>>13448326It's true that on a fundamental level time is nothing but a parameter and -- more interestingly -- all of the known fundamental dynamical laws are actually time reversal invariant. So in this sense it is indeed not clear why time "passes" and is not something similar to space, where one can go back and forth as he wishes.
Things change however, when you consider the unbelievable number of degree of freedoms in the macroscopic world. It is an interesting observation that systems consisting of large number of d.o.f show time _irreversibility_, even though the underlying (quantum) mechanical laws might be symmetric under time reversal. This is where statistical physics (including thermodynamics) comes into play and one should consider a quantity that is known from information theory, the entropy. It is reasonable to assume that the "passing of time" is deeply connected to information theoretical concepts.
See also
https://en.wikipedia.org/wiki/Entropy_(arrow_of_time) and references therein.
