr., and colleagues. In 1974, Taylor and Russell Hulse discovered a binary system composed of a pulsar in orbit around a neutron star. Taylor and Joel M. Weisberg in 1982 found that the orbit of the pulsar was slowly shrinking over time because of the release of energy in the form of gravitational waves. For discovering the pulsar and showing that it would make possible this particular gravitational wave measurement, Hulse and Taylor were awarded the 1993 Nobel Prize in Physics.

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In the latest breakthrough, the gravitational waves were detected on Sept. 14, 2015 by both of the twin Laser Interferometer Gravitational-wave Observatory (LIGO) detectors, located in Livingston, Louisiana, and Hanford, Washington.

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 three 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.

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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. In a final fraction of a second, the two black holes collide and form one massive black hole. A portion of their combined mass is converted to energy, according to Einstein’s formula E=mc2, and this energy is emitted as a final strong burst of gravitational waves.

These are the gravitational waves that LIGO observed.

“With this discovery, we humans are embarking on a marvelous new quest: the quest to explore the warped side of the universe — objects and phenomena that are made from warped spacetime. Colliding black holes and gravitational waves are our first beautiful examples,” Caltech’s Kip Thorne said.




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