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Physicists Gear Up To Catch a Gravitational Wave
sciencehabit writes: A patch of woodland just north of Livingston, Louisiana, population 1893, isn't the first place you'd go looking for a breakthrough in physics. Yet it is here that physicists may fulfill perhaps the most spectacular prediction of Albert Einstein's theory of gravity, or general relativity. Structures here house the Laser Interferometer Gravitational-Wave Observatory (LIGO), an ultrasensitive instrument that may soon detect ripples in space and time set off when neutron stars or black holes merge. Einstein himself predicted the existence of such gravitational waves nearly a century ago. But only now is the quest to detect them coming to a culmination. Physicists are finishing a $205 million rebuild of the detectors, known as Advanced LIGO, which should make them 10 times more sensitive and, they say, virtually ensure a detection.
There *is* a second detector (a third even!) The second main detector is in eastern Washington state. Both will have to go ping before you accept any result.
Little do they know, they ARE doing the experiment in a simulation.
...but it's being eaten...by some...Linux or something...
There are two more detectors at the Hanford Washington site. A primary one like at Livingston, and a secondary one that's half the length.
Also, there is an European experiment in Italy, called Virgo. It's currently being upgraded to similar sensitivity to the other 3.
When they are all working, it will allow the detection to not only be verified, but the time of the events at each detector will let them triangulate the location the wave originated from.
We're pretty darn sure of gravitational waves, as a Nobel prize was awarded in 1993 for showing that the slowing of a binary pulsar was just the right amount to account for the gravitational waves it would generate.
These detectors will let us do gravitational wave astronomy much like we do with light and radio waves now.
The huge news would be if they get all of them working with their maximum sensitivity and didn't detect anything. That would mean something was very wrong with their assumptions.
LIGO works by measuring the distance between two tracks set at right angles. A passing gravitational wave would momentarily change the length of one leg or the other, or both, in characteristic ways.
It measures the distance with a laser beam. It splits the beam, and sends them down the two tracks. They bounce off mirrors, and when they return, they interfere. Changes in the length will change the interference. That means that they can detect changes at distances on the order of a single wavelength of light.
That's an interferometer, the I in LIGO. At its core, it's the same thing that Michaelson and Morley used to look for aether, and failed to find it. The trick is that this has to be even more sensitive, because the expected changes are even smaller and the contraption itself is much bigger (4 km, versus a few meters). They have to exclude all kinds of potential interference, from passing trucks to earthquakes.
I suppose it may well go "ping" when it spots a gravitational wave, and they'll end up comparing it to other experiments. But they'll get more than a ping; they'll get a signal of the changing lengths that they can use to map the size of the wave, and even a hint of its direction.
That being said I fully expect gravitational waves to be discovered.
I am not so sure. There have been other experiments that should have detected them, but didn't. If this experiment also comes up empty, then physics may be facing another Michelson–Morley moment.