Consider the for us observable Universe (the entire Universe is many orders larger). It is (I think) common knowledge that the Schwarzschild Radius (SR) exceeds the radius of our observable Universe (extending into the surrounding part of the entire Universe), which can one make conclude that we're living in a black hole.

But if we consider the entire Universe (under the assumption that the entire thing is large scale homogeneous and asymptotically flat), there should by this reasoning co-exist many (an infinity) of these kinds of black holes. At every point in the Universe, there is an SR, larger than the observable space seen from there, surrounding this point.

My question: Is it because of the entire (homogenous) Universe that the black holes like the one we (or creatures on faraway planets) allegedly live in (allegedly) don't exist (the entire Universe obviously can't have an SR).

But if the answer is "No", then what constitutes the singularities in these black holes?

  • $\begingroup$ We live in a white hole, not a black hole. $\endgroup$ – safesphere Apr 12 at 6:11
  • $\begingroup$ In Wikipedia: In general relativity, a white hole is a hypothetical region of spacetime which cannot be entered from the outside. Can mass enter the observable Universe from outside? I guess the answer is yes when you are finding yourself just outside the for us observable Universe even though the edge of the observable is receding at the speed of light (a lot of matter enters our observable Universe). But that's not the most important issue. I asked if the entire Universe is preventing the observable Universe to become a black hole. o you mean the entire Universe is a white hole? $\endgroup$ – descheleschilder Apr 12 at 12:46
  • $\begingroup$ Yes, the entire universe that could be, for example, an Oppenheimer-Snyder white hole with the singularity of the Big Bang. This is just an example, but in any case, there is only one singularity, the Big Bang, and it is of the white hole type. A white hole singularity is the beginning of time. A black hole singularity is the end of time. (Assuming spacelike singularities.) A Big Crunch would be a black hole type of singularity, if the universe started collapsing instead of expanding. Also, there is no experimental evidence of the "observable universe" concept. It is just an artifact of FLRW. $\endgroup$ – safesphere Apr 12 at 13:32
  • $\begingroup$ A white hole singularity is the beginning of time. A black hole singularity is the end of time. I like thát one! $\endgroup$ – descheleschilder Apr 13 at 11:57

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