More details about LIGO’s discovery of gravitational waves

Although this shared email has little to do with ‘Gene-Environment Interactions’, this represents one of the coolest (Nobel Prize-worthy) experiments in Physics, which led to a finding/observation that proves Einsteins’s Theory of Relativity a century ago.

At 11:53 am local time on 14 Sept 2o15, an automated email appeared in the inbox of Marco Drago, physicist at the Max Planck Institute for Gravitational Physics in Hannover, Germany. The email contained links to two plots, each showing a wave that had emerged suddenly from a noisy background and ended in a crash. This was the signal that Drago had been trained to spot, and that the US-led Advanced Laser Inter­ferometer Gravitational-Wave Observatory (LIGO) where he works …was built to detect: Signature Ripples in space-time produced when two black holes collide to form a single gravitational sink. No human has ever directly detected gravitational waves before, nor the merging of two black holes. The plots, one from each of LIGO’s twin detectors in Hanford, Washington, and Livingston, Louisiana, … would go on to make history.

Attempting to spot merging black holes has been LIGO’s ultimate goal. And, seeing them immediately “exceeds all expectations for something amazingly novel and new.  A black hole can form when a huge star burns out and collapses to a point––leaving behind a gravitational field so strong, near that point––that not even light can escape. That gravitational field is the Black Hole, and––thanks to Einstein’s equivalence of energy and mass, E = mc2––the black hole has a mass.

Astrophysicists have spotted stellar-mass black holes mostly in our galaxy by searching for systems in which a black hole consumes a companion star. From the motion of the star and the gas streaming into the black hole, researchers have deduced that the heaviest of them weighs about 15 times as much as our Sun. [Much heavier black holes, with masses of millions of suns, are located at the heart of our galaxy and many other galaxies.]

LIGO’s triumph is a fitting end to the tale that Einstein began (1905-15). He never believed that black holes existed. But, although astronomers had accumulated compelling evidence for black holes by observing their surroundings, notes Thibault Damou (theoretical physicist at Institute of Advanced Scientific Studies near Paris), the LIGO signal on 14 Sept 2o15 is “the first real direct proof of their existence”.

 Science  19 Feb 2o16;  351: 796–797

Nature  18 Feb 2o16;  530: 261–263 (actually the last page is a related article)

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