Sunday, January 3, 2010

Answering Creationist Claims (Part 7 – The 2nd Law of Thermodynamics Truthfully Explained)

One of the most common creationist claims is that evolution is in conflict with the 2nd Law of Thermodynamics – and yet it is one of the most thoroughly refuted claim. Yet ignorance is still widespread about this claim, and I will give a thorough explanation on this law.

Definition of Thermodynamics

Thermodynamics is study of the laws that govern:

  • the conversion of energy from one form to another;
  • the direction in which heat flows;
  • and the availability of energy to do work.

Thermodynamics is based on the concept that there is a measurable quantity of energy in any closed system, known as the in the internal energy (U). This only takes into account the total kinetic and potential energy in the matter of the system that can be transferred as heat, and thus doesn’t involve chemical and nuclear energy.

The 2nd Law of Thermodynamics Explained

The 1st Law of Thermodynamics states that energy in an isolated system must be constant. Thus, for the the internal energy (U) of the system to change, it must be open. In a system of constant mass, the internal energy is equal to the heat present (Q) plus the amount of work done (W). Hence the equation: U = Q + W.

This is exactly the same as the principle of the conservation of energy, which states that energy can only be converted, but never created or destroyed. All natural processes strictly conform to this law, and this brings us to the 2nd Law.

While energy can transform from one form to another, in all cases, the process is irreversible to a certain extent. The direction of flow of energy and the principle of entropy is the subject of the 2nd Law of thermodynamics.

Rudolf Clausius, founder of the concept of entropy, stated that:

heat cannot be transferred from body to a second body at a higher temperature without producing some other effect


the entropy of a closed system increases with time

These 2 statements gave rise to the concept of temperature (T) and entropy (S). Temperature determines whether heat will flow into or out from the system; entropy is the measure of the unavailability of energy in a system to do work.

Lord Kelvin explains the Law further:

It is impossible to convert heat completely into work in a cyclic process.

What can we infer from their statements? Firstly, heat will tend towards flowing from a system of higher temperature to one of lower temperature. And when this process occurs, usable energy is irreversibly lost, and thus the overall entropy of the system increases. For the entropy of one system to decrease (aka increase of usable energy), energy must be transferred from a second system of higher temperature, and at cost of increased entropy of the second system. Based on this Law, Lord Kelvin put forward the idea of the “Heat Death of the Universe” as a possible way in which the Universe may come to an end.

In short, the definition for the 2nd Law of Thermodynamics is: the law that states the direction of heat flow and dictates that overall entropy in a closed environment increases over time.

Carnot's Heat

Carnot's Heat Engine diagram (modern) - where heat flows from a high temperature TH furnace through the fluid of the "working body" (working substance) and into the cold sink TC, thus forcing the working substance to do mechanical work W on the surroundings, via cycles of contractions and expansions.

The Sun as the One and Only Source of Energy

Creationists claim that the Second Law of Thermodynamics is true, and thus evolution cannot occur. This claim however, is based on a misunderstanding of the Law. Let’s take a look at Bible Life Ministries version of the claim:

The second law of thermodynamics proves that organization cannot flow from chaos. Complex live organisms cannot rearrange themselves into an organism of a higher form as claimed by evolutionists. This is scientifically backwards according to the second law of thermodynamics, which has never been proven wrong. Scientists cannot have it both ways. The second law of thermodynamics is proven to be correct. Evolution lacks any scientific proof. The Theory of Evolution is contrary to proven scientific truth.

The problem with their claim is that the 2nd Law of Thermodynamics works only with in closed system, and the Earth (or more specifically, the Earth’s surface) is not isolated. Meet the Sun.

The Sun, a massive ball of hydrogen plus helium is constantly undergoing nuclear fusion, a process that gives out massive amounts of energy to the Solar System. This is can only be expected as heat always flow from a place of higher temperature to one of lower temperature, as stated in the 2nd Law. Because of this, the Earth’s entropy is maintained, and thus is able to support evolution, and life itself for that matter. Without a source of energy, both creationism and evolution is not possible, as life would never have appeared. Of course, maintaining the Earth’s entropy requires an increase in the Sun’s entropy.

Another point is that evolution would still be possible even if the entropy of the Earth’s surface is increasing (given that it is slow enough). The mechanisms of evolution is largely based on genetic mutations + natural selection. Genetic mutations will surely occur, regardless of entropy levels. An increase in usable heat/energy will not prevent mutations. Natural selection is also quite unrelated to the Laws of Thermodynamics. It is simply the process in which individuals which are better adapted to the environment and are fertile get to to pass their genes on. These processes aren’t directly related to thermodynamics (see Definition of Thermodynamics). If I am wrong on this, please tell me :-). Thanks.


In this post, I have given the truthful explanation of the 2nd Law of Thermodynamics. Thermodynamics is shown to be unrelated to the processes that drive evolution, but even if it did, evolution would be possible, as the Sun is still there. So no, creationists, stop using that refuted-a-thousand-times tactic.

The next post will address Bible Life Ministries claim that the chromosome count is unchangeable, and that species are “fixed”. Stay tuned.


(2005). Oxford Dictionary of Science Fifth Edition. Oxford University Press Inc. pp 812-813. ISBN 978-0-19-280641-3

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Next: Answering Creationist Claims (Part 8 - The Fluid Nature of Chromosomal Count)