Tag: Gravitational waves

Gravitational waves and the road to a Nobel prize

The question on the lips of participants of the Lindau Nobel Laureate Meeting was not if the detectors of gravitational waves would win a nobel prize for their work. It was a matter of when. The Nobel prize for physics will be announced within the next 100 days.

On 11 February this year, scientists from the LIGO collaboration announced that they have detected gravitational waves. This was followed up by a second detection last month. The waves were caused by giant black holes merging in events that took place more than a billion years ago.

Gravitational waves are distortions in space and time that, rather than the force of gravity, explain the movement of planets, stars and galaxies. In his 1916 theory of General Relativity, Albert Einstein predicted the existence of these waves, linking space and time.

“It’s been 100 years [since Einstein predicted gravitational waves],” said Nobel prize winner George Smoot. “It was a long argument that went on for a long time: for the theory, it was 40 years of arguing [whether they exist], and then the experiments involved 60 years of arguing.”

Their detection “opens up a whole new era … a new branch of astronomy”, Smoot said on the sidelines of the Lindau meeting, which was dedicated to physics.

LIGO, which stands for Laser Interferometer Gravitational-wave Observatory, is a system of two detectors, one in Louisiana and the other in Washington.

Each detector involves two 4km tunnels that meet at right angles (like an L). A laser beam is split to run down the two tunnels, and is then reflected back and forth downt he tunnels. There is a detector where the two arms meet. If there are no gravitational waves, the laser beams cancel each other out at the detector, because the laser beams have both travelled the same distance. But if there is a ripple in space time, the distance travelled by the beams differs slightly, and this is picked up by the detector.

Think of two people on opposite sides of the equator who start walking towards the North Pole: they will meet eventually, not because there is a force pulling them together, but because the Earth is curved. The same idea applies to the rest of the universe: planets, stars and galaxies moves in certain ways because space itself is curved.

Although LIGO has been around since 2002, it only detected these gravitational waves after a multi-million dollar overhaul.

Smoot, who received his Nobel prize for the detection of the cosmic microwave radiation background, said that the next 20 years would involve improving detectors and observatories and creating new ones for “gravity wave astronomy”.

“Up to now, we’ve been deaf to gravitational waves, but now we can hear them,” David Reitze, LIGO executive director at the California Institute of Technology (Caltech), said at the announcement of the first detection in February. “We’ll hear things we expected to hear … But also things we never expected.”

Wild was a recipient of the Academy of Science of South Africa’s Lindau Nobel Laureate Meeting fellowship

This article first appeared in the Sunday Independent on 3 July 2016.

State of the Cosmos: gravitational waves

This was perhaps the worst-kept secret in all of science: the detection of gravitational waves.

It has been seeping out of sources like leaky taps. But on 11 February, it was finally announced that scientists had detected gravitational waves.

Gravitational waves are distortions in space and time that – rather than the force of “gravity” – explain the dances of planets, stars and galaxies.

In 1916, in his theory of General Relativity Albert Einstein predicted the existence of these gravitational waves, linking space and time. Now, a century later, scientists from the California Institute of Technology, the Massachusetts Institute of Technology and the LIGO scientific collaboration called the media together to tell them what they have been anticipating for weeks.

LIGO, which stands for Laser Interferometer Gravitational-wave Observatory, is a system of two detectors, one in Louisiana and the other in Washington.

LIGO
LIGO

Each detector involves two 4km tunnels that meet at right-angles (like an L). A laser beam is split to run down the two tunnels, and is then reflected back and forth down the tunnel. There is a detector at the juncture of the two arms.

If there are no gravitational waves, the laser beams cancel each other out at the detector (because the laser beams have both travelled the same distance). But if there is a ripple in space time, the distance travelled by the beams differs slightly, and this is picked up at the detector.

Think of two people at opposite sides of the equator who start walking towards the North Pole: they will meet eventually, not because there is a force pulling them together, but because the planet is curved. The same idea applies into the rest of the universe, explaining the motion of planets and stars.

Although the dedicated gravitational-wave-hunting facility has been around since 2002, by 2010 it hadn’t detected the merest ripple. It got a five-year overhaul, and opened for business again in September 2015. Within six months, this $620-million facility has brought something to the table.

To be fair, though, gravity is a very weak force (comparatively) and gravitational waves are very difficult to detect (which is an example of stating the obvious because despite billions of dollars in experiments around the world, this is the first time they have been detected).

The scientists on Thursday announced that they had detected the “ringing” of two black holes colliding about 1.3-billion light years away.

Unlike other claims that were later disproved, this group came prepared with a peer-reviewed paper, published in Physical Review Letters.

“Up to now, we’ve been deaf to gravitational waves, but now we can hear them,” David Reitze, LIGO executive director at Caltech, said. “We’ll hear things we expected to hear … But also things we never expected.”