LIGO

The two LIGO (Laser Interferometer Gravitational-wave Observatory) interferometers are similar in principle to the Michelson interferometers used for many laboratory measurements. They have been joined by the VIRGO interferometer in Italy.

Basic design of the LIGO interferometers. Credit: LIGO/Shane Larson LIGO干涉仪的基本设计。资料来源：LIGO/Shane Larson

The description on the Caltech site is: "At each observatory, the two-and-a-half-mile (4-km) long L-shaped LIGO interferometer uses laser light split into two beams that travel back and forth down the arms (four-foot diameter tubes kept under a near-perfect vacuum). The beams are used to monitor the distance between mirrors precisely positioned at the ends of the arms. According to Einstein's theory, the distance between the mirrors will change by an infinitesimal amount when a gravitational wave passes by the detector. A change in the lengths of the arms smaller than one-ten-thousandth the diameter of a proton (10^-19 meter) can be detected."

References:
LIGO, NSF discussion

Caltech news release, February 11, 2016

LIGO Educator's Guide

LIGO Interferometers

LIGO facility in Hanford, Washington. 华盛顿州汉福德的LIGO设施

LIGO facility in Livingston, Louisiana. 路易斯安那州利文斯顿的LIGO设施

Image Credit: Caltech/MIT/LIGO Lab

VIRGO Interferometer

Image Credit: Caltech/MIT/LIGO Lab

Image Credit: The Virgo collaboration

The Virgo gravitational wave interferometer joins the two LIGO interferometers designed to detect gravitational waves from space. Virgo引力波干涉仪与两个设计用于探测来自空间的引力波的LIGO干涉仪联合工作。

References:

Virgo site