Interferometer | animation

Most precise ruler ever built This animation illustrates how the twin observatories of LIGO work. One observatory is in Hanford, Washington, the other in Livingston, Louisiana. Each houses a large-scale interferometer, a device that uses the interference of two beams of laser light to make the most precise distance measurements in the world. The animation begins with a simplified depiction of the LIGO instrument. A laser beam of light is generated and directed toward a beam splitter, which splits it into two separate and equal beams. The light beams then travel perpendicularly to a distant mirror, with each arm of the device being 4 kilometers in length. The mirrors reflect the light back to the beam splitter, repeating this process 200 times. When gravitational waves pass through this device, they cause the length of the two arms to alternately stretch and squeeze by infinitesimal amounts, tremendously exaggerated here for visibility. This movement causes the light beam that hits the detector to flicker.