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I've always wondered about the relationship between the future observable universe and black holes. Since space is expanding, far away objects that we now see w

by jules 7y ago

I've always wondered about the relationship between the future observable universe and black holes. Since space is expanding, far away objects that we now see will eventually move away from us faster than the speed of light so there would be no way to get at them any more. This seems similar to dropping yourself in a black hole: when you cross the event horizon you won't be able to get back to the objects outside of the black hole, unless they're dropping into the black hole too. Also, the bigger the black hole you drop yourself into, the less you'll feel it because the tidal forces become smaller. I wonder what you would see if our galaxy and surrounding galaxies were dropping into a super big black hole. Would the black hole take up more than 50% of the celestial sphere? Would everything then be moving away from us at an accelerating rate?

ivalm 7y ago
There would be strong anisotropy in our observation. Alas things are moving away from us in ALL directions.
- jules 7y ago
  Right, it would seem that they should only be moving away in one direction, and eventually we'd even see a difference between the forward and backward direction. However, I've heard people claim that eventually, all directions go toward the singularity?
  - Filligree 7y ago
    That's once you're inside the black hole, and not entirely true; "past" points outwards. I'll admit it's close enough to true. Which is not to that's how it would look. Photons are also falling, so you'd still be able to see the external universe even if the apparent direction it's in isn't traversable. (The photons are coming from the past. See above...)
    - Already__Taken 7y ago
      >"past" points outwards. I don't think that grasps space-time as one thing and why black holes are so mental. The event horizon is where the past no longer points outwards, that path is broken. There's no direction in space or time with which to point your space engine to escape. No time you could travel to were that is restored.

by jules 7y ago

ivalm 7y ago

There would be strong anisotropy in our observation. Alas things are moving away from us in ALL directions.

jules 7y ago
Right, it would seem that they should only be moving away in one direction, and eventually we'd even see a difference between the forward and backward direction. However, I've heard people claim that eventually, all directions go toward the singularity?
- Filligree 7y ago
  That's once you're inside the black hole, and not entirely true; "past" points outwards. I'll admit it's close enough to true. Which is not to that's how it would look. Photons are also falling, so you'd still be able to see the external universe even if the apparent direction it's in isn't traversable. (The photons are coming from the past. See above...)
  - Already__Taken 7y ago
    >"past" points outwards. I don't think that grasps space-time as one thing and why black holes are so mental. The event horizon is where the past no longer points outwards, that path is broken. There's no direction in space or time with which to point your space engine to escape. No time you could travel to were that is restored.