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The working of LIGO :
LIGO , the largest and most ambitious project ever funded by NSF , consists of two massive L-shaped tubes called interferometers , one in Louisiana and the other in Washington State . Each arm of an L-tube is 4 km in length . Light beams are made to travel along the arms between pairs of mirrors . A passing gravitational wave would stretch space in one direction and shrink it in the perpendicular direction . This would increase the distance between one pair of mirrors and decrease the distance between the other pair . By swinging thus , the mirrors are responding to the stretching and compression of space-time . The minute changes in distance can then be registered by a detector , put in place to record the laser light returning from the two interferometer arms . To ensure that the signal received was an authentic gravitational wave , both interferometers need to do the " dancing mirrors " thing together causing the signal to be picked up by both detectors . When did LIGO detect waves ?
On 11 February 2016 , the LIGO collaboration announced the detection of gravitational waves , from a signal detected at 09:50:45 GMT on 14 September 2015 of two black holes with masses of 29 and 36 solar masses merging about 1.3 billion light years away . On 15 June 2016 , the LIGO group announced the detection of a second set of gravitational waves , which was observed at 03:38:53 GMT on 26 December 2015 .
The singularities about LIGO :
● Unlike optical or radio telescopes , LIGO cannot see electromagnetic radiation because gravitational waves are not part of the electromagnetic spectrum .
● As there is no need to collect light from stars or other objects in the Universe , LIGO doesn ' t need to be dish-shaped . LIGO has two long steel vacuum tubes arranged in the shape of an “ L ”.
● Gravitational wave observatories like LIGO cannot operate solo . The only way to definitively detect a gravitational wave is by operating in unison with a distant twin .
What other pioneering work is being done ? After decades of development and delays , the European Space Agency ( ESA ) has given the Laser Interferometer Space Antenna ( LISA ) mission there green signal . LISA will use three spacecraft to detect these minute ripples in the fabric of space-time . The spacecrafts will be stationed millions of kilometres apart in space , and linked via laser beams . Each spacecraft carries test masses that are shielded in such a way that the only force they respond to is gravity . Lasers measure the distances to test masses in all three spacecraft . Tiny changes in the lengths of each two-spacecraft arm signals the passage of gravitational waves through the formation .
Thus , gravitational waves are the very foundation of “ new astronomy ” - astronomy in which information about new cosmic events will be given not through light but through ripples in the fabric of spacetime itself . Only time can tell what new mysteries gravitational waves might solve .