Comment by pdonis

> the Big Bang would be the white hole horizon (i.e. a singularity in out past)

The white hole horizon is not the same thing as the white hole singularity. The "Big Bang" as an initial singularity in our universe (which is not actually the correct usage of the term "Big Bang", but that's a whole other discussion) would be the white hole singularity, not the horizon.

Note also that in a white hole model of our universe, we would be inside the white hole horizon, not outside it.