I'm going to promote this, but because this touches on several different but related topics I want to list what they are, just for clarity about what this thread's topic encompasses. The topics I see are:
Could the physical laws of the universe have been different in the past?
If so, could they have been different in such a way as to be undetectable by us today?
Could there be such a thing as an alternate reality that is undetectable?
If so, could a change in physical laws be effected from this alternate reality?