Explaining Arrow of Time with Entropy
Raskolnikov's comments are exactly right. If you want more detail, I wrote a pedagogical note on precisely this subject for the American Journal of Physics a while back: Evolution and the second law of thermodynamics
On top of what has already been said before, it's worth noting that there are several different kinds of "arrows of time" in Physics:
- Arrow of time;
- The physical basis of the direction of Time.
Sure, Entropy is one of them, but there are others. And the way they interact is not necessarily something that's very well understood and/or explained.
Remember that popular analogies are always missing some of the more rigorous and technical aspects — so, take them with a grain of salt. ;-)
PS: Forgot to mention this book earlier, it's quite a gem: Evolution as entropy: toward a unified theory of biology.