I come bearing big news! Really big, out-of-this-world, black-hole sized news! On Thursday, Feb. 11, a team of scientists announced that they had heard and recorded the sound of two black holes—located one billion light-years away from Earth—colliding. This little chirp, which sort of sounds like something your phone would make to let you know your text was sent, is the first definitive evidence of gravitational waves, the last piece missing from Einstein’s general theory of relativity.
I am particularly excited to be reporting on this topic since I wrote a piece on the September updates to the Large Interferometer Gravitational-Wave Observatory (LIGO) in the Oct. 9, 2015 issue of TSL. It was those updates that allowed the Observatory to extend its search further into the depths of space and pick up that chirp. So, I’m pretty excited that I was able to follow along with the search. But you know who else must be pretty excited about this discovery? Albert Einstein, who predicted the existence of gravitational waves 100 years ago.
Unless you happened to have read my previous article, or unless you are a physics nerd, you might not know what a gravitational wave is. So, I’ll briefly explain what exactly these waves are and what their discovery means for us.
We see everything in the world through visible light, or electromagnetic waves. Protons, electrons, and basically anything with a charge emits and interacts with light. However, approximately 96 percent of the matter in the universe does not actually interact with light. This material—invisible to us—is dark matter.
Now, with the concept of dark matter in mind, here is a quote from my previous article explaining Einstein’s original theory concerning the existence of gravitational waves:
“Imagine now a sheet held very tight so it looks flat. Now put two oranges in the sheet, and watch (or imagine, I suppose) how the fabric dips down under their weight. That sheet is the fabric of space-time, and those two oranges are stars. Einstein predicted in 1915 that as those two stars move around each other and distort the space-time fabric, they will create a ripple moving outwards. Those ripples, which, at the speed light according to Einstein, are the gravitational equivalent of electromagnetic waves (aka light). We could, theoretically, use those gravitational waves to see dark matter and dark energy.”
And this is where LIGO comes in. There are two LIGO facilities, one in Louisiana and the other in Washington state, and they work in tandem to detect waves. Interferometers work by sending a laser beam through a beam splitter, allowing half of the beam to continue straight and reflecting the other half at a 90 degree angle. The beams move in straight arms, and then are reflected back together by mirrors. When these beams meet again, they create a bullseye-shaped interference pattern.
However, if one of those beams happened to be shortened by, for example, a gravitational wave, it would travel at a different speed than its other half and cause the interference pattern to change and prove Einstein’s theory. That is exactly what happened last week and resulted in LIGO’s momentous discovery.
You may be wondering who cares about this. Well, for starters, the National Science Foundation cares quite a bit, as they invested $1.1 billion dollars over 40 years into constructing and renovating these observatories. The team of researchers working on the project also care, given how much of their time they have dedicated to the project.
But this discovery is important for the entire scientific community because it is the only direct evidence they have so far for the existence of binary black hole systems. The scientific community had previously only attained indirect evidence of such systems in the form of X-rays from matter falling into other black holes and the distortion of the orbits of stars at galactic centers that host massive black holes.
Furthermore, this discovery allows scientists to move forward in their exploration of the 96 percent of matter in the universe that does not interact with light. They can also begin their quest to explore, in the words of Kip Thorne, Caltech’s Richard P. Feynman professor of physics, “the warped side of the universe—objects and phenomena made from warped spacetime. Colliding black holes and gravitational waves are our first beautiful examples.”
So, let us give a big round of applause to Einstein, who was truly a man ahead of his time.