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Discovery confirms Einstein's theory, opens new branch of study

Posted February 11

LIGO detects gravitational waves from merging black holes (Credit:  LIGO, NSF, Aurore Simonet)

A new type of astronomy based on a century-old prediction by Albert Einstein was confirmed by a team of astrophysicists at the Laser Interferometer Gravitational-Wave Observatory (LIGO) last year and announced Thursday.

Einstein theorized that the fabric of space-time is curved by anything massive, like a sun or planet. Like a rock dropped into a pond, when cataclysmal events happen, such as stars exploding or black holes merging (as was observed in September), those curves ripple out elsewhere as gravitational waves. Like those ripples in the pond, the further out you are from that event, the smaller the ripples.

Scientists have been looking from those ripples using a pair of highly sensitive observatories in Livingston, La., and Hanford, Wash. Each bounces a laser back and forth through a pair of 2.5 mile-long airless tubes arranged at right angles to each other measuring the amount of time the light takes to travel. When those beams come back together they should align perfectly thanks to the unchanging speed of light.

Advanced LIGO detector

On Sept. 14, 2015, beams in Louisiana didn't line up indicating a blip in the space-time continuum. Seven milliseconds later, a nearly identical blip was observed 1,800 miles northwest in Hanford allowing the team to identify the source of the disturbance over 1 billion light years away.

LIGO spokesperson Gabriela González excitedly explained that "multicellular life here on Earth was just beginning to spread” when this event first occurred. Both observations nearly perfectly match Einstein's prediction of what gravitational waves from merging black holes should look like.

The discovery opens a new branch of astronomy: gravitational wave astronomy. This is significant because astronomy has been done to this point in the various bands of the electromagnetic spectrum such as radio waves, X-rays and, of course, visible light. Unlike energy in the electromagnetic spectrum which can be distorted by its environment, the universe is essentially transparent to gravitational waves. They pass through all matter.

Previously obscured astrophysical objects can now be observed. Additional LIGO observatories in India and Japan are planned to increase the ability to observe the Universe and answer fundamental questions about how black holes form, how matter acts in extreme environments around supernovae and neutron stars and whether Einstein’s general theory of relativity correctly describes gravity.


Tony Rice is a volunteer in the NASA/JPL Solar System Ambassador program and software engineer at Cisco Systems. You can follow him on twitter @rtphokie.

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