I'm a total physics n00b (i.e. I only know the physics as taught in IT grades, and don't remember much of it), and was talking about entropy (initially, not with the physical implications). My friend talked about entropy and gravity and was not sure about the fact that entropy decreases with gravitationally bound systems.
I found this site telling that gravity actually increases the entropy, but "apparently proving" that gravity decreases it. Finally, in the final link where he will show the prove that gravitational systems do not decrease entropy, it shows this text:
So, you're wondering why gravity doesn't violate the 2nd law of thermodynamics, even though the entropy of a gas cloud decreases as it shrinks under its own gravitational pull? The answer is simple, but I'll just give you a hint. We've already seen that as it shrinks, it loses energy. The energy has to go somewhere. Where does it go? If you figure that out, you'll see that the total entropy is not actually decreasing - it's just leaving the gas cloud and going somehere else!
My question is: No, actually I cannot figure if out. Can someone help me to figure it out? (yes, perhaps it's a very simple answer but no, still don't get it).