the basic laws of physics work equally well forward or backward in time, yet we perceive time to move in one direction only - toward the future. why?
to account for it, we have to delve into the prehistory of the universe, to a time before the big bang (or at least the latest big bang....). our universe may be part of a much larger multi-verse, which as a whole is time-symmetric. time may run backward in other universes....
entropy - from order to disorder:
a raw egg does well to exemplify the asymmetry of time: a fresh one breaks easily, but a broken one does not spontaneously put itself together again, for the simple reason that there are more ways to be broken than not. in other words, the broken egg has a higher entropy.
why do we remember the past but not the future? to form a reliable memory requires that the past be orderly - that is, have a low entropy. if the entropy is high, almost all "memories" would be random fluctuations, completely unrelated to what actually happened in the past.