I have done a lot of thinking on that gravity basically is time, and i actually thought that i was the only one thinking that... If the universe expands in all directions, then perhaps the time/gravity itself expands aswell, perhaps it's the gravity/time that expands/goes forward that makes the rets of the universe expands aswell?
I mean, think of it, if time would start to go backwards, the universe would shrink again!
I never heard of white holes just before the supernova, but i suggest ashoka to don't say no, because physics is VERY strange and there's a lot that we don't know, unlike what our ''cheap school books'' say.
If there's some sort of Gravity wave when the star goes supernova, it's possible that the explosion makes the plane of gravity wobble upwards, thus not only making a white hole, but also enabling time travel forward in time! (if we could survive the intense energy) then the gravity wobbles downwards and forms a black hole.
Maybe, the white hole still is there, just that the forward motion of time has brought us to the other end of the hole(the black part), and if you jump in the black hole, you come out trough the white hole at the moment when the star go supernova?
So, thats a interesting thing. If we could survive the travel trough a singularity and then after that trough a supernova's core, then we could go back to any moment when a supernova happened ever!
It could also be a way of saving the human race. If we have engines capable of travelling enourmos distances, wecan just fly away a few galaxies from Earth, jump trough a black hole that is a few hundred millions old, and we find ourselves were the universe is younger, the rest of humanity is nothing to care about, or when even the mantis themselves were just small insects.
Now, this might be wrong, but remember that it might be true in another wave function!
All is possible according to the wave function theory! ^^