Friday, February 12, 2016

Gravitational Waves

Scientists have detected gravitational waves -- you know, ripples in space and time hypothesized by Albert Einstein a century ago -- in a landmark discovery that opens a new window for studying the cosmos.

Using a pair of giant laser detectors, researchers identified gravitational waves coming from two black holes, extraordinarily dense astronomical objects that orbited one another, spiraled inward and smashed together. The waves were the product of a collision between two black holes 30 times as massive as the Sun, located 1.3 billion light years from Earth.

The startling conclusion is that it is space itself that is rippling.

Einstein proposed the existence of gravitational waves in 1916 as an outgrowth of his ground-breaking general theory of relativity, which depicted gravity as a distortion of space and time triggered by the presence of matter. Until now, scientists had found only indirect evidence of the existence of gravity waves.

Heavy celestial objects bend space and time but because of the relative weakness of the gravitational force the effect is miniscule except from massive and dense bodies like black holes and neutron stars. When these objects collide, they send out ripples in the curvature of space and time that propagate as gravitational waves.

The discovery of gravitational waves already has already provided unique insight into black holes, with scientists saying it has demonstrated that there are plenty of black holes in the range of tens of solar masses, resolving the long debated issue of the existence of black holes of that size.

A black hole, a region of space so packed with matter that not even photons of light can escape the force of gravity, was detected for the first time in 1971. Scientists have known the existence of small black holes and so-called supermassive black holes are millions or billions of times as massive as the sun, but had debated the existence of black holes of intermediate size.

Neutron stars are small, about the size of a city, but are extremely heavy, the compact remains of a larger star that died in a supernova explosion.

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