Advancing Basic Science for Humanity
The Laser Interferometer Gravitational-Wave Observatory (LIGO)1 is an ambitious physics experiment designed to measure gravitational waves reaching our planet from deep space. Gravitational waves are elusive ripples in the fabric of the universe. First predicted to exist a century ago, they have never been directly detected. LIGO is designed to register the astonishingly tiny effects of passing gravitational waves here on Earth using a precise arrangement of mirrors and lasers, monitoring equipment and other advanced technologies.
LIGO's mission is to detect gravitational waves directly, use them to explore the fundamental physics of gravity and develop gravitational wave astronomy as a tool for science. The project was co-founded in 1992 by Kip Thorne and Ronald Drever of the California Institute of Technology (Caltech) and Rainer Weiss of the Massachusetts Institute of Technology (MIT). LIGO has grown into an international collaboration of more than 900 scientists at over 80 institutions, organized by the LIGO Scientific Collaboration (LSC). (Click here to see a list of all participating institutions.) Caltech and MIT operate LIGO on behalf of the LSC.
LIGO consists of two detectors situated 1,865 miles (3,002 kilometers) apart in isolated regions in the states of Washington and Louisiana. Each facility features two arms positioned at right angles to each other and running 2.5 miles (4 kilometers) from a central building. Lasers are beamed down each arm and bounced back by mirrors, essentially acting as a ruler for the arm. Sensitive detectors can tell if the length of the arms of a LIGO detector varies ever so slightly as a result of passing gravitational waves—on the scale of 1/10,000 of the diameter of a proton.
LIGO first began searching for gravitational waves in August 2002. Its initial observing run went through the end of 2010 without a detection. This was followed by a planned, several-year shutdown to upgrade components for an Advanced LIGO (aLIGO) mission that began in September 2015. The upgrade boosted LIGO's sensitivity to gravitational waves by about 10 times, extending its detection range as far as 225 million light-years away. Learn more about how LIGO works and the aLIGO upgrade here.
Einstein's Messengers is an award-winning documentary on LIGO, NSF's Laser Interferometer Gravitational Wave Observatory. (Credit: National Science Foundation)