There are a lot of questions on this site about white holes, but none of them specifically answer my question. Most of these questions talk about observing white holes from outside, but do not talk about the possibility of observing a white hole from inside.
I have read this question:
These are the only questions talking about the possibility of being inside a white hole, but none of the answers give an explanation to my question about experimentally telling whether we were inside one.
We have just visually observed a black hole (M87) for the first time, and took a real picture of it.
It is conjectured that they cannot, and the only possible black holes are the hypothetical primordial black holes that existed from the very beginning of the universe.
Now as far as I understand, what we observed is not even a really formed black hole (nor a fully formed event horizon), because that never forms in a finite time when viewed from our frame here on Earth.
Equations of fundamental physics are usually time-reversible (particle physics is time-reversible in a CP or CPT sense, though) which means you can take a certain reversal of the solution of your equations to obtain another solution. A white hole is a complementary object to a black hole in this sense. Every particle in it's field behaves the same as a particle near a black hole only with a reversed arrow of time.
Since white holes are supposed to be time-reversed black holes, does this mean that (when viewed from our frame), these white holes never fully form either?
The proper view is that the universe itself is an inside-out black hole, with a cosmological horizon that surrounds us.
So there are a few things that come to mind:
black holes (event horizon) never form in a finite time for an outside observer, and space contracts/squeezes inside into a singularity (the singularity is the future)
white holes are time reversed black holes
white holes (event horizon) never form in a finite time for an observer inside, and space inside them expands like in our universe (the singularity is the past)
So based on the these, and the last answer, that says that our universe is an inside-out black hole, is it possible to tell experimentally if we are inside a white hole?
- Is it experimentally verifiable if we are a inside a white hole that never fully formed?