A voice from a billion years ago has finally been heard by humans for the first time and that voice tells scientists that once again, Einstein’s theory of relativity is true.
A team of physicists who can now count themselves as astronomers announced on Thursday that they had heard and recorded the sound of two black holes colliding a billion light-years away, a fleeting chirp that fulfilled the last prophecy of Einstein’s general theory of relativity.
That faint rising tone, physicists say, is the first direct evidence of gravitational waves, the ripples in the fabric of space-time that Einstein predicted a century ago. And it is a ringing (pun intended) confirmation of the nature of black holes, the bottomless gravitational pits from which not even light can escape, which were the most foreboding (and unwelcome) part of his theory.
This discovery is huge as the search for proof of gravitational waves has always been a mythological journey considering the technology we have had—up until now.
Nevertheless, scientists built two massive detectors to take a look. Known collectively as the Laser Interferometer Gravity-Wave Observatory (LIGO), the detectors are located in Washington state and Louisiana. They are separated by thousands of miles in order to detect ripples coming in from deep space as they pass through the Earth.
Each detector looks like a big L, made up of two tunnels 2.5 miles long. It's designed so that if a gravitational wave passes by, it will stretch space along one direction of the tunnel and squish space along the direction of the other. The stretching and squishing changes the tunnels' lengths by a tiny amount, and that change can be detected by lasers.
This project was completed in 1999 but did not begin to show its full promise for at least a decade. The instruments built to detect gravitational waves are so sensitive that figuring out what was noise (i.e. cars or the Earth trembling) and what it was they were looking for was elusive. Read more about this predictably Nobel Prize winning discovery here.
You can also watch the New York Times video about the history of this event below the fold.
For more community discussion go to DainBramage or FishOutofWater’s diaries on the subject.