In 1915, Einstein presented the general theory of relativity and mathematically predicted the possible existence of the black hole. At first it was just a mathematical possibility even Einstein didn't really believe in, but in more recent years the development of X-ray astronomy has provided enough indirect proof that the existence of black holes can be stated as fact.
As these observations and research make more progress, all sorts of theories have sprung up about the singularity in the middle of a black hole, but the one I find most fascinating is that "a white hole connects to a different universe". Those two hourais must've passed through the singularity to another dimension as well.
The singularity. A point of infinitely high gravity, zero mass and great mystery. Some even suggest that the universe we're in right now is actually inside a black hole. It sounds pretty insane, but since black holes seem to contain more energy than the entire rest of the universe, the idea that another universe could possibly exist there has a firm mathematical basis.
Things with a mathematical possibility have a possibility to exist.
It really makes you wonder what the heck our reality even is.