Astronomers on Thursday announced the detection of a gravitational wave, a phenomenon Albert Einstein predicted a century ago in his theory of general relativity. This is a big breakthrough in the world of physics. (Explained: What you need to know about gravitational waves)
Scientists mostly use the word "hear" when describing gravitational waves, and the data does, in fact, arrive in audio form. The researchers can don headphones and listen to the detectors' output if they want. On Thursday, to prove they found a gravitational wave, the researchers played a recording of the sounds.
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Gravitational waves sent out from a pair of colliding black holes have been converted to sound waves, as heard in this animation.
The Laser Interferometer Gravitational-Wave Observatory (LIGO), says that on September 14, 2015, it observed gravitational waves from the merger of two black holes, each about 30 times the mass of our sun. The incredibly powerful event, which released 50 times more energy than all the stars in the observable universe, lasted only fractions of a second.
In the first two runs of the animation, the sound-wave frequencies exactly match the frequencies of the gravitational waves. The second two runs of the animation play the sounds again at higher frequencies that better fit the human hearing range. The animation ends by playing the original frequencies again twice.
As the black holes spiral closer and closer in together, the frequency of the gravitational waves increases. Scientists call these sounds "chirps," because some events that generate gravitation waves would sound like a bird's chirp.
