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Post: 36599723_1 created on Tue Jan 08, 2008 8:16 amPosted: Tue Jan 08, 2008 8:16 am
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Having hung out on Gaia and other many other message boards where evolution is discussed, I've noticed that one of the most frequent arguments that supposedly disproves evolution is bringing up the Second Law of Thermodynamics. However, doing so only reveals profound ignorance on the part of the people using such an argument.
The argument, as it is typically made, goes as follows: Ignorant Creationist The Second Law of thermodynamics says that everything tends to go from an ordered state, to a disordered state. Thus, there is no way that life (order) could have risen from a pre-biotic soup (disorder) or even increased in complexity (order) as it supposedly evolved. Similarly, the Big Bang must be wrong because it says that the universe started off in an explosion (disordered) and spontaneously formed galaxies (ordered). From this argument, we can see the (flawed) definition abused by creationists. In some cases, it works well enough. A fairly typical example given is that of someone's bedroom. If it begins in a clean (ordered) state, it is quite natural for it to get dirty (disordered). However, there are two problems with this definition that make the application of it to evolution completely incorrect. The first problem is that the Second Law requires what's known as a "closed system". What this means is that energy cannot be applied to the system you're looking at if you want to have the Second Law work. Using the example from before, this would mean that you can apply energy to your room through the means of doing work, to make your room clean again even if it gets dirty. In the case of Earth and life on it, the Earth is supplied by an enormous amount of heat from the Sun every day. Thus, the creationist argument falls apart right there. It fails because they dishonestly omit part of the requirements. However, there is an even more fundamental flaw with the argument as it is presented, that obfusticates even the part of the Second Law that they do use. To understand this, let's again look at an example. If we take a look at water at a molecular level, it's rather disordered. The arrangement of the molecules in regards to one another has no rhyme or reason. As I just noted, if you add energy to the system, using the creationist definition with that part actually added, this would indicate that we should see more "order". However, the exact opposite is the case. If energy is added (ie, heat) the water turns to gas and there is even less order. In the other case, if energy is removed from the system, it becomes ice which, on a molecular level, is a highly "ordered" crystalline structure. So what gives here? Either there is something wrong with the definition as creationists frequently use it, or someone owes me a Nobel Prize for disproving the single most well proven law in all of science. As much as I'd like a Nobel Prize and the money that goes along with it, you can probably guess that this isn't the case. In reality, the solution is that the definition of the Second Law as creationists frequently give is, pertaining to "order" and "disorder" is fatally flawed as well. In reality, the Second Law says absolutely nothing about either of these. What it does say something about, is "entropy". It states that, in a closed system, entropy will always increase for a non-reversable process. But this begs the question of, "What is entropy?" Many sources (even some textbooks) incorrectly define it as a measure of the disorder of a system. But as we have seen, this definition is too vague to be useful. What is useful, however, is the equation Boltzmann derived to quantify entropy. It's such an important equation, it's engraved on his tomb. The equation is: S = k * ln (W) In this, S is Entropy, k is the Boltzmann constant, and W is what's known as the multiplicity. For a more rigorous explanation of what multiplicity is, see the second post in this thread, but if you want to get the simplified version, it's essentially a measure of how probable a given state is in a given system. Let's take the distribution of air molecules in a room as an example for this. There's lots of ways to distribute the molecules. One way we could do it would be to shove all of them in one corner, leaving a vacuum in the rest of the room. However, there's very few ways of arranging the molecules to do this, thus it's not very probable. In other words, it has a low multiplicity (W) which in turn, means that would be a very low entropy state. However, if we distribute the air molecules evenly thoughout the room, there's lots of ways to do this with no real difference. You can take any molecule, move it anywhere else in the room, and it would still be extremely close to evenly distributed. Thus, it's easy to get to that state which means a high multiplicity and a high entropy. This corresponds to the everyday observation in which you have a pressurized gas in a container and open a valve, it expands into the surroundings. Of course this is not to say that entropy is the reason for this. The reason is because there is a higher pressure inside. Looking at multiplicity and entropy is just a way of being able to figure out which way it will go. But all in all, what is probable (ie, has a high multiplicity), is dependent on the forces in the system you're looking at. In the example of a pressurized vessel, that force is the internal pressure. Thus, the gas fills the room if there are no other (significant) forces acting on it. So what rules and forces govern the systems involved in evolution and the big bang universe? The latter is easier to explain so we'll start with that. The Big Bang states that the universe started in a hot, dense state which, for one reason or another, began to expand. Just after the Bang Bang, matter was pretty evenly distributed around the universe. From the previous example, you'd expect that this would already be a pretty high multiplicity state since we already said that evenly distributing gas in a room was the best you could do. But you'll also recall that I had a caveat: There must not be any other (significant) forces acting on it. But in the universe, there is an immensely important force: Gravity! As we should all well know, gravity likes to pull things together. Thus, instead of an even distribution being the most probable, the presence of gravity makes clumping the more probable situation. Thus, there is no problem with the Big Bang violating the second law. You may be noticing a bit of a disparity at this point though. Gravity doesn't just exist in the universe at large and not in our rooms, so why do we get to allow gravity to change what's probable in the universe, but not our rooms? The reason is that other caveat I had: it must be a significant force. In our rooms, the forces of the particles banging against each other through random thermal motions is several orders of magnitudes higher than the effects caused by gravity. Thus, it's not terribly significant. The same would be true in the universe right after the Big Bang. Random thermal motions would have prevented collapse for some time. The difference is that because the universe is expanding, the amount of energy in a given square meter is also decreasing. Thus, there becomes a point where gravity does become significant. The same is not true for your room. It is not expanding, and thus, gravity remains insignificant. But what about evolution? Again, we must take a look at what forces and rules are at work in this system. One rule that goes unstated pretty often, possibly because it should be so self evident, is that things that last longer tend to be more frequent. For example, there are lots of isotopes of iron around. The most common is Iron 56. Less common is Iron 60. Iron 56 is a stable atom whereas Iron 60 has a half life of a few thousand years. Since Iron 56 lasts longer, it's no wonder we see more of it around! While there are lots of different ways we could have the ratio of these two elements, this rule pushes it towards what it should be. If there were, at one point, lots of Iron 60, this would be the low multiplicity/entropy state, and it would go back towards the state where there's more Iron 56. The rule, as pointed out by entropy, pushes the system in a certain direction. If we extend this to larger molecules, the rule still applies. Molecules that are stable and strong survive and are more prevalent, whereas ones that are flimsy aren't as common. If you're familiar with Darwin's theory of evolution, you should already see where this is going. The statement I'm making is applying the common sense rule to non-organic matter. Darwin just took it one step further and applied it to life itself; Life that does better, tends to be more prevalent. Of course, that doesn't describe the entirety of evolution. There's another component that's missing: Change. The difference between Iron and life is that, unlike life, Iron doesn't self replicate. Life does. And when it does, it makes mistakes. This is known as random mutation. Thus, the resultant organism won't necessarily be the same as the previous one. Since there is a difference, the rule we discussed earlier, in which adapted organisms become more prevalent, then takes over to carry on throughout the generations. These two rules, random mutation + natural selection, are the basis for the system and determine what will be most probable; The most well adapted organisms will be. Thus, since evolution predicts what is most probable, there is no discrepancy with the second law. In this case, the Second Law, when analyzed with the proper understanding of what is probable, actually predicts that we should see an increase in complexity because the rules dictate it. However, without even going that far, we can still demonstrate how incorrect the creationist argument is simply by looking at a qualitative analysis of what happens in the process of evolution as it pertains to the second law. Instead of writing all of this again myself, I'll copy/paste from this post at Pharyngula: PZ Myers It's a very bad argument they are making, but let's consider just the last sentence of the quote above. Henry Morris This represents in absolutely gigantic increase in order and complexity, and is clearly out of place altogether in the context of the Second Law. Daniel Styer has published an eminently useful article on "Entropy and Evolution" that does exactly that — he makes some quantitative estimates of how much entropy might be decreased by the process of evolution. I knew we kept physicists around for something; they are so useful for filling in the tricky details. The article nicely summarizes the general problems with the creationist claim. They confuse the metaphor of 'disorder' for the actual phenomenon of entropy; they seem to have an absolutist notion that the second law prohibits all decreases in entropy; and they generally lack any quantitative notion of how entropy actually works. The cool part of this particular article, though, is that he makes an estimate of exactly how much entropy is decreased by the process of evolution. First he estimates, very generously, how much entropy is decreased per individual. If we assume each individual is 1000 times "more improbable" than its ancestor one century ago, that is, that we are specified a thousand times more precisely than our great-grandparents (obviously a ludicrously high over-estimate, but he's trying to give every advantage to the creationists here), then we can describe the reduction in the number of microstates in the modern organism as: Fig 1. Now I'm strolling into dangerous ground for us poor biologists, since this is a mathematical argument, but really, this is simple enough for me to understand. We know the statistical definition of entropy: Fig 2. In the formula above, k_B is the Boltzmann constant. We can just plug in our estimated (grossly overestimated!) value for Ω, have fun with a little algebra, and presto, a measure of the change in entropy per individual per century emerges. Fig 3. Centuries are awkward units, so Styer converts that to something more conventional: the entropy change per second is -3.02 x 10^-30 J/K. There are, of course, a lot of individual organisms on the planet, so that number needs to be multiplied by the total number of evolving organism, which, again, we charitably overestimate at 10^32, most of which are prokaryotes, of course. The final result is a number that tells us the total change in entropy of the planet caused by evolution each second: -302 J/K What does that number mean? We need a context. Styer also estimates the Earth's total entropy throughput per second, that is, the total flux involved from absorption of the sun's energy and re-radiation of heat out into space. It's a slightly bigger number: 420 x 10^12 J/K To spell it out, there's about a trillion times more entropy flux available than is required for evolution. The degree by which earth's entropy is reduced by the action of evolutionary processes is miniscule relative to the amount that the entropy of the cosmic microwave background is increased. As such, the Second Law is frequently abused by creationists. However, their strawman version has two flaws: Lack of intelligent and meaningful terminology, as well as dishonest disregard of important parts of the Second Law. Neither Evolution nor the Big Bang are contradicted by it since the rules and forces acting within the respective systems dictate what is most probable and this conforms to the predictions made by the Second Law. Further reading: Evidence & Testing in the Scientific Field The Failure of Irreducible Complexity Is Intelligent Design Different that Creationism? Why are ID Proponents/Creationists intellectually dishonest? Evolution - What it is and isn’t Evolution and its Compatibility with Creationism Expelled: No Intelligence Allowed (An ID Propaganda Film) Updates - 4/15/08 - Added link to Expelled: No Intelligence Allowed (An ID Propaganda Film). - 11/11/08 - Added quantitative section from Pharyngula. |
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