Major news for the science world – and really, our universe – took place last week when scientists announced they’d detected gravitational waves. Waubonsee Physics Instructor, Dr. Pratima Jindal, sat down to explain to us why this is such big news.
Can you give us a little background on how this discovery came about?
Dr Jindal:
Einstein predicted gravitational waves in his general theory of relativity over 100 years back, the theory that proposed space-time as a concept.
The Light Interferometer Gravitational-Wave Observatory (or simply LIGO) collaboration announced the detection of gravitational waves coming from the merger of two black holes located somewhere in the Southern sky, in the direction of the Magellanic Cloud.
The two black holes- one 36 times our sun’s mass and the other 29 times sun’s mass - spiraled into each other merging into one black hole 62 times heavier than our sun!
The remaining mass - three times the mass of our sun - was converted into energy by Einstein’s famous equation E= mc2. This energy was carried across the universe by these gravitational waves that are a distortion of space- time.
So how did scientists actually perform this experiment?
Dr. Jindal:
LIGO is a system of two identical detectors - one located in Livingston, Louisiana, the other in Hanford, Washington, carefully constructed to detect incredibly tiny vibrations (approximately of the size of the nucleus) from passing gravitational waves.
The project was created by scientists from Caltech and MIT and funded by the National Science Foundation.
On September 14, 2015, the gravitational waves that were produced somewhere between 700 million and 1.6 billion light-years away reached Earth, where they changed the length of the LIGO arms by a very tiny amount; 1/1,000 the width of a proton.
Why is this measurement exciting?
Dr. Jindal:
There's been a lot of indirect evidence for their existence, but this is the first time we actually detect two black holes merging and we know the only thing that predicts that is gravitational radiation.
Imagine having never been able to hear before and all you can do is see. Now we can listen to the universe where we were deaf before.
It's a different spectrum (from the electromagnetic spectrum). It's unlike anything we've ever detected before.
What's really exciting is what comes next. This is opening a window on the universe - a new field of science called gravitational wave astronomy.
