The Laser Interferometer Gravity-wave Observatory or LIGO for short is a complex located near the Hansford nuclear reactor in Washington State. This is a project being run by the National Science Foundation and carries a price tag of around $372 million.

LIGO consists mostly of two concrete tubes that are each 2.5 miles in length. The tubes are laid in an L shape. Each tube has been constructed to accomodate the slight curvature of the Earth over the distance that they cover. Each tube is a vacuum that is has an internal pressure of one-trillionth of an atmosphere. The centerpiece of the system is the laser that is fired towards the tubes which is one of the most perfect beams of light in the world. The laser is split and sent down the tubes and is bounced back and forth inside the vaccuum about 100 times. Then the lasers are brought back together on a detector that can sense almost every single proton that hits it. When the gravity-waves pass it changes the pattern on the detector and thus the researchers can "fingerprint" the wave.

The detector is so sensitive that there is a 30 foot no-walk zone around the mirrors. The system can pick up the gravity created by a human body which would create bogus results. The system also has to compensate for effects created by the moons gravity and other phenomena that can interfere with the detectors measurements. The research lab is also kept within strict standards so as not to interfere with the operation of the system. The air is supposedly 100 times cleaner than any office building.

Information drawn from

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