Originally Posted By: Bill S.

Does this mean you disagree with the idea that the Universe might have expanded by several orders of magnitude in a very small fraction of a second?

I think that such an expansion is not possible. The expansion starts with maximum acceleration, eventually, the acceleration reaches zero and after that there is negative acceleration. The speed of expansion will be maximum when acceleration is zero.
Originally Posted By: Bill S.
So, a perfectly reversable change is one that is never completed?

That is, the system will always be in equilibrium, and so the change cannot go in any direction, unless there is some potential state which favours a change in a particular direction. As the process continues in that direction, the potential state decreases, and another potential state exactly opposite to the initial state is created. As a result the process stops, and the reverse process starts (like a pendulum oscillating).