What evidence do you have for this?

I'm going to point out something very fundamental here: I am not assuming there isn't a god. I'm not saying it's impossible that God created the universe old. Sure, God is all-powerful and he could create an entire universe made of corn on the cob and we wouldn't know the difference. It's total nonsense to assume just because something is possible that automatically means it happened. 

When The Bible was written they didn't know what the stars were. We have a lot more knowledge now than they did when the Book of Genesis was compiled in the time of Moses. 

So which is more likely? That the immense cosmos we can view, with all of it's processes that take eons to occur was just created "mid way" or that logically we can assume that the universe is indeed old.

It had a beginning, and we don't know what was before it. I'm not saying "there is no God" I'm just saying Moses didn't have his dates right.