What We Know: Scientists find Einstein’s gravity waves

Today’s announcement of the detection of gravitational waves by the LIGO (Laser Interferometer Gravitational-Wave Observatory) Team hallmarks the beginning of a new kind of astronomy (see Physical Review Letters 116, 161102-1).

Gravitational waves are extremely faint ripples in the fabric of space and time that come from some of the most violent events in the universe. The news exhilarated astronomers and physicists. For them, it’s like turning a silent movie into a talkie because these waves are the soundtrack of the universe.

Szabolcs Marka, a physicist at Columbia University who is leader of the LIGO member Columbia Experimental Gravity Group, said you could think of it as “a cosmic microphone”. “The skies will never be the same”.

“Einstein would be beaming”, said National Science Foundation director France Cordova.

But gravitational waves are not light, they are a brand new communication medium that travel unimpeded through gas, dust and interstellar space.

Scientists said they can even estimate, based on the signal, that the two black holes were 29 and 36 times the mass of the sun.

Some physicists said the finding is as big a deal as the 2012 discovery of the subatomic Higgs boson, sometimes called the “God particle”. Some said this is bigger.

Astronomers have been studying gravity for centuries now, but our ability to test gravity has been restricted to small deviations from Newtonian physics.

Gravitational waves were predicted by Einstein in his general theory of relativity in 1915, the theory that proposed space-time as a concept.

The strongest waves are caused by the most cataclysmic processes in the Universe – two black holes colliding, massive stars exploding, or the very birth of the Universe some 13.8 billion years ago.

While scientists have previously been able to calculate gravitational waves, they had never before seen one directly.

What you want to tune into is the subtle little “blip” that interrupts the signal – believe it or not, that’s the actual sound of gravitational waves surging in frequency as the black holes collided. “We did it!” exclaimed LIGO executive director David Reitze to rousing applause. “This is just a start”.

“This is the holy grail of science“, said Rochester Institute of Technology astrophysicist Carlos Lousto. They concluded there was less than a 1-in-3.5-million chance they were wrong, he said.

Scientists mostly use the word “hear” when describing gravitational waves, and the data does, in fact, arrive in audio form. It is a great technological and scientific feat that shows the best of our civilization and our capabilities.

Each of LIGO’s twin facilities, one in Livingston, La., and the other in Hanford, Wash., includes two shafts arranged in the shape of an L, each arm of the L stretching 2½ miles long. About 1.3 billion years ago two black holes swirled closer and closer together until they crashed in a furious bang. About three times the mass of the sun was converted into gravitational waves in a fraction of a second – with a peak power output about 50 times that of the whole visible universe. The LIGO observatory involves two laser beam paths that are combined so that any shift along one path will produce a change in the way the other path interacts with it, at the level of the wavelength of laser light. The waves are a distortion of space-time. Kip Thorne, the Cal Tech physicist who co-founded LIGO and has been working on gravitational waves for more than half a century, said he kept the secret even from his wife until just a few days ago.

“This is not just about the detection of gravitational waves”, pointed out Dr. Reitze.