In the land of hypothetical physics there exists white holes, but it doesn’t get discussed much due to their sheer complexity. I won’t lie, I don’t understand them either, but I still want to write about them! These interesting objects are extremely similar to the black hole, and today we’ll discuss what they are.
The white hole sprung from a solution to Einstein’s field equations, specifically the Schwarzschild metric (this just describes the way gravity acts around a spherical mass). A white hole is a small area in space where light and matter can’t enter into but can escape from. It essentially works like a time-reversed black hole (hence the naming), where light and matter can enter but can’t escape. These objects would need to have some mass, maybe angular momentum and possibly charge, just like a black hole.
That sounds a bit suspicious, right? Surely there’s a finite amount of matter within a white hole, and once that matter’s gone it will disappear or explode or just cease to exist. Some theorise that black holes and white holes are connected in more ways than just their name, and I mean that literally. If a black hole and white hole were connected in some way, the light and matter falling into a black hole could potentially feed the white hole. This would make a wormhole, specifically an Einstein-Rosen Bridge. Remember: we’re still in the land of hypothetical physics!
Where could we find them?
In other theories of gravity, such as the Einstein-Cartan theory, wormholes do exist! This theory plays on perception, because instead of a star collapsing into a black hole it collapses into a wormhole with a new-born universe on the other side. From our point-of-view (the parent universe) we see a black hole, but the baby universe sees a white hole only. Hence, we’ve had some theorise that a white hole is simply a big bang (or a small bang).
However, most physicists don’t really consider this evidence of their existence since white holes break a lot of laws. They would be highly unstable, since they repulse matter from inside but also attract matter from the outside. In addition, we have no mechanism that could create these white holes.
The truth is that there is no physics to explain their creation, nor their connection to the typical black hole. I would love to see some observational work in their favour, who knows what the future of astronomy has in store for us!