4 ms·

What happens "inside" a black hole is basically unknown to this day. The fact that you cannot observe something entering a black hole (i.e. crossing the event h

by yoha 12y ago

What happens "inside" a black hole is basically unknown to this day. The fact that you cannot observe something entering a black hole (i.e. crossing the event horizon) does not help visualizing the situation.

sillysaurus3 12y ago
Here's something else I've always been curious about. It's a little bit unrelated to my first question, but I may as well ask. It's kind of a fun thought experiment. In order to answer the first question about living inside a blackhole, one could imagine dangling one's legs into an event horizon and then pulling them back out. If you can do that, then there's no firewall, and it's possible to live inside a black hole. This is obviously impossible, since nothing can come back out of an event horizon by definition. But now imagine slingshotting around a blackhole while dangling your legs toward it. Since nothing can escape an event horizon, your legs (or whatever you're dangling) would be ripped away as soon as they cross the event horizon, right? However, imagine getting very close to the horizon, but not actually crossing it. So, the question is: How fast would you need to be slingshotting around a blackhole in order to dangle something near the event horizon while still being able to retrieve it? Do you need to be going exponentially closer to the speed of light, with respect to how close you want to approach the horizon? Imagine a spacecraft with an extremely long pole sticking out of it. The spacecraft slingshots around the blackhole while dangling the pole towards it. What would happen if the tip of the pole crosses the horizon? Would it cause the whole spacecraft to get pulled in, or would the pole break away? This is probably a basic physics question, but sadly I'm not a basic physicist, as I've shown with my original confusion. It's quite interesting to realize no one will ever know whether it's possible to live inside a blackhole without jumping fully into one, at which point you'll never be able to tell anyone else.
- ChuckMcM 12y ago
  That is the thing about the event horizon, things that go in don't come out, ever. (except maybe as Hawking radiation) There is no speed in which you could approach the event horizon, go inside, and the come out again. It is, by its very definition a one way ticket.
  - sillysaurus3 12y ago
    Indeed. To be clear, I was trying to ask about the speed at which you'd have to travel in order to approach (but not enter) an event horizon. Say, a distance of one meter. Or one millimeter. Does your speed have to exponentially increase the closer you get?
    - bashinator 12y ago
      This isn't a direct answer to your question, but it might help. At 1.5x the radius of the event horizon, only photons can maintain a stable orbit around a black hole. If you get closer to a black hole than that, the only two options are to be ejected entirely (hyperbolic "orbit"), or to be captured and enter the event horizon. For objects with mass, this distance increases.
  - pmoriarty 12y ago
    Could gravitons or tachyons, if they existed, come out of a black hole?

by yoha 12y ago

sillysaurus3 12y ago

Here's something else I've always been curious about. It's a little bit unrelated to my first question, but I may as well ask. It's kind of a fun thought experiment. In order to answer the first question about living inside a blackhole, one could imagine dangling one's legs into an event horizon and then pulling them back out. If you can do that, then there's no firewall, and it's possible to live inside a black hole. This is obviously impossible, since nothing can come back out of an event horizon by definition. But now imagine slingshotting around a blackhole while dangling your legs toward it. Since nothing can escape an event horizon, your legs (or whatever you're dangling) would be ripped away as soon as they cross the event horizon, right? However, imagine getting very close to the horizon, but not actually crossing it. So, the question is: How fast would you need to be slingshotting around a blackhole in order to dangle something near the event horizon while still being able to retrieve it? Do you need to be going exponentially closer to the speed of light, with respect to how close you want to approach the horizon? Imagine a spacecraft with an extremely long pole sticking out of it. The spacecraft slingshots around the blackhole while dangling the pole towards it. What would happen if the tip of the pole crosses the horizon? Would it cause the whole spacecraft to get pulled in, or would the pole break away? This is probably a basic physics question, but sadly I'm not a basic physicist, as I've shown with my original confusion. It's quite interesting to realize no one will ever know whether it's possible to live inside a blackhole without jumping fully into one, at which point you'll never be able to tell anyone else.

ChuckMcM 12y ago
That is the thing about the event horizon, things that go in don't come out, ever. (except maybe as Hawking radiation) There is no speed in which you could approach the event horizon, go inside, and the come out again. It is, by its very definition a one way ticket.
- sillysaurus3 12y ago
  Indeed. To be clear, I was trying to ask about the speed at which you'd have to travel in order to approach (but not enter) an event horizon. Say, a distance of one meter. Or one millimeter. Does your speed have to exponentially increase the closer you get?
  - bashinator 12y ago
    This isn't a direct answer to your question, but it might help. At 1.5x the radius of the event horizon, only photons can maintain a stable orbit around a black hole. If you get closer to a black hole than that, the only two options are to be ejected entirely (hyperbolic "orbit"), or to be captured and enter the event horizon. For objects with mass, this distance increases.
- pmoriarty 12y ago
  Could gravitons or tachyons, if they existed, come out of a black hole?