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Thermodynamics is the study of the conversion of heat energy into other forms of energy. In our lesson on thermodynamics we learned the three laws of thermodynamics. They are not always obvious or intuitive: without careful study it is easy to misunderstand their implications.
In particular, many people have misconceptions about the 2nd law of thermodynamics. One common question is “Does the Big Bang theory violate the second law of thermodynamics?”; click the link for a discussion on that topic.
Another question which often arises is “Does evolution violate the 2nd law of thermodynamics?”
We’ll address that question here, with a discussion from Five Major Misconceptions about Evolution, © 1995-1997 Mark Isaak
This shows more a misconception about thermodynamics than about evolution. The second law of thermodynamics says, “No process is possible in which the sole result is the transfer of energy from a cooler to a hotter body.” [Atkins, 1984, The Second Law, pg. 25]
Now you may be scratching your head wondering what this has to do with evolution. The confusion arises when the 2nd law is phrased in another equivalent way, “The entropy of a closed system cannot decrease.”
Entropy is an indication of unusable energy and often (but not always!) corresponds to intuitive notions of disorder or randomness. Creationists thus misinterpret the 2nd law to say that things invariably progress from order to disorder.
However, they neglect the fact that life is not a closed system. The sun provides more than enough energy to drive things. If a mature tomato plant can have more usable energy than the seed it grew from, why should anyone expect that the next generation of tomatoes can’t have more usable energy still?
Creationists sometimes try to get around this by claiming that the information carried by living things lets them create order. However, not only is life irrelevant to the 2nd law, but order from disorder is common in nonliving systems, too:
* sand dunes
* graded river beds
* and lightning
are just a few examples of order coming from disorder in nature; none require an intelligent program to achieve that order.
In any nontrivial system with lots of energy flowing through it, you are almost certain to find order arising somewhere in the system.
If order from disorder is supposed to violate the 2nd law of thermodynamics, why is it ubiquitous in nature?
The overall direction of change in the universe is from less probable (more organized) states to more probable (less organized) states. Life does not “oppose” this but rather makes use of it. The “downhill” movement can be used to raise things “uphill” (just as water flowing downhill through a water wheel can be used to raise a weight). There is, however, always a net loss of organization in the process.
For life on earth, the dissipation of energy from the sun is the downhill movement. Photosynthesis creates “uphill” molecules which in turn can be used in cellular respiration to create additional “uphill” molecules from which, in turn, all of the “uphill” organization of life and culture derive.
All of biological and human organization represents a state of improbability very much less than that of the concentration of energy in the sun, and one which would quickly dissipate if the sun ceased shining (or there was some disturbance in the chain of water wheels which link the sun to biological and cultural organization).
Q: Why doesn’t life and evolution violate the second law of thermodynamics? Don’t living things reverse entropy?
Posted on March 24, 2013 by The Physicist