Second law of thermodynamics
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| “ | Nothing in life is certain except death, taxes and the second law of thermodynamics. | ” |
| —Seth Lloyd | ||
The second law of thermodynamics states that "the entropy of an isolated system does not decrease". This is often taken to mean that "disorder always increases" and is frequently misinterpreted.
Contents |
[edit] Explanation of terms
[edit] Thermodynamic systems
- Open system - Exchanges both matter and energy with its surroundings
- Closed system - Exchanges energy, but not matter, with its surroundings
- Isolated system - Exchanges neither energy nor matter with its surroundings
The universe is an isolated system since it is a term to describe the entire space-time continuum, including all of the energy stored in it. In reality, the universe is regarded as the only true isolated system, as perfect isolation on a smaller scale is impossible. The Earth can be viewed as approximately a closed system, although it is open in reality.
[edit] Entropy
Strictly speaking, entropy is the logarithm of the multiplicity of states, or the degree of dispersion of energy in a system.
A more commonly given definition is "degree of disorder in the system," and hence the Second Law of Thermodynamics is often explained as "systems become increasingly disordered." From the definition above, this is equivalent to saying that a system will tend to transition from less probable to more probable sets of states. For example, given any five playing cards, one is far less likely to have a something "ordered", like a winning poker hand, than a disordered, seemingly random hand. So even though all hands are equally likely, one subset of hands may be more likely than another.
Actually entropy is a little more abstract and the second law of thermodynamics implies that the universe will always become increasingly uniform; that is, heat will spread until the entire universe has the same temperature and energy level (in a closed system heat will always spread from a place where there is a lot of heat to a place where there is less until balance is achieved), and forces will continue to work until a universal balance has been achieved.
The physical analogy usually given is that a room will over time becomes more disordered (stuff gets distributed evenly throughout the room instead of being concentrated in a neat stack) as long as a person lives in it but does no effort to clean it out. In the physical world, all energy is converted to heat, and becomes more uniformly distributed among the universe, until the universe becomes energetically uniform. In its final state the universe will become one uniform space where no work can be done since energy cannot be "concentrated" by doing work. This state is called maximum entropy. When the universe has reached this state it is said to be completely disordered as there are no ordered patterns left and there is no way to ascertain information about the history of the universe.
Scientific educators have recognized that the disorder terminology, while simple, is an oversimplification at best, and a false analogy at worst, and most chemistry textbooks have removed (or at least heavily edited out) the disorder terminology. [1] Of utmost importance, entropy is an energetic phenomenon, and only tangentially has to do with the distribution of matter in a system.[2] (Statistically speaking, the molecules of a gas are unlikely to move to one side of a container without work being done on the gas. But this would increase the entropy of the universe, as the plunger, or whatever does the compression, would have to increase its entropy.)
[edit] Misapplication by anti-evolutionists
The false analogy of entropy as disorder is used in a number of fields outside of science with varying success. Creationists have picked up on disorder terminology and attempted to apply the second law of thermodynamics as a refutation of evolution. The analogy would state that more complex life-forms could never evolve from simpler ones.
This false analogy of a false analogy is incorrect. First, evolution does not imply that life is becoming increasingly complex; it only says that natural selection allows genes to be passed on and different characteristics hence preserved.
It also is a corruption to believe life is always "more ordered" than inanimate objects. In fact, life does not violate the second law of thermodynamics in strict energetic sense. The energy of the sun is converted into chemical potential energy, which is converted to mechanical work or heat (the Earth is not an isolated system.) In each case, the energy transfer is inefficient, and some energy is dissipated as heat to the environment, leading to a dispersion of energy. (In the same way, "ordered" snowflakes can form when the weather becomes cold but the entropy of the universe still increases.)
As PZ Myers put it: "The second law of thermodynamics argument is one of the hoariest, silliest claims in the creationist collection. It's self-refuting. Point to the creationist: ask whether he was a baby once. Has he grown? Has he become larger and more complex? Isn't he standing there in violation of the second law himself? Demand that he immediately regress to a slimy puddle of mingled menses and semen."
Furthermore, Carl Sagan points out that if the second law of thermodynamics were applied to a god, then god would necessarily have to die.[3]
(Also, ask them what the zeroth, first, and third laws of thermodynamics are. See if they know.)
(See also, The Simpsons: "Lisa! In this house we obey the laws of thermodynamics!")
Some young Earth creationists have invoked "hydrodynamic sorting" in Noah's flood to account for the organization of the fossil record. Thereby they implicitly acknowledge that an undirected mechanical process is capable of producing order from disorder, and contradict their naive version of the second law of thermodynamics.
[edit] See also
[edit] External links
- The Second Law of Thermodynamics by Frank L. Lambert, Professor Emeritus of Occidental College
[edit] Sources
- Physics for Scientists & Engineers (6th edition) Raymond A. Serway & John W. Jewett, Jr.
[edit] Footnotes
- ↑ http://www.entropysite.com/ (retrieved 12 February 2009)
- ↑ When confining matter to a smaller volume, there are less translational energy levels available to the system and hence a lower density of states for a system. It is the number of microstates of the energy quanta that is important in determining the entropy of the system, and hence the two are related.
- ↑ The God Hypothesis atheistnexus.org
