IT'S OFFICIAL: Einstein was right

LIGO/Aurore Simonnet/Sonoma State University

Here’s what the first gravitational waves ever detected sound like

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WASHINGTON/CAMBRIDGE - Scientists said on Thursday they have for the first time detected gravitational waves, ripples in space and time hypothesized by physicist Albert Einstein a century ago, in a landmark discovery that opens a new window for studying the cosmos.

The researchers said they detected gravitational waves coming from two black holes - extraordinarily dense objects whose existence also was foreseen by Einstein - that orbited one another, spiraled inward and smashed together. They said the waves were the product of a collision between two black holes 30 times as massive as the Sun, located 1.3 billion light years from Earth.



The scientific milestone, announced at a news conference in Washington, was achieved using a pair of giant laser detectors in the United States, located in Louisiana and Washington state, capping a long quest to confirm the existence of these waves.

The announcement was made in Washington by scientists from the California Institute of Technology, the Massachusetts Institute of Technology and the LIGO Scientific Collaboration.
Like light, gravity travels in waves, but instead of radiation, it is space itself that is rippling. Detecting the gravitational waves required measuring 2.5-mile (4 km) laser beams to a precision 10,000 times smaller than a proton.




The two laser instruments, which work in unison, are known as the Laser Interferometer Gravitational-Wave Observatory (LIGO). They are able to detect remarkably small vibrations from passing gravitational waves. After detecting the gravitational wave signal, the scientists said they converted it into audio waves and were able to listen to the sounds of the two black holes merging.

"We're actually hearing them go thump in the night," MIT physicist Matthew Evans said. "We're getting a signal which arrives at Earth, and we can put it on a speaker, and we can hear these black holes go, 'Whoop.' There's a very visceral connection to this observation."
The scientists said they first detected the gravitational waves last Sept. 14.

"We are really witnessing the opening of a new tool for doing astronomy," MIT astrophysicist Nergis Mavalvala said in an interview. "We have turned on a new sense. We have been able to see and now we will be able to hear as well."
The LIGO work is funded by the National Science Foundation, an independent agency of the U.S. government.

Einstein in 1916 proposed the existence of gravitational waves as an outgrowth of his ground-breaking general theory of relativity, which depicted gravity as a distortion of space and time triggered by the presence of matter. But until now scientists had found only indirect evidence of their existence.

- source GMA News

Wobbling like jelly

According to the Massachusetts Institute of Technology's (MIT) David Shoemaker, the leader of the LIGO team, it looked just like physicists thought it would.

"The waveform that we can calculate based on Einstein's theory of 1916 matches exactly what we observed in 2015," David Shoemaker, the leader of the LIGO team, told Agence France-Presse.




"It looked like a chirp, it looked at something that started at low frequencies – for us low frequencies means 20 or 30 hertz, that's like the lowest note on a bass guitar, sweeping very rapidly up over just a fraction of a second... up to 150 hertz or so, sort of near middle C on a piano."

The chirp "corresponded to the orbit of these two black holes getting smaller and smaller, and the speed of the two objects going faster and faster until the two became a single object," he explained.

"And then right at the end of this waveform, we see the wobbling of the final black hole as if it were made of jelly as it settled into a static state."

- source Rappler Ph

Gravitational waves are so exciting because they were the last major prediction of Einstein's general theory of relativity that had to be confirmed, and discovering them will help us understand how the Universe is shaped by mass.

"Gravitational waves are akin to sound waves that travelled through space at the speed of light," said gravitational researcher David Blair, from the University of Western Australia. "Up to now humanity has been deaf to the universe. Suddenly we know how to listen. The Universe has spoken and we have understood."

What does that mean for us? Just think of all the breakthroughs that have come thanks to the discovery of x-rays and radio waves - now that we can detect gravitational waves, we're going to have a whole new way to see and study the Universe.

But let's step back for a second here and explain what gravitational waves actually are. According to Einstein's theory, the fabric of space-time can become curved by anything massive in the Universe. When cataclysmic events happen, such as black holes merging or stars exploding, these curves can ripple out elsewhere as gravitational waves, just like if someone had dropped a stone in a pond.

By the time those ripples get to us on Earth, they're tiny (around a billionth of the diameter of an atom), which is why scientists have struggled for so many years to find them.

But thanks to LIGO - the laser interferometer gravitational-wave observatory - we've finally been able to detect them. The LIGO laboratory works by bouncing lasers back and forth in two 4-km-long pipes, allowing physicists to measure incredibly small changes in spacetime.

One 14 September 2015, they picked up a relatively big change in their Livingston lab in Louisiana, what you'd call a blip in the system. Then, 7 milliseconds later, they detected the same blip with their lab in Hanford, Washington, 4,000 km away, suggesting that it had been caused by a gravitational wave passing through Earth.

In the months since, researchers have been rigorously studying this signal to see if it could have been caused by anything else. But the overwhelming conclusion is that the blip was caused by gravitational waves - the discovery has statistical significant of 5.1 sigma, which means there's only a 1 in 6 million chance that the result is a fluke.

In fact, the signal almost perfectly matches up with what scientists predicted gravitational waves would look like, based on Einstein's theory. You can see the signal below, with the predictions overlaid:

source sciencealert

-source science alert