I'm writing a sci fi book. I'm working with the theory that the singularity inside of a black hole is the big bang for another universe. A white hole. In my book, the reason why all of our physical constants are so perfectly tuned is because it was designed that way. Our entire universe is the product of an alien race who wanted to make a universe more fine tuned than theirs.

In our parent universe, light moves a million times faster.

Instead of taking 100,000 years for light to cross a galaxy the size of the milky way, it would only take a month.

Would this universe me a million times bigger than ours?

What other constants would need to be changed in order to make things stable, and make life possible?

Would there be any weird side effects to this?

This is an insanley hard thing to research, so if anyone has any suggestions on how I can get educated answers to these ridiculous questions, I would be very grateful!