Comment by pdonis
Comment by pdonis 3 days ago
> we're all almost certainly inside a black hole
No, we're not. The universe is rapidly expanding. Equating the Schwarzschild radius for a given blob of matter with the event horizon of a black hole requires that the matter be static or collapsing.
The "black hole cosmology" models referred to in the Wikipedia article are misnamed. It is theoretically possible that our observable universe is a patch of a Schwarzschild spacetime, which is what the models referred to are asserting, but if it is, then, since the universe is expanding, it would be a patch of the white hole portion of the spacetime, not the black hole portion. And the "horizon" would be a white hole horizon, i.e., one from which the universe's expansion would eventually cause us to pass out of.
However, such a model is extremely unlikely because it has no way of explaining where the white hole horizon came from. A black hole horizon can come into being from gravitational collapse, but a white hole horizon would have to have been "built in" to the overall universe from the very beginning. Nobody has any reason to think that is actually possible, even if we have a theoretical mathematical model that includes it.
What if we're expanding because we are in a black hole that is being fed by a collapsing star or other object in a many orders of magnitude larger scale universe?
Of course these kinds of things are probably 100% untestable.