Using this law in
reverse, you can actually "
prove" the
big bang:
Since the entropy of the universe never decreases with time, and since friction increases entropy, the universe has less entropy the farther back in time you venture. Sooner or later, you will have a universe with no entropy -- that is, total order -- and infinite temperature. Total order cannot be achieved on a large scale, so the universe must also have been extremely small at that point. q.e.d. =)