The Twitter rumors are true! In what some scientists are calling the discovery of the century, LIGO (Laser Interferometer Gravitational-Wave Observatory) finally announced the first direct observation of gravitational waves.
Until a few days ago, gravitational waves were the only untested prediction of General Relativity. In General Relativity, space and time are not fixed. Spacetime curves around the matter and energy in the universe, ultimately creating a beautiful description of gravity. In one of the most mind boggling predictions, as two massive objects like black holes move relative to each other, ripples in space itself propagate outwards though the universe.
Of course, it is impossible to simply feel the effects of these ripples in spacetime. It took physicists 100 years to observe gravitational waves because their effects are so small. In order to detect waves created by two coalescing black holes, LIGO needed to make the smallest measurement in the history of mankind. Two 4 km long detectors were built 3000 km apart and operated in unison, sensitive to displacements in space 10,000 times smaller than a nucleus of an atom.
LIGO only needed one event to prove discovery. In September 2015, LIGO had returned to data taking after an extensive upgrade. Almost immediately, the team of scientists observed the unmistakable signal of two massive black holes inspiraling and merging over one billion light years away from the Earth. The results published on Thursday only contain information from the first month of data taking, so physicists know that there will be more exciting data in the pipeline.
The announcement goes far beyond simply observing gravitational waves. LIGO has opened up an entirely new way to observe the universe. Every time astronomers have found a new technique to view the sky, they have been surprised by objects like pulsars (from radio waves), black hole accretion disks (from x-rays), and gamma ray bursts. The potential for further discovery is tremendous. With more data, and more detectors like LIGO planning to go online soon, there is no question that our understanding of black holes is about to be revolutionized. All LIGO has to do is wait and see what other secrets the universe has to share.
Acknowledgements: Many thanks to Michael Coughlin and Andrew Chael, PhD students in the Harvard Physics Department working at the Harvard Smithsonian Center for Astrophysics.
Original Article: Observation of Gravitational Waves from a Binary Black Hole Merger – PRL
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