This would have blown Albert Einstein's mind: We now know what ripples in the fabric of space-time sound like.
On Thursday (Feb. 11), scientists with the Laser Interferometer Gravitational-Wave Observatory (LIGO) project announced that they had made history's first-ever direct detection of gravitational waves, mysterious phenomena first predicted a century ago by Einstein in his theory of general relativity.
LIGO's two detectors — one in Louisiana and the other in Washington state — recorded the space-time distortions caused by gravitational waves that were produced 1.3 billion years ago during the merger of two black holes.
LIGO records such distortions on a photodetector, based on how long it takes laser light to travel down both 2.5-mile-long (4 kilometers) arms of each L-shaped detector. But it's a relatively simple step to convert this information into sound waves, project team members said.
"We can hear gravitational waves. We can hear the universe," LIGO Scientific Collaboration spokeswoman Gabriela Gonzalez, a professor of physics and astronomy at Louisiana State University, said during a news conference Thursday.
"That's one of the beautiful things about this [detection]," she added. "We are not only going to be seeing the universe — we are going to be listening to it."
So, what do gravitational waves sound like? The original conversion to sound waves evokes the thump of a heartbeat, while an adjusted version designed to better accommodate the range of human hearing could be mistaken for a drop of water falling into a bucket.
That's just my opinion, of course; Gonzalez described the frequency-shifted version as a "chirp." You can come to your own conclusions after listening to the gravitational-wave signal in this video.
LIGO team members report the gravitational wave detection in a new paper published Thursday in the journal Physical Review Letters. You can read it for free here: http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.061102.
The LIGO project is led by scientists from the California Institute of Technology and the Massachussetts Institute of Technology, and funded by the U.S. National Science Foundation.