Saturday, 13 February 2016

Gravitational waves detected 100 years after Einstein's prediction

Waves in black holes detected in scientific milestone
Existence of gravitational ripples was first proposed by Einstein a century ago
The Straits Times, 12 Feb 2016

CAMBRIDGE (Massachusetts) • Scientists said yesterday that they have for the first time detected gravitational waves, ripples in space and time hypothesised 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, spiralled inwards 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.

Detection of gravitational waves
Gravitational waves have been detected for the first time ever. Einstein thought they would exists as part of his general theory of relativity - but what are they and why are scientists so excited about all this? Find out more:
Posted by Reuters on Thursday, February 11, 2016

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 by scientists from the California Institute of Technology, the Massachusetts Institute of Technology (MIT) 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 4km-long 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 on Sept 14 last year.

“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 US government.

A landmark day for Einstein and our understanding of the universe: the detection of gravitational waves. World Science Festival's own Brian Greene explains the discovery.
Posted by Albert Einstein on Thursday, February 11, 2016

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.

Scientists said gravitational waves open a door for a new way to observe the universe and gain knowledge about enigmatic objects like black holes and neutron stars. By studying gravitational waves, they also hope to gain insight into the nature of the very early universe, which has remained mysterious.

Scientists sounded positively giddy over the latest discovery.

“It is really a truly, truly exciting event,” said theoretical physicist Abhay Ashtekar, director of Penn State University’s Institute for Gravitation and the Cosmos. “It opens a brand-new window on the universe.”

“The LIGO announcement describes one of the greatest scientific discoveries of the past 50 years,” Cornell University physicist Saul Teukolsky added.


One fleeting chirp, one epic discovery
Detection of gravitational waves, a key part of general theory of relativity, is a game-changer
The Straits Times, 13 Feb 2016

PARIS • When Albert Einstein forged the bedrock theory of modern physics 100 years ago, he had no computer, no Internet, no printer - ballpoint pens and pocket calculators did not exist and few homes had telephones.

Yet, it took one of the most sophisticated scientific tools ever built, at a cost of hundreds of millions of dollars, to prove an idea the scientist had crafted with little more than paper, a fountain pen, hard work and a mind sharper than most.

On Thursday, physicists announced they had detected gravitational waves - hitherto a key unproven element of Einstein's general theory of relativity.

The thesis was published 100 years ago this year, when the world was a very different place, inhabited by a man way ahead of his time.

Radios had been invented, but not yet entered people's homes. The Eiffel Tower was the tallest building in the world.

The team of physicists told the world they had heard and recorded the sound of two black holes colliding one billion light-years away, little more than a fleeting chirp.

But that faint rising tone, physicists said, is the first direct evidence of gravitational waves, the ripples in the fabric of space-time that Einstein predicted.

It completes his vision of a universe in which space and time are interwoven and dynamic, able to stretch, shrink and jiggle.

And it is a ringing confirmation of the nature of black holes, the bottomless gravitational pits from which not even light can escape, which were the most foreboding part of his theory.

"We are really witnessing the opening of a new tool for doing astronomy," Massachusetts Institute of Technology (MIT) astrophysicist Nergis Mavalvala said.

"We have turned on a new sense. We have been able to see and now we will be able to hear as well."

Conveyed by these gravitational waves, power 50 times greater than the output of all the stars in the universe combined vibrated a pair of L-shaped antennas in Washington state and Louisiana known as a Laser Interferometer Gravitational-wave Observatory, or LIGO, on Sept 14 last year.

If replicated by future experiments, that simple chirp seems destined to take its place among the great sound bites of science, ranking with Alexander Graham Bell's "Mr Watson - come here" and Sputnik's first beeps from orbit.

Experts said the first direct detection of gravitational waves is likely to earn a Nobel Prize.

Detectable gravitational waves open exciting new avenues in astronomy - allowing measurements of faraway stars, galaxies and black holes based on the waves they make.

Scientists said gravitational waves should help them gain knowledge about enigmatic objects like black holes and neutron stars.

The waves also may provide insight into the mysterious nature of the very early universe.

The scientists said that because gravitational waves are so radically different from electromagnetic waves, they expect them to reveal big surprises about the universe.

Everything we knew until now about the cosmos stemmed from electromagnetic waves such as radio waves, visible light, infrared light, X-rays and gamma rays.

Because such waves encounter interference as they travel across the universe, they can tell only part of the story.

Gravitational waves experience no such barriers, meaning they offer a wealth of additional information. Black holes, for example, do not emit light or radio waves but can be studied through gravitational waves.

When Einstein announced his theory, he rewrote the rules regarding space and time that had prevailed for more than 200 years, since the time of Newton, which stipulated a static and fixed framework for the universe.

Instead, Einstein said, matter and energy distort the geometry of the universe in the way a heavy sleeper causes a mattress to sag, producing the effect we call gravity.

A century on, scientists finally have the equipment sensitive enough to detect the waves.

LIGO's antennas are L-shaped, with perpendicular arms 4km long.

The lasers can detect changes in the length of one of those arms as small as 0.0001 (one ten-thousandth) the diameter of a proton - a subatomic particle too small to be seen by even the most powerful microscopes - as a gravitational wave sweeps through.

The discovery is a vindication for the US National Science Foundation, which spent about US$1.1 billion (S$1.5 billion) over more than 40 years, facing down criticism that sources of gravitational waves were not plentiful or loud enough to justify the cost. Now one of the key parts of Einstein's work has been proven and it could change astronomy and how we view the universe forever.


Einstein's Theories Explained
Einstein predicted Thursday's discovery of gravitational waves a century ago - here's what else he got right:
Posted by Sky News on Thursday, February 11, 2016

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