Editing Michelson interferometer (section)

===Gravitational wave detection===
{{Main|Ground-based interferometric gravitational-wave search}}
Michelson interferometry is the leading method for the direct [[Gravitational-wave detector#Interferometers|detection of gravitational waves]]. This involves detecting tiny [[Strain (materials science)|strains]] in space itself, affecting two long arms of the interferometer unequally, due to a strong passing gravitational wave. In 2015 the first detection of [[gravitational waves]] was accomplished using the two Michelson interferometers, each with 4&nbsp;km arms, which comprise the [[LIGO|Laser Interferometer Gravitational-Wave Observatory]].<ref>{{cite web|url=https://www.ligo.caltech.edu/page/what-is-interferometer|title=What is an Interferometer?|website=LIGO Lab – Caltech|access-date=23 April 2018}}</ref> This was the first experimental validation of gravitational waves, predicted by [[Albert Einstein]]'s [[General Theory of Relativity]]. With the addition of the [[Virgo interferometer]] in Europe, it became possible to calculate the direction from which the gravitational waves originate, using the tiny arrival-time differences between the three detectors.<ref>{{cite web|url=https://www.ligo.caltech.edu/news/ligo20160211|title=Gravitational Waves Detected 100 Years After Einstein's Prediction|website=caltech.edu|access-date=23 April 2018}}</ref><ref name=nat>''Nature'', "Dawn of a new astronomy", M. Coleman Miller, Vol 531, issue 7592, page 40, 3 March 2016</ref><ref>''The New York Times'', "With Faint Chirp, Scientists Prove Einstein Correct", Dennis Overbye, February 12, 2016, page A1, New York</ref>  In 2020, [[India]] was constructing a fourth Michelson interferometer for gravitational wave detection.