Why does entropy always increase?

Question

I'm a physics major so if you could explain in a logical manner and include some proofs that would be helpful.

Answer 1

Entropy is a measure of a system disorder. Any isolated system doesn't increase it's order. It is statistical regularity for systems consisting of MANY objects (it's hard to define what "order" is, for systems consisting of a few objects).
It's always easier to destroy than to build.

Answer 2

You asked for it, physics major, so here it is (sans proof). Entropy is the log of the multiplicity (number) of microscopic quantum states accessible to a system consistent with its macroscopic description (volume, energy content, mass, pressure, etc). In stat mech, it is assumed that if you wait long enough, all of these states have equal probability. When that occurs, the system is referred to as being in thermal equilibrium. It can be proved from the above that this equilibrium has the maximum entropy possible vs. a macroscopic partitioning of the system into smaller subsystems with an arbitrary redistribution of the extensive conserved properties. The proof is left to the reader.

Answer 3

In a most basic level: Because the time is running, it does not stop or reverse. So, if you can manage the answers about what TIME is (of course it is not just "a fourth coordinate" or maybe not at all) then you will resolve the question of entropy.

Answer 4

that question is just like asking "why the universe always expands"

the constant expansion of the universe is actually the effect of increasing entropy =)