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Green plants reverse entropy?

  1. Oct 13, 2008 #1
    Entropy is said to always increase. But do not green plants reverse
    entropy? Seems to me that everything they do increases order, down to
    the molecular level.
     
  2. jcsd
  3. Oct 14, 2008 #2
    On 12 Oct, 20:12, e...@flesch.org (Eric Flesch) wrote:
    > Entropy is said to always increase.  But do not green plants reverse
    > entropy?  Seems to me that everything they do increases order, down to
    > the molecular level.


    No, the entropy of the Sun increases. Hydrogen is converted into
    helium. Everyone should read mark and inwardly digest. This is one of
    the arguments put forward against Evolution, that entropy decreases.


    - Ian Parker
     
  4. Oct 14, 2008 #3
    On Oct 12, 3:12 pm, e...@flesch.org (Eric Flesch) wrote:
    > Entropy is said to always increase.  But do not green plants reverse
    > entropy?  Seems to me that everything they do increases order, down to
    > the molecular level.


    All living things tend to decrease their own entropy. But the second
    law of thermodynamics suggests that, since entropy of the entire
    closed system must increase, they are increasing the entropy of their
    environment even moreso than they are changing their own. This makes
    sense in that living things require inputs of energy from the world
    around them to survive. Without those energy inputs, they would die
    and end up in a state of ever increasing entropy very quickly.
     
  5. Oct 14, 2008 #4
    Eric Flesch <eric@flesch.org> wrote:

    > Entropy is said to always increase. But do not green plants reverse
    > entropy? Seems to me that everything they do increases order, down to
    > the molecular level.


    No.
    In the proces: Photons + molecules -> other molecules + some heat
    there is a net increase of entropy,
    (unless you forget about the photons)

    Jan
     
  6. Oct 14, 2008 #5
    Eric Flesch wrote:
    > Entropy is said to always increase.


    A truly terrible approximation of the 2nd Law. A few minutes on Wiki
    would give you the proper definition and perhaps an understanding of why
    your example presents no difficulties.

    > But do not green plants reverse
    > entropy? Seems to me that everything they do increases order, down to
    > the molecular level.


    Yes, but with considerable input of energy. If you like, you could
    consider the entropy loss well and truly paid for by entropy increase in
    the sun.
     
  7. Oct 20, 2008 #6
    Eric Flesch wrote on Sun, 12 Oct 2008 19:12:11 +0000:

    > Entropy is said to always increase.


    This is only valid if the system is isolated and not in equilibrium.

    In general, the entropy of a body can increase, decrease, or remain
    constant.

    > But do not green plants reverse
    > entropy?


    Contrary to some misconceptions propagating in creationists literature,
    living organism follow the second law.

    A living organism is an instance of dissipative structure. Since they
    are not isolated (interchange matter and energy with surroundings)
    its entropy is not forced to increase. In fact, a mature organism is
    one for which its entropy is almost constant.

    > Seems to me that everything they do increases order, down to the
    > molecular level.


    Due to bad textbooks there is additional confusions regarding the
    concept of 'order' described by statistical entropy

    S_inf = k ln W,

    the concept of spatial order, and the concept of thermodynamic entropy

    S_th = (U + pV - muN) / T.

    Several of those confusions are also the basis for creationists
    (unfounded) attacks on science.

    For a more detailed discussion of the relationship between living
    organism and the second law of thermodynamics see

    http://canonicalscience.blogspot.com/2008/05/second-law-of-thermodynamics-living.html

    and references cited therein. If you are really interested on the
    thermodynamics of living bodies I recommend you the textbook on
    biological thermodynamics.

    --
    http://www.canonicalscience.org/en/miscellaneouszone/guidelines.html
     
  8. Jun 18, 2011 #7
    I believe that all forms of life can be considered examples of reverse entropy in and of themselves, however they are not closed systems. All forms of life rely on external sources of energy in order to maintain their complex organization. Even then they eventually die. Death might result from an overload of outside energy or it may simply be entropy catching up with a temporary exception to the rule.

    The main point is that in order to reverse entropy or even create the illusion of such a reversal, energy must be expended from another system whose entropy level will be increasing to such an extent that the overall result will still be a degeneration of the complexity of the universe.
     
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