So, why all the hubbub about gravitational waves?

Physicists were all abuzz in February 2016 with a universe-shaking announcement: Scientists had detected the sound of two massive black holes smashing into one another, forming a new black hole nearly twice as big.

The sound came in the form of a brief burst of gravitational waves, vibrations that radiated from the collision-like ripples spreading on a pond, traveling more than a billion light-years before they reached Earth. This was the first time in history that anyone had directly detected gravitational waves.

Simulation of two merging black holes. (Credit: Werner Benger/NASA Blueshift/Flickr)

The hypersensitive antenna that picked up the sound, a brief chirp that lasted a fraction of a second, is the Laser Interferometer Gravitational-Wave Observatory (LIGO). LIGO is actually two separate antennas, one in Hanford, Washington, the other in Livingston, Louisiana.

Each consists of a pair of 2.5-mile tunnels at right angles to each other, down which researchers shoot laser beams and measure their reflections in order to detect tiny movements. Boston University physicist Andrew Cohen talked with university writer Neil Savage in March 2016 and explained what LIGO found and why scientists are so excited.

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Author: Boston University
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