Could there exist white holes as a counterpart to black holes?

We put this question to Ben Allanach, Theoretical Physicist from Cambridge UniversityBen: They're are theoretical possibility as you can find out from solving Einstein's equations but if you actually look into them you can't really see how they would form. They seem to be unstable. They're like black holes but stuff comes out of them rather than the other way around. Chris: So they're the reverse?Ben: YeahChris: So would the stuff that came out be antimatter? Because in our universe all the stuff we can see is matter.Ben: It would be any matter and antimatter and light would come out. They're unstable so I don't think they can form.