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Is the xxxxxxx in the universe increasing?

  1. Jan 16, 2007 #1
    Is the xxxxxxx in the universe increasing???

    I have been stuck on the question for so long........please can you see if you can help me out.:smile:

    Is the entropy in the universe increasing? If yes, when did entropy start increasing? if no, what is happening to entropy in the universe?

    Thank you very much for any help.
  2. jcsd
  3. Jan 16, 2007 #2


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    Entropy is always increasing with every interaction of energy in the universe. Entropy can either stay the same or it can increase. It can not decrease*.

    *Caveat: One form of the second law states that entropy can not be destroyed, but this is truly not a law. The probability of entropy decreasing is so small that it would take a very, very long time for it to ever happen. In other words, it is very safe to say that it will not decrease.
  4. Jan 16, 2007 #3
    Hi Fred,
    Correct me if I am wrong here, but I think there might be two more caveats (actually, boundary conditions) that might need to be added to quote the second law in its complete form:

    Entropy increases for a system that is:

    a) Isolated and
    b) Far from thermal equilibrium.

    I believe that when a system is at thermal equilibrium (and isolated) is the case you cited about entropy remaining constant. The reason I bring up condition (a) is because some folks can get confused by a control volume where local entropy decreases do occur (as a result of energy being added to the control volume).

    Am I off base here? :biggrin:
  5. Jan 17, 2007 #4
    I always remember talking about this in intro college physics with the example of a hard drive -- in a sense, the surface of the hard drive is decreasing in entropy (because the files have some "order" to them). However, the entropy of the universe is increased because of the fossil fuel being burned to generate the electricity -- the heat from the processor, etc. So local entropy can decrease, but the entropy of the universe increases as a result.
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