The LIGO and GEO 600 detectors

LIGO and GEO 600 are tools designed to measure changes in spacetime called gravitational waves . Gravitational waves are difficult to detect because they are very weak by the time they get to the earth.

LIGO and GEO detect gravitational waves by measuring changes in the pattern formed when two laser beams meet. These patterns depend on the length traveled by each laser beam, which changes when a gravitational wave passes through.

The sensitivity of this type of detector, called a laser interferometer, is proportional to the distance the laser beams travel. Since they look for tiny signals, LIGO and GEO need to be very large.