Universe in a Black Hole

[Pugdaddy]

I didn't want to hijack the Black Hole thread I was following, but something occurred to me. If we scale up the BH to an enormous size, our entire Universe could theoretically have crossed the EH and following a path to the singularity. Could that explain the expansion of space(dark energy) we observe in our Universe? And why Galaxies are racing away as the get further from our observation point and closer to the singularity? I have no idea even where to start on the math. I guess first would be to see how massive the BH would need to be? Then how space would need to curved so that light we see coming from he edge of our observable Universe would appear to be approaching from all directions. Is this a worthy project? Or an exercise in futility?

[CuriousStudent]

Stephen Hawkings theory around black holes has him saying that black holes would produce and discharge electromagnetic radiation which would cause it to shrink over time (that is, if I'm correct with quoting him somewhat). So if the universe is expanding, yet the black hole is shrinking, is where I'm getting confused.

Clear this up for me if you can.

[Pugdaddy]

A BH radiates energy or equivalently mass. The evaporation time of a black hole is proportional to the cube of its mass. So a BH that is swallowing universes could be taking in more mass than it radiates and getting larger or it could have reached an equilibrium of mass swallowed to mass radiated. Even if it wasn't taking in any mass it would still not shrink much over billions of years.

An observer in a swallowed universe, I am speculating, would see all matter moving away faster and faster the further is was from the observer as the matter moved toward the singularity. Spacetime would also be stretched towards the singularity. Since all paths lead to the singularity it would appear to an observer in the swallowed universe as if spacetime was expanding in all directions. I am still working on the details, which may not happen in my lifetime.

[J.C.MacSwell]

A BH radiates energy or equivalently mass. The evaporation time of a black hole is proportional to the cube of its mass. So a BH that is swallowing universes could be taking in more mass than it radiates and getting larger or it could have reached an equilibrium of mass swallowed to mass radiated. Even if it wasn't taking in any mass it would still not shrink much over billions of years.

An observer in a swallowed universe, I am speculating, would see all matter moving away faster and faster the further is was from the observer as the matter moved toward the singularity. Spacetime would also be stretched towards the singularity. Since all paths lead to the singularity it would appear to an observer in the swallowed universe as if spacetime was expanding in all directions. I am still working on the details, which may not happen in my lifetime.

Something ahead of or behind you on your path toward the centre would be getting further away, but everything else would be converging with you.

I would have to think about how it might appear, but I would expect directional distortions would be apparent.

[Pugdaddy]

Two things we observe. One is that all Matter is moving away at velocities that increase proportionally with distance. Two is that space itself is also undergoing an radial outward expansion.

If our Universe is inside a BH, and all the matter inside is being accelerated toward the singularity, then the horizon of our observable Universe would be the point at which the light is redshifted out of our perception. Wouldn't it appear as if everything is moving away from everything else?

We are, I think, reasonably assured that there is an expansion of space happening. We have added a new degree of freedom to explain it. Namely Dark Energy. We know that Dark Energy does not change as the Universe expands. It is entirely possible that it is completely constant in terms of an Energy Density(10^-8 ergs/cm^3). So is the expansion of the Universe a result of something in our Universe like Dark Energy? Or is this observed expansion due to space being drawn/stretched by the singularity of the BH our Universe has happened be swallowed by?

[Strange]

If our Universe is inside a BH, and all the matter inside is being accelerated toward the singularity, then the horizon of our observable Universe would be the point at which the light is redshifted out of our perception. Wouldn't it appear as if everything is moving away from everything else?

 

 

I can't see why. I would expect anisotropy. My understanding is that things ahead of you would be falling towards an event horizon that remains ahead of you. I would also expect things to be getting closer together. (Especially as the singularity is ahead of you in time, not space.) But I really don't know.

 

You would need to demonstrate your suggestion, mathematically, using the Inner Schwarzschild solution to the Einstein Field Equations.

 

 

 

We are, I think, reasonably assured that there is an expansion of space happening.

 

And that is a result of the same equations that describe black holes.

 

 

 

We know that Dark Energy does not change as the Universe expands. It is entirely possible that it is completely constant in terms of an Energy Density(10^-8 ergs/cm^3).

 

I thought it increased with expansion (that energy density is constant, as you say).