3 ms·

The second law of thermodynamics is intrinsically a statistical law.

• mulmen 9y ago
  I'm not a physicist and I probably could have phrased that a little better. The example of a bowl of soup randomly and unevenly changing temperature implies to me that the physical system behaves randomly which I do not believe it does.
  • klipt 9y ago
    Entropy can decrease, just with vanishingly small probability: https://en.wikipedia.org/wiki/Fluctuation_theorem https://en.wikipedia.org/wiki/Fluctuation_theorem
  • kgwgk 9y ago
    You don't have a detailed knowledge about the state of every molecule in the bowl soup and its environment, so you have to rely on statistical mechanics. And the current macroscopic state that you observe could correspond to a particular microscopical state that evolves in surprising ways. But the probability is so low that it just doesn't happen. To make things worse, quantum mechanics is intrinsically random (at least as far as we know) and having a detailed knowledge of the state of the system allowing for certain prediction of its evolution is impossible in principle (and not just in practice).