“Ladies and gentlemen, we have detected gravitational waves. We did it!” When LIGO’s executive director, David Reitze, announced these words in a live feed from the Laser Interferometer Gravitational-Wave Observatory (LIGO) on Thursday afternoon, he couldn’t have sounded more triumphant. Not that he should have sounded anything but, of course, for this discovery, as Reitze goes on to remind his audience, is equally as important as the moment Galileo turned his telescope to the skies.
This, I’m sure you’ll agree, is quite a tremendous claim. So what is it that makes this discovery so special? It starts with the equipment designed by the physicists: a 4km strip of laser beam and a mirror, capable of detecting a distortion in spacetime a thousandth the diameter of one atomic nucleus. The scientists themselves have spent over 25 years perfecting this piece of equipment, and months toiling over the data, waiting for a fluctuation which would indicate the presence of gravitational waves.
Another aspect which makes this discovery so special is that it is largely based on the predictions made by Einstein 100 years ago. In 1916, he published his Theory of Gravitation which suggested that distortions in the geometry of space should propagate into the depths of space as gravitational waves, and that if enough mass is concentrated in a given location, a geometrical prism, or a black hole, should form. This is yet another example in which advanced technology allows us to collect evidence for a century old theory!