The Big Crunch and perceived entropy I'm aware of the Big Crunch theory, that once at capacity, the universe may collapse in on itself. Hawking once theorized that time may go backwards during this crunch. So, that got me thinking: how would we perceive backward time? 
That leads me a question: considering what we know about thermodynamics, relativity and entropy, is it scientifically plausible that the universe is not currently expanding, but is actually in the process of a Big Crunch, and that we are simply perceiving time as moving forward, kind of like the way your eyes see the world upside down but your brain corrects the image? 
What could the implications of this be? Would any phenomena that we've observed in the universe make more sense from the perspective of this theory?
 A: The Big Crunch is a prediction of the FLRW metric when the matter/energy density is above the critical value i.e. a closed universe. The FLRW metric gives us the scale factor of the universe as a function of comoving time, and for a closed universe the scale factor increases smoothly with time from zero at the Big Bang, through a maximum and back to zero at the Big Crunch. There is no sense in which comoving time reverses and runs backwards as we approach the Big Crunch.
The argument about time is usually related to the entropy of the universe. If the entropy started off as zero (or small) at the Big Bang, maybe it would reach a maximum at the maximum size then decrease again as the universe contracted towards the Big Crunch. Given that entropy generally increases with time, does this mean that as the entropy decreased towards the Big Crunch time, or maybe just our perception of time, would run backwards?
The problem with this idea is that there is no reason to suppose that entropy would decrease as the universe approached the Big Crunch. Quite the reverse really. In fact this is one of the arguments commonly made against cyclic universes, as without some mechanism to reset the entropy each cycle would have a higher entropy than the one before.
So your question can't be answered, because there is no reason to suppose that time runs backwards at the approach to a Big Crunch.
