Janna Levin

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... black holes, curve space and time around them, in the way that we've been describing, things fall along the curves in space. If the black holes move around, the curves have to follow them, right? But they can't travel faster than the speed of light either. So what happens is black holes, let's say move around, maybe I've got two black holes in orbit around each other, that can happen. It takes a while. A wave is created in the actual shape of space, and that wave follows the black holes as black holes are undulating. Eventually those two black holes will merge. And as we were talking about, it doesn't take an infinite time, even though there's time dilation because they're both so big, they're really deforming spacetime a lot. I don't have a little tiny marble falling across an event horizon. I have two event horizons, and in the simulations you can see a bobble and they merge together and they make one bigger black hole. And then it radiates in the gravitational waves. It radiates away all those imperfections and it settles down to one quiescent, perfectly silent black hole that's spinning. Beautiful stuff. And it emits E equals MC squared energy. So the mass of the final black hole will be less than the sum of the two starter black holes. And that energy is radiated away in this ringing of spacetime. It's really important to emphasize that it's not light. None of this has to do literally with light that we can detect with normal things that detect light. X-rays, form of light, gamma rays are a form of light, infrared, optical. This whole electromagnetic spectrum, none of it is emitted as light. It's completely dark.