system
Given the following post, respond as if you're commenting on Reddit:
human
From a mathematical perspective, why can't white holes exist?

Could someone explain precisely why physicists so fiercely dismiss the concept of white holes as a possibility, when they are a direct(ish) implication of Einstein's theories of relativity? Is there any mathematical theory that disagrees with the concept in any way? 

The Higgs Boson only ever existed theoretically, but it's recently been discovered (they're 99% sure now) thanks to technological advances at CERN. It seems to me that in dismissing white holes, we are dismissing ideas that we can't even begin to test, when extrapolating from accepted theories (like relativity) is our only available means of providing any tangible glimpse into the great mystery of the black hole.

I saw a video that said they couldn't exist because they would violate the second law of thermodynamics, but white holes are in some small sense implied by black holes aren't they, and don't all of our standard rules sort of break down inside the event horizon of a black hole anyway? So if the second law somehow supercedes what we expect to happen in a singularity, how does it do so?

Speculatively, is it possible that at the singularity of a black hole, spacetime is broken down completely and the matter falling in reappears (dismantled beyond recognition by the tidal forces) at the big bang at the very beginning of the universe?

I've recently gained a profound interest in the happenings at the very limits of our universe: the Big Bang, black holes, the infinitesimally small (quantum) and the infinitely large (outside the observable universe). I've also been looking at the zany suggestion of a fractal universe, which has been suggested from both small-scale and large-scale theories. I'm in the second year of a mathematics degree so at least to me, an 'undefined point' in our universe seems perfectly analogous to an undefined point for a simple function, so why should a mathematical assertion for conditions within the *physical* universe be so unreasonable? It would be really awesome if you science people could provide some answers for my increasingly achey head!

P.S. I'm sorry if I'm not the first one to ask this but I've looked through a couple of the relevant questions and couldn't spot anything discussing exactly what I'm trying to find out.
gpt
It's not a mathematical prospective that forbids them to exist, it's that there's no process of stellar evolution that leads to their creation, nor is there any observational evidence of them.

You can however have an acoustic white hole, which you can make with your sink.