I thought that one of the leading theories of white holes is that they exist somewhere beyond the point of singularity within a galactic supermassive black hole and that the energy released expands into an entire new universe (The Big Bang).

But both that theory and the Einstein-Rosen bridge theory were both accepted by Hawking and other notable theoretical theorists. How could you use a white hole for time travel within your own universe if it’s actually a ‘gateway’ to an entirely different universe?

Am I being retarded or are these completely conflicting theories? Am I misunderstanding something?