Today, scientists announced that they have — for the second time — observed the gravitational waves produced by ancient orbiting black holes with the help of the Laser Interferometer Gravitational-Wave Observatory (LIGO).
Just as sound waves disturb the air to make noise, gravitational waves disturb the fabric of spacetime to push and pull matter as if it existed in a funhouse mirror. If a large gravitational wave passed through you, you’d see one of your arms grow longer than the other. If you were wearing a watch on each wrist, you'd see them tick out of sync.
When two black holes collide, they unleash a massive wave of gravitation. But by the time they reach Earth 1.4 billion years later, those waves have become very faint (like how the ripples from a stone dropped in a pond mellow out the further you get from the stone). You can actually take a listen to these gravitational waves here:
Because the waves LIGO detect have a frequency that’s comparable to the range of frequencies we can hear, scientists can pump up the volume and translate them into sound. (Yes, this isn’t exactly what it sounds like, but rather an audio representation of the data. And, yes, the event would have made no noise in the vacuum of space.)
In this video above, the LIGO scientists compare the sounds created by this most recent discovery with their first one back in February. And as you listen, think about this: You’re hearing remnants of black holes that collided into each other some 1.4 billion years ago, in a galaxy far, far away. It’s the music of the cosmos.