[ArloWatson]

Multiple Big Bangs

I've got a layman's theory that there may have been other "Big Bangs" in the universe, but that they are farther than 15 Billion Light Years away, so we haven't detected them yet.

[PatrickHenry]

I've got a layman's theory that there may have been other "Big Bangs" in the universe ...

This notion has been around. But as you point out, even if they exist, we can't detect such distant objects. There being no evidence to support their existence, there is no reason for scientists to pay attention to them, or even to apply the term "theory" to the idea of their existence. "Conjecture" seems more appropriate.