Janna Levin: prediction

Transcript context

…Okay, can we just linger on this? So what models do we have about what happens on the inside of the black hole at that moment? So I guess that one of the intuitions, one of the big reminders that you’re giving to us is like, Hey, we know very little about what can happen on the inside of a black hole. And that’s why we have to be careful about making… It’s better to think about the black hole as an event horizon.” But what can we know and what do we know about the physics of spacetime inside black hole? I don’t mind being incautious about thinking about what the math tells us. I’m not such an observer. I’m very theoretical in my work. It’s really pen on paper a lot. These are thought experiments that I think we can perform and contemplate whether or not we’ll ever know is another question. And so, one of the most beautiful things that we suspect happens on the inside of a black hole is that space and time, in some sense swap places. So while I’m on the outside of the black hole, let’s say I’m in a nice comfortable space station. This black hole is maybe 10 times the mass of the sun, 60 kilometers across. I could be a hundred kilometers out. That’s very, very close, orbiting quite safely, no big deal hanging out. I don’t bug the black hole. The black hole doesn’t bug me. It won’t suck me up like a… I don’t bug the black hole. A black hole doesn’t bug me. It won’t suck me up like a vacuum or anything crazy, but some … My astronaut friend jumps in. As they cross the event horizon, what I’m calling space. I’m looking on the outside at this spherical shadow of the black hole cast by maybe light around it. It’s a shadow ;cause everything gets too close, falls in. It’s just this, just contrast against a bright sky. I think, oh, there’s a center of a sphere and in the center of the sphere is the singularity. It’s a point in space from my perspective, but from the perspective of the astronaut who falls in, it’s actually a point in time. Their notions of space and time have rotated so completely that what I’m calling a direction in space towards the center of the black hole, like the center of a physical sphere, they’re going to tell me where they can’t tell me, but they’re going to come to the conclusion, “Oh no, that’s not a location in space, that’s a location in time.” In other words, the singularity ends up in their future and they can no more avoid the singularity than they can avoid time coming their way. There’s no shenanigans you can do once you’re inside the black hole to try to skirt it. The singularity. You can’t set yourself up in orbit around it. You can’t try to fire rockets and stay away from it, ’cause it’s in your future. There’s an inevitable moment when you will hit it. Usually for a stellar mass black hole, we think it’s microseconds. Microseconds to get from the event horizon to the-…

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