After more than a decade of planning, India this week approved building a gargantuan detector to sense ripples in space and time called gravitational waves, extending an international network of such devices. Expected to be operational by the decade's end, the new detector, near Aundha in western India, will be nearly identical to those in the Laser Interferometric Gravitational-Wave Observatory (LIGO) in Louisiana and Washington state. Each of those detectors is an L-shaped optical device called an interferometer with arms 4 kilometers long that make ultraprecise measurements of space in perpendicular directions. LIGO-India will use a spare set of LIGO mirrors and lasers. India will spend $320 million to construct the vacuum chamber and buildings to house the device. Since 2015, LIGO and Italy's Virgo detector have detected the fleeting signals of gravitational waves from 90 high-energy celestial events in which two massive objects such as black holes collided. Adding another detector should enable scientists to more precisely pinpoint sources in the sky.
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