First theorized in 1916, the existence of gravitational waves is upending the world’s understanding of physics, and now after two massive black holes collided nearly 2 billion light years from Earth, astronomers from the LIGO observatory in Washington have detected some of those ripples in the fabric of space-time.
What are gravitational waves:
Think of throwing a rock in a pond, the impact creates a wave, ripples that then begin to spread rapidly. Now, the pond is empty space ( space-time ), but it’s like a fabric ( says Einstein ), so when you drop a rock on the fabric of space-time it causes ripples that travel at the speed of light.
Gravitational waves were something predicted by Albert Einstein all the way back in 1916 in his theory of general relativity. At the time he showed through math that massive objects orbiting each other ( like black holes ) would disrupt space-time so much that waves of distorted space would flow out of the source.
For a long time, many scientists believed that gravitational waves didn’t exist, because it is super hard to detect them. They are really tiny. Think about this, when gravitational waves hit earth, they’re going to stretch the space around our planet, but in such an insignificant matter that if there was, let’s say a 621 000 miles long ruler, for example, it will only stretch by the length of a single atom. ( Yeah, let that information sink in for a little. )
How did the science community detect those waves:
There are three LIGO ( Laser Interferometer Gravitational-wave Observatory ) detectors, two of them are in the United States, and one in Italy. With three detectors ( much like how a GPS can triangulate your position here on Earth ) you can pinpoint the location of the black hole 1.8 billion light years away.
Still, we are not speaking about actually “seeing” or “hearing” something with those detectors.
So, how did we do that?
When gravity comes from a distant place in the universe, it hits one of the detectors that is shaped like an “L” and jiggles it. When that happens there is an interference with the lasers inside that “L” shape, which indicates to the scientists that a disturbance in gravity has hit that detector. With those three detectors, a gravity telescope is possible.
With light telescopes you can see planets, radio telescopes allow you to see galaxies, a gravity telescope opens up the possibility of getting baby pictures of The Big Bang, or getting inside of black holes to see what happens to all these stars that fall in. It can open up a whole new realm of astronomy.