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The simplest explanation of why we should care about gravitational waves

SXS / Calctech
Brian Resnick is Vox’s science and health editor, and is the co-creator of Unexplainable, Vox's podcast about unanswered questions in science. Previously, Brian was a reporter at Vox and at National Journal.

In February, when a team of scientists announced they had detected gravitational waves for the first time ever — a blockbuster, Nobel-worthy discovery — I called up Cliff Burgess.

Burgess is a theoretical physicist at McMaster University in Ontario. Throughout his career, he has authored hundreds of papers on the hardest problems in science: supersymmetry, string theory, wormholes, and dark energy, to name a few.

My question to him was simple: Why are astronomers and physicists so excited about this?

"It’s a whole new way of seeing the sky," he said.

He continued:

If you look with visible light as far as we can look in the universe, the universe is no longer transparent, it becomes opaque. There’s nothing you can do about that.

If you could see [gravitational waves], you can see back past where you can’t see with physical light. That would be cool. We’d have direct access to something that’s farther away than we can hope to see otherwise.

Typically, we can only see celestial objects that emit electromagnetic radiation — visible light, X-rays, gamma rays, and so on. But some objects — like colliding black holes or the smoking gun of the Big Bang — don't emit any electromagnetic radiation. They emit gravity.

And that's why, with this discovery, invisible objects in the universe may soon become visible. (Also, gravitational waves are unchanged by the matter they move through. Visible light can get absorbed or reflected by cosmic bodies or dust before it reaches our telescopes, leaving us with a cruddy view of things.)

On June 15, scientists announced they used gravitational wave detectors to make a second-ever observation of black holes colliding. More and more of these discoveries will come as more gravitational wave detectors come online.

What physicists are most excited about is not what they think they might observe with gravitational waves. They're excited for the things that will completely surprise them. We have a whole new way to see the sky. And that's cool.