Notice: 2ndlaw.com is now http://2ndlaw.oxy.edu. Please update your links and bookmarks.


The second law of thermodynamics and evolution 

 

Introduction

        Many fundamentalist Christians see the theory of evolution as a threat to their faith, evidently because it is not explicitly included in Genesis. (They also misunderstand the scientific application of the word "theory" that the chemist uses in discussing atomic theory or the kinetic molecular theory of gases, ideas as unquestioned by all chemists as evolution is by professional biologists.) This is tragic because it cuts off sincere individuals who are not scientists from understanding the powerful relevance of one of the most important concepts in all of science.

        Most disquieting to chemists who are interested in thermodynamics are the misleading statements about the second law and chemistry that creationist spokespeople have made. A few emphases from previous pages in the present Web site and from http://secondlaw.oxy.edu that bear on this unfortunate situation are developed below. At the end of this page are superior links to presentations of the second law of thermodynamics and its irrelevance to creationists’ arguments against evolution.

 

        "A watch must have required a watchmaker; a car could not have formed itself from parts."

        (The following includes some excerpts from the previous section, "Obstructions..")

        The above statements in italics from creationists are certainly true, but they have nothing to do with the behavior of atoms and molecules. Car parts in a junkyard don’t speed inside the yard at hundreds of miles an hour, constantly colliding with each other, fusing together to make a new transmission or a new car body so violently that enormous quantities of energy are given out!

        Why give a silly illustration like that? Anyone knows that it is not an inherent quality of metal parts to spontaneously join with similar or quite different parts to form complex new arrangements. Yet, this IS precisely the normal behavior of most of the chemical elements that constitute the world and the universe. The value of the second law of thermodynamics is that it quantitatively describes the energetic aspects of the chemical elements and the compounds they form. The chemical potential energy (the enthalpy of formation) that is bound in most of the 60,000,000 known kinds of molecules is less than that in their elements. Thus, energetically , the second law says that the majority of compounds now known could spontaneously form from the corresponding elements. In complete contrast, watches or cars are not lower in thermodynamic energy than the total energy of their individual components. Therefore, the second law says that it is totally inappropriate to compare them with the behavior of chemical compounds and elements.

        Incessantly moving at several hundred miles an hour at ordinary temperatures. hydrogen and many other atoms behave in a fashion that is impossible for car parts: Most atoms spontaneously "bond" when they vigorously collide, forming extremely powerful associations in very specific ways. These new arrangements can be molecules so stable that temperatures of thousands of degrees can't tear them apart again. Molecules are not atoms randomly stuffed in a package. When three or more atoms join to form a molecule, they are arranged in precise order, normally unchanging over time, and with a relatively fixed geometric relationship.

       Finally, many kinds of molecules can strike other kinds very violently and produce totally new types of molecules another mode of formation of new complex ordered structures due to the same innate nature of atoms to form strong bonds and spread out energy to the surroundings. Amino acids when simply melted with other amino acids (to make them move more rapidly) form huge new compounds. These are NOT useful or valuable proteins. The process simply illustrates the probability of the existence of complex gigantic substances in nature. Though not proteins, they are "proteinoid" in that they have hundreds to thousands of amino acid units firmly joined in the same kind of bonds that hold proteins together.

        A simple example of the spontaneous behavior of elements is the reaction of hydrogen gas with oxygen. Hydrogen atoms have such a great inherent tendency to form strong bonds with oxygen to yield water that a small energy of activation, in the form of a spark affecting only a relatively few molecules, causes the two substances to start to react, resulting in an enormous evolution of energy. This is exactly as the second law predicts: some of the energy in a mixture of hydrogen and oxygen becomes spread out (so much and so rapidly that it is an explosion) when the lesser energetic compound, water, is formed. Yet, water is more complex than the simple elements and its atoms are arranged in an exact geometric pattern.

        There are millions of compounds that have less energy in them than the elements of which they are composed. That sentence is a quiet bombshell. It means that the second law energetically FAVORS — yes, predicts firmly — the spontaneous formation of complex, geometrically ordered molecules from utterly simple atoms of elements. Popular statements such as "the second law says that all systems fundamentally tend toward disorder and randomness" are wrong when they refer to chemistry, and chemistry precisely deals with the structure and behavior of all types of matter.

To summarize this important conclusion that is known by very few who are not chemists: Energetically, the second law of thermodynamics favors the formation of the majority of all known complex and ordered chemical compounds directly from their simpler elements. Thus, contrary to popular opinion, the second law does not dictate the decrease of ordered structure by its predictions. It only demands a "spreading out" of energy when such ordered compounds are formed spontaneously.

Also, to repeat a caution: The foregoing only describes energetic relationships involving the second law. It does not mean that most complex substances can be readily synthesized just by mixing elements and treating them in some way. The second law has nothing to do with pathways or procedures of synthesis – only with energy and its tendency to spread out/disperse.

        Most complex molecules may require the expertise of one or of many chemists to put them together in a laboratory. However, so far as the second law of thermodynamics is concerned, not only water but cholesterol, DNA, the anti-depressant in St. John’s Wort and millions of other complex substances contain less energy than their constituent elements. Therefore, thermodynamically, their formation from those elements would be a spontaneous process, energetically favored by the second law.

 

"The Law of Disorder"

        As part of their attempts to challenge evolution, some religious writers have included comments to the effect that the second law – what they have called "the law of disorder" – strictly prohibits the chance formation of complicated structures from simple parts, including complex molecules from simple ones. This site, and especially http://secondlaw.oxy.edu, have shown repeatedly that it is fallacious to view the second law as a predictor of disorder. The second law concerns energy, not patterns of objects. The second law states that energy tends not to be restricted to one or a few energy levels in atoms and molecules, but to be dispersed to as many such levels as possible – rephrased in homely terms involving molecules, "Intense or concentrated energy tends to spread out and diffuse".

        In that spreading-out process, macro objects sometimes are displaced and moved to random arrangements that humans subjectively define as "disorder". A violent wind not only can break a window in a building and blow the papers in an office all over a square mile, but also destroy the building itself. However, this is an incidental consequence of dispersing and spreading out of the energy in a tornado, not an event that is due to the innate nature or behavior of inanimate objects themselves in the absence of such an energy flow. Moving common objects around so they fall in disorder is a singular and accidental aspect of the universal tendency of energy to diffuse, not the general thrust or meaning or requirement of the second law that applies to objects.

        Further, as described in the first section of this website, the second law is a tendency, not an instantly effected edict. Its predictions might not come true for millions or billions of years. These kinds of delay are due to the second law being obstructed and hindered by what chemists call "activation energies". All the biochemicals in our bodies except inorganic substances are protected and kept from oxidation or other disastrous reaction by activation energies. Almost all the materials from which our orderly prized artifacts are made are similarly kept from rapid oxidation in air. The second law is a powerful generality, but it is often blocked (to our human advantage) in chemical substances, chemical reactions, and physical events in everyday life.

 

"The second law says that complicated molecules can’t form spontaneously"

(This question is treated in greater detail and more technically in the last half of the previous section, "Obstructions to the second laws make life possible…")

        Of course, the most complex substances that we know are produced by organisms. The photosynthetic example often cited by creationists is as follows: Trees make sugars and cellulose as well as the green chlorophyll and other colored chemicals that we see in Fall leaves, among hundreds of other compounds. They use energy from sunlight by means of intricate chemical processes to synthesize the complex higher-energy content substances just mentioned from lesser energy compounds like carbon dioxide and water. But the second law says that the opposite process – of higher-energy compounds changing into lesser-energy substances – is what tends to happen by itself, spontaneously, without outside aid from any energy source. Therefore, photosynthesis is a thermodynamically non-spontaneous process.

        Religious writers are familiar with the general process of photosynthesis but are unskilled in dealing with chemical thermodynamics. They claim that the second law not only says that it is impossible for more complex substances to be spontaneously formed from simpler materials, but also a non-spontaneous process like photosynthesis that produces complex substances requires the presence of an organism, such as a plant.

        Neither claim is true. As has been discussed adequately in a previous portion of this essay about the second law and evolution, "A watch must have … a watchmaker", the spontaneous formation of millions of far more complex compounds than their elements is energetically favored by the second law. This is true whether the new molecule is more or less complicated than its starting materials because the second law is concerned only with energy. All other requirements or consequences are not within the purview of the law.

        It is equally erroneous to state that complex substances cannot be formed non-spontaneously from simpler without the intervention of an organism, "a patterning mechanism". Again, as has been discussed, the formation of patterned molecules is inherent in the nature of atoms combining with one another, no external template or help from a living organism is required by any physical law. "Non-spontaneous" simply means the addition of energy to a system of elements or compounds during the process of forming a new compound. Chlorophyll and substances as complex as chlorophyll have been synthesized in the laboratory, in glass vessels without the presence of any organisms in the reaction. Although that process was extremely difficult and took many person-years to complete, the principle was clear long before the chlorophyll project was undertaken: The non-spontaneous syntheses of greater-energy, complex substances from lesser-energy simple molecules without the aid of organisms is not prevented by the second law. It is just not favored. Over the past two centuries, millions of complex substances — admittedly less so than chlorophyll — have been made similarly in laboratory glassware without the need for organisms.

 

The spontaneous and non-spontaneous formation of complex compounds in space

        Finally, it should be recognized that both spontaneous and non-spontaneous reactions to form complex substances are common in outer space. The two most prevalent elements there are hydrogen and carbon with considerably smaller quantities of oxygen and nitrogen. Although relatively few atoms or molecules are present per cubic inch, in untold quadrillions of cubic miles of space there are many millions of tons of each.

        Organic compounds are those substances that contain carbon. (Because they differ so much from organic compounds in their properties, carbon monoxide, dioxide and the carbonates are not included.) The simplest organic compounds, called alkanes and composed only of carbon and hydrogen, contain portions or sections with one carbon atom holding two or three hydrogen atoms. Spectroscopic evidence for these characteristic alkane sections has been found throughout space. All alkanes are all lesser in energy than their elements. (Structures are in: http://www.nyu.edu/pages/mathmol/library/hydrocarbons/ ). Therefore, the second law says irrefutably that they could be formed spontaneously from carbon and hydrogen with the net evolution of energy. Their structural pattern is not vastly complex but it is far more so than that of individual elements.

        Even more complicated types of compounds that contain either carbon and hydrogen alone, or those elements with oxygen, have been detected in space: PAHs, polycyclic aromatic hydrocarbons. The thermodynamic category of formation of the two groups of PAHs are different. IF oxygen is present in the PAH ( and this cannot yet be decided spectroscopically ) the substances are less energetic than the carbon, hydrogen, and oxygen elements from which they were formed. Thus, they were formed spontaneously strictly in accord with the second law of thermodynamics.

It is an amusing sidenote that the anti-depressant ingredient in St. John’s Wort, listed as hypercin and the precise structure given in the Merck Index, is an oxygen-containing PAH. These are complex substances that are important here on earth. It is still questionable, of course, that molecules with this precise structure are in space, but it is energetically completely possible that it and many comparable materials may be present there.

PAHs composed only of carbon and hydrogen contain more energy within their molecules than do elemental carbon and hydrogen. Therefore, their synthesis from the elements is thermodynamically non-spontaneous. Nevertheless, these PAHs detected in space would have been formed "automatically", i.e., without any organismic intervention (!). Energy would have been supplied to the process, probably via powerful bursts of radiation from many kinds of stellar and similar sources.

        Even more convincing evidence of the existence of PAHs in space and in other parts of the universe is their presence in meteorites that have fallen to the earth. Extremely careful isolation of carbon-containing substances from some meteorites has proved the presence of specific polycyclic aromatic hydrocarbons.

        Cyanide compounds, formed from the elements of carbon and nitrogen, have been shown by spectroscopy to be prevalent in all comets, along with ice (spontaneously formed from hydrogen and oxygen). All cyanides are considerably higher in energy content than carbon and hydrogen and thus they must have been formed non-spontaneously thermodynamically.

        In summary, there is ample evidence for the existence of complicated, orderly molecules in outer space. They were formed without an organism’s assistance because no such organisms have been found associated with them in meteorites and, of course, none can thrive in the energetic conditions of outer space. The "automatic" formation of complicated, orderly substances both spontaneously and non-spontaneously is simply the consequence of normal chemical laws and the second law of thermodynamics. (The intense energy sources in space make possible non-spontaneous synthesis there.)

 

Links

        A superior list of links to scientific views of evolution as well as to the whole spectrum of creationist sites is in http://www.talkorigins.org/origins/other-links.html

        A scientific analysis of the problems creationists face in asserting that the second law is somehow an obstacle to evolution is http://www.talkorigins.org/faqs/thermo/probability.html

        A brief, but very substantive, response to creationists’ attributing false implications to thermodynamics is http://www.talkorigins.org/faqs/thermo/creationism.html

        A well-reasoned summary, "The Second Law of Thermodynamics in the Context of the Christian Faith" by a chemical physicist, who is also a devout Christian is in his Web page http://steamdoc.s5.com

For info from NASA on substances in space: http://www.astrochem.org

 

References

        Free energies of formation of chemical substances are most easily found in the CRC Press Handbook of Chemistry and Physics in Section 5 under "Standard Thermodynamic Properties ….". The ΔG values listed are for free energies of formation from the elements. Where ΔG values are missing and ΔH and S are printed, the ΔG can be calculated from the Gibbs equation, as shown in any general chemistry text.

Home

Back

Next page – "Entropy and Gibbs free energy, ΔG = ΔH – TΔS"