The Second Law of Thermodynamics Does Not Prohibit Evolution

The Second Law of Thermodynamics Let me restate the statement of the Second Law I made in the definitions. “. .. if the physical process is irreversible, the combined entropy of the system and the environment must increase. ”[1] Now, entropy to fundamental to an understanding of the Second Law. Mathematically, the definition of entropy is that a change in entropy equals the integral of dQ/T, where dQ is an infinitesimal change in heat and T is the temperature. The integral is definite, running over two temperatures. Another mathematical definition is that S=k*ln(w), where S is the entropy, k is Boltzmann's constant, and w is the multiplicity of a system. Both definitions are helpful to understanding entropy in the current context. The first definition says that the flow of heat changes the entropy of a system. It follows from the definition of temperature itself. Now, one doesn't have to use the Second Law to deduce that heat always spontaneously flows from hot objects to cold objects. The entropy being created in the cold object as the heat flows into it is always greater than the entropy lost in the hot object, because the dependence is 1/T. This, in itself, is one form of the Second Law. [2] The second definition says that the entropy of a system is proportional to its multiplicity. The multiplicity is the number of microstates in one macrostate. One does not need to know the combinatorics behind this. View the multiplicity as simply a measure of the number of states of the system. The basic point is, hotter, bigger, less pressurized systems have a larger multiplicity, or more potential states than colder, smaller, more pressurized systems. This is another form of the Second Law. It is less important in the current context, but I mentioned it because it isn't a statement about the change in entropy, but in the entropy itself, and because it helps to conceptualize entropy. [3] The definition of a irreversible process seems obvious enough. The second law says that, in the case of an irreversible process, the combined entropy of the system and the environment must increase. Spontaneous heat flow is an example of an irreversible process, so this agrees with what followed from the first definition of entropy. Now, it is important to note that the Second Law only applies to an isolated system (one where the system does not interact with anything outside it). Every real physical system interacts with its environment. So, you can have the entropy of the system itself decrease by giving the system energy. But even if it is an isolated system, local areas can still have decreasing entropy, but only if the entropy of the environment increases by at least as much as that decrease. Taking into account the system and all its effects on the environment would constitute an isolated system. In general, for this debate, we can view the Universe as the environment. Finally, the relation between entropy and order needs to be addressed. It is often claimed that entropy is disorder. However, this is not true. “Entropy is not disorder, not a measure of chaos, not a driving force. Energy's diffusion or dispersal to more microstates is the driving force in chemistry. Entropy is the measure or index of that dispersal. .. From a molecular viewpoint all such entropy increases involve the dispersal of energy over a greater number, or a more readily accessible set, of microstates. This confusion about disorder and entropy comes from 1895 before an adequate understanding of the details of energy change in atoms and molecules was possible. ” In other words, it is entirely possible for a disordered state to become ordered even as the state's entropy increases. [4] Summarizing all this together, the Second Law only argues that non-equilibrium states will tend to shift towards becoming equilibrium states. Anisotropies should, given enough time, become isotropies. “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. ” In sum, a process is not prohibited simply because the resultant state is more ordered than the initial state. [5] Evolution and the Second Law of Thermodynamics Taking the Universe as the environment, the only important bodies are the Earth and the Sun. The Earth receives energy from the Sun in the form of sunlight. This means that the Earth itself is not a closed system. The sunlight contains energy, some of which is dissipated to the Earth, and the rest is reflected back into space, having less energy, and therefore more entropy than what it had originally. So, this process increases the energy of the Earth, and this can power local decreases in entropy on the Earth. From all that has already been discussed, we can draw two conclusions. One, entropy has very little to do with order or disorder. And two, entropy can decrease, either by having an energy input or by a “redistribution” of currently existing entropy. This means that there can be areas on the Earth where order can arise from disorder. So, even if we accept that evolution is a process that creates order from disorder, it is entirely possible. However, not even that much has to be conceded. It turns out that the processes of evolution arise from commonly occurring scientific processes. “The only processes necessary for evolution to occur are reproduction, heritable variation, and selection. All of these are seen to happen all the time, so, obviously, no physical laws are preventing them. In fact, connections between evolution and entropy have been studied in depth, and never to the detriment of evolution. ”[6] But it goes further than this. Not only are the processes necessary to evolution fully compatible with the Second Law, modeling the environment can actually predict how evolution will occur. Take Cope's rule, the rule that, over time, species tend to increase in body size. This increases the overall entropy of individuals over time. One study modeled this, and found, “Most mammals can be considered as evolving under ecological conditions which induce slow or stationary population growth; hence, this pattern of entropy increase accords with our predictions. ”[7] Among other things, “Several scientists have proposed that evolution and the origin of life is driven by entropy. Some see the information content of organisms subject to diversification according to the second law, so organisms diversify to fill empty niches much as a gas expands to fill an empty container. Others propose that highly ordered complex systems emerge and evolve to dissipate energy (and increase overall entropy) more efficiently. ”[6] The study mentioned two paragraphs above concluded that, “These observations indicate that the increase in evolutionary entropy under bounded growth constraints have both strong explanatory and predictive properties and constitute a unifying principle for understanding the patterns generated by mutation and natural selection over evolutionary time. ” This means that, not only can the Second Law allow for evolution, it encourages it. Conclusion Entropy is not necessarily correlated with disorder, meaning that the order of a system can increase even as its entropy increases as well. The Earth is not an isolated system, meaning that energy coming from the sun can power entropy decreases. Both of these imply that the Earth can experience increases in order. Not only does this allow for evolution, but evolution itself is compatible with evolutionary models. Overall, the second law of thermodynamics does not prohibit evolution. Sources[1]: . https://www.grc.nasa.gov...[2]: . http://en.wikipedia.org...[3]: . http://people.brandeis.edu...[4]: . http://www2.ucdsb.on.ca...[5]: . http://2ndlaw.oxy.edu...[6]: . http://www.talkorigins.org...[7]: . http://www.philbio.org...