So I was watching another Universe installment by the History Channel and they briefly touched on the subject of The Big Crunch theory - something about it simply being the opposite of the Big Bang in that the universe will eventually stop expanding and then contract back to that single point.

 

Is there any reason to believe the physical laws could change, even subtley, as a result of this contraction? For that matter, is it at all plausible that the physical laws have even subtley changed over the course of our universe's 13 billion year history?

 

In terms of fiction, that would seem interesting, but I'm betting it's short on scientific reasoning.

I'd suggest that depends on the origin of dark energy.

 

But no we believe that for the most part the physics has not changed much, which is why high energy physics is a way of looking at interactions that happened close to the big bang (in terms of time).

I think that the question of whether physical law has changed is basically unanswerable. We've been studying physical laws for what may be generously called 5,000 years. I would say that serious study hasn't been until the last 500 or so. If something like the gravitational constant isn't so constant but changes 1 ppm per millennium, we aren't going to find that out for a very long time, but such a change can obviously have an effect over billions of years. I think that assuming that what we call constants today are constants is the best assumption for the moment, but I don't think it is outside of the realm of possibility that the "constants" aren't exactly constant. Quite simply, we have only been studying for a very, very, very short time of the Universe.