On September 14, 2015 at 09:50:45 UTC, for the first time in history, the two detectors of the Laser Interferometer Gravitational-Wave Observatory both observed a transient gravitational-wave signal. Based on previous simulations of possible observations, the Ligo Collaboration Team was able to conclude that what their revolutionary experiment had detected was the result of two black holes merging 1 billion years ago.
Not since Galileo first turned a telescope on the night sky in 1609 have men taken such a profound step forward in observing the universe. But, whereas all telescopes since Galileo have been limited to using electromagnetic waves at one of it’s many frequencies, Ligo’s observations are based on an entirely different principal: it uses the distortions of space-time itself to make deductions about what caused these distortions. In this case, the movement and final fusion of two massive black holes.
The signal that they observed was a mere 20 millisecond blip.For the layman it might seem strange to think that the astronomers are not actually seeing anything concrete, but merely comparing a tiny observation with computer-based predictions and thereby coming to dramatic conclusions.
But this is the way that cutting-edge science works. It is exactly the same at CERN, for example, and many other physics experiments.
This is just the beginning of a revolution in astronomy. Know we know that laser interferometry really can detect gravitational waves, scientists will be pressing governments for the money to build more, bigger and more sophisticated observatories. And just as Galileo could never have predicted the discoveries to which his first observations have led us in the past 400 years, so we have no idea what incredible new things we are going to learn about the universe. But results are certainly not going to take another 400 years to arrive.
For more information see the following:
A summary of the scientific paper carrying the announcement:
A podcast of a 30 minute BBC radio program on the day the discovery was announced http://www.bbc.co.uk/programmes/b06zj4dl
A BBC news story with useful images
A Scientific American Feature on the story