Not a lot of people know that black holes have an antonym, the white hole. The white hole is basically the reversal of the time of a black hole. As a black hole has matter at seeming random going into it without predictability, the white hole has such matter coming out of it. (and matter cannot enter it) a white hole is a singularity for that reason. When people talk about the big bang theory they are talking about a white hole, for example. (ie., you can make a new universe from whats called a false vacuum bubble in terms of relativity
BUT it would require a white hole singularity.) Why is this important? Because in principle this cant happen or be made to happen. BUT the false vacuum bubble could expand to be a new universe through the process of quantum tunneling.