Archive for Sunday, March 26, 2006

Entropy example

March 26, 2006


To the editor:

In his March 23 article about the billboard on Interstate 35 and 151st Street, Dave Ranney reported about entropy arguments against evolution as given on a Web site and by David Penny. As Penny explained, "In nature nothing goes from order to order; it goes from order to disorder."

Since the general public may not know what "entropy" means in scientific terms, let's look at another form of the entropy statement: Heat flows from hot to cold. This is an everyday experience which anyone can verify. Yet everyone is familiar with a system in which heat does flow from cold to hot. It is called a "refrigerator."

What the Web site and Penny failed to mention in their argument is that the second law of thermodynamics applies to the universe as a whole. The reason the refrigerator is possible is because work is done by the motor to extract the heat, so the decrease in entropy inside the refrigerator (colder) is more than compensated for by the increase in entropy outside the refrigerator (hotter). This is why one cannot cool a room by opening the refrigerator door. Spontaneous order does occur in nature because of the temperature gradients set up by the sun which allows work to be done. Just ask the people in New Orleans and look at the organized structure of Katrina as a counterexample to the Penny "explanation" quoted above.

Kenneth S. Schmitz,

Kansas City, Mo.


yourworstnightmare 9 years, 8 months ago

Exactly right. This "entropy" argument against evolution has just the right ring of "sciency-ness" to it (with apologies to Steven Colbert) to seem plausible to those who do not know a lot about science. More demagoguery from the antiscience ID creationists.

Paul Decelles 9 years, 8 months ago

Yes. And the ability to believe that sort of creationist clap trap in the face of empirical evidience is a clear example of the sort of delusional thinking I was talking about yesterday.


You might enjoy my comments:

DuQuesne 9 years, 8 months ago

So, how long do we have to put up with this nonsense before creationists reach equilibrium?

Schuyler DuQuesne

gr 9 years, 8 months ago

As Schmitz pointed out, "This is why one cannot cool a room by opening the refrigerator door", the total useful energy is decreased. Keep in mind, refrigeration is contrary to natural systems and is a process put in place by intelligent beings. It would not be, "in nature". I doubt anyone would suggest that the "organized structure of Katrina" can now be seen, nor did Katrina put anything in order. "Just ask the people in New Orleans."

From the example given, pretending that no contructive work may be done is misinterpreting the thermodynamic law. Maybe a statement from a textbook would help:

"The second law of thermodynamics can be stated as follows: It is impossible to construct a heat engine that, operating in a cycle produces no other effect than the absorption of heat from a reservoir and the performance of an equal amount of work."

You can't break even.

I believe that is in support of the idea that order goes to disorder. But, that is what Schmitz said with the refrigerator example, so what's the point?

This is an attempt to rewrite physics - most likely by those who have not studied it. And that is what Schmitz and others are attempting to do or confuse with. Although not coming out and saying it, he is implying that the 2nd law says heat can flow from cold to hot. But, that's not true. It states heat will not flow "spontaneously" from a cold object to a hot object.

Maybe a clearer statement would be, "In any physical system, disorder increases naturally, and work always is required to reverse this trend".

KCgolfer 9 years, 8 months ago

gr (posted March 27) seems to think that human activites are immune to the second law (then why hasn't a perpetual motion machine of the secnod kind been patented to alleviate energy shortages). It is true that for ONE heat engine the statement heat does not flow from cold to hot. But a refrigerator is composed of TWO heat engines in which one is running forward and one in reverse. The entropy of the refrigerator system of both engines increases, in accordance with the second law. At least that is what my physics book tells me. Of course, one has to assume that refrigerators exit. The definition of "science" might be rewritten in Kansas, but the second law is not subject to whimisical changes in definition.

gr 9 years, 8 months ago

By me saying "You can't break even", doesn't sound like I would agree with a perpetual motion machine. Are you saying no work is done in refrigeration to reverse the trend?

Please explain what you mean.

KCgolfer 9 years, 8 months ago

Response to gr. Quite clearly the refrigerator does not "break even". The sum of the entropies of the two engines is greater than zero. The second law of thermodynamics applies to the universe, in that all changes either increase the entropy (irreversible processes) or remains the same (reversible processes). Clausius and Kelvin stated the second law in words, as did you. But Clausius and Kelvin recognized that the earlier work of Carnot gave a quantitative measure of entropy. The reversible Carnot cycle gives the zero change in entropy. My point about the perpetual motion machine was that one cannnot exclude human endeavores from the second law results, as you seem to want. As long as one performs work a region of the universe can experience a decrease in entropy if another region has a more-than-compensating increase. It is work,in the form of free enrgy, not entropy, that determines sponteneity, in open systems such as those in nature. For example, Nature spontaneously causes a decrease in the entropy of water every time it snows.The energy that sets up the gradients which cause the weather, and hence snow, comes from the Sun. Life also depends upon the Sun, so Life also is an open system and driven by gradients which can sustain entropy decreases by performing work with a more-than-compensating increase in entropy in the surroundings.

gr 9 years, 8 months ago

"Nature spontaneously causes a decrease in the entropy of water every time it snows."

Doesn't physics state that a substance changing to a solid state gives up heat?

KCgolfer 9 years, 8 months ago

Heat is definitely lost when water freezes, and it is this heat that contributes to the increase in entropy of the surroundings. The decrease in entropy in going from liquid to solid is more than compensated by the increase in entropy of the surroundings. Again, there are factors operating here that include more than just the entropy. The free energy drives this change, not the entropy. But the second law must still apply to the system plus surroundings, whether the system is "natural" or have a little bit of human construction behind it, or else it would not be a scientific law. Entropy arguments against the possibility of evolution fail to take system plus surroundings into account, and focus solely on the system. Attractive intreactions, such as between particles that cause liquids to become solid, can reduce the entropy of a system, but this effect is conveniently ignored in agruments that evolution (self organization)is not possible. In a similar way, biomolecules aggregate in a specific manner as dictated by the geometry of the moelcules and the type of interactions. So you are right, heat does escape to the surroundings upon aggregation of particles in what is referred to as "the system".

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