"The only way that spacetime can evolve on its own is to be part of the physics of a larger 5-dimensional space with a second dimension of time in which it can evolve. That would be bizarre, since it suggests a past that is not static. But since this is not the case, spacetime merely "exists"...
I think you are on the right track. Independent estimates of the size and mass of our universe place it entirely within its own Schwartzschild radius, where the radial dimension and time switch roles due to a sign change in the metric. My theory is therefore that we are in a humongous Black...
I can't accept that the event horizon is not "a point in spacetime" We can and do assign coordinates to it, so it must be! However, I do have some grave doubts about its nature.
Here is one issue I am struggling to understand:
I think I am right in saying the gravity gradient at the event...