From: Allan Angus
Subject: Entropy article in your July 20th issue
Date: September 2, 2012 12:27:47 AM CDT
To: Brad Dye Brad, Back in your July 20th issue , you published an article about entropy that, on its own merits, was a fairly innocuous bit of work. It simply reproduced much of what a first year engineering or science student might have picked up about entropy. However, what stuck with me was your opening statement, which I quote, “Creationists believe that the second law of thermodynamics does not permit order to arise from disorder, and therefore the macro evolution of complex living things from single-celled ancestors could not have occurred.” I certainly believe that the second law of thermodynamics does allow order to arise in our universe, and demonstrably so. For some time, I had decided against responding, since the idea that I'd be able to communicate anything like the complexity of the modern scientific view of this problem in a short “letter to the editor” seemed rather implausible. However, nothing ventured, nothing gained, as they say; and so, once more into the fray... To the extent that the example in the article shows the “mixing” behavior expected of particles of typical atomic sizes at some temperature in some container and, by and large, constrained primarily by electromagnetic forces and the Pauli exclusion principle, all is well. In fact, almost all example presented in the curricula of undergraduate classes in engineering and science focus on the behavior of systems in which the dominant forces present are electromagnetic. These forces display themselves in the collisions between particles, between particles and containers or pistons, in applied electromagnetic fields, and so on. To the extent that gravity is mentioned, it appears as some form of potential field that can yield an exponential distribution of particles due to their mass; e.g., the distribution of gases in the earth's atmosphere. It is a rare undergraduate course that introduces the work of men like Ilya Prigogine, who won the Nobel Prize for his work on dissipative structures in thermodynamic systems far from equilibrium. (See http://en.wikipedia.org/wiki/Ilya_Prigogine ) Such structures are able to reverse the flow of entropy and to yield, as the modern statement goes, produce order out of chaos. Oddly enough, in Latin as “ ordo ab chao ” this is a motto of Craft Freemasonry. It is also a central component of the work of Stuart Kauffman. Your readers may find his paper on “Approaches to the Origin of Life on the Earth” of some interest in this regard ( http://www.mdpi.com/2075-1729/1/1/34 ). They might also find Kauffman's essay for Edge equally enlightening: http://www.edge.org/3rd_culture/kauffman06/kauffman06_index.html I introduce Prigogine and Kauffman simply to introduce your interested readers to the knowledge that it is non-equilibrium and non-linear thermodynamics from which modern science proposes that the early rudimentary forms of life arose. In any case, back to the diagram in your article. Again, it will be familiar to anyone with a background in engineering or science. However, it is a paradigmatic case for the relatively short-range scale associated with the electromagnetic force. The situation with respect to gravity is virtually the opposite picture. Imagine instead that the diagram is showing galaxies on some significant scale within our universe. The evolution is completely reversed as gravity causes increased “clumping” towards the centers of mass that first form stars, then galaxies, then galactic clusters, and along the way, black holes. As Steven Hawking has shown, a black hole has the maximum entropy for any object with the size of its event horizon. See http://en.wikipedia.org/wiki/Black_hole_thermodynamics for example. In this way, the evolution of our universe from the Big Bang is a combination of factors on different scales; and the action of entropy and the arrow of time is quite distinct on these scales. For example, consideration of the Cosmic Microwave Background Radiation (CMBR) from WMAP shows an extremely uniform temperature at 2.725K. (See http://en.wikipedia.org/wiki/CMBR ). This is a remnant of the temperature of the universe at around 379,000 years after the Big Bang. However, there are fluctuations in the CMBR at around ±18µK, and these fluctuations are demonstrated in features that are around 300,000 light-years across. These factors have been taken as evidence for an inflationary period during the early stages of the universe in which thermodynamic equilibrium had been achieved, and then broken, freezing in these fluctuations. This suggests that the early state of the universe was one of high entropy relative to the dominant force at the time; viz., the electromagnetic force. However, the fluctuations in energy density shown in the CMBR represent the points towards which gravitation would subsequently act in the maximization of entropy via the production of black holes. It is this sort of interplay that could have given rise to life on earth, and on similar planets. The early Big Bang produced only hydrogen, helium and lithium atoms. The abundance of these elements in interstellar space is consistent with our current view of the production of these light elements to a high degree of accuracy. Heavier elements, essential for life, would have to have been produced within first generation stars; and then distributed after they went nova. The action of gravitation would then pull these elements back together into new stars and planetary systems. Current estimates of the time it would take to create heavier elements in the relative densities that we find in our solar system is around 10 billion years. Given that we now have an estimate on the age of the universe at 13.7 billion years, and an estimate of the age of the planet at around 4.5 billion years, everything appears to come together nicely, thank you very much. It is sometimes suggested that the dominant role that our sun plays as far as life on the planet is concerned is to provide energy. This is not completely true. The net energy that the sun delivers is actually, and has to be, zero. The energy that is absorbed by the earth as photons from the sun in the day is delivered back to the sky, again as photons. The difference is that the temperature of the sun, as a bright point in a dark sky, makes its average photon quite energetic, in thermal equilibrium at about 5700K. In order to maintain an energy balance, the earth has to radiate many more lower energy photons at night, since the earth's temperature is more like 270K. The important difference is the lower entropy of the inbound flow of photons versus the higher entropy of the outbound flow. Life on earth depends upon this entropy exchange, as Prigogine and Kauffman have pointed out. The essence of the situation is the fact that the planet is in a situation well away from thermal equilibrium, and precisely in the conditions necessary for the creation of dissipative systems that can reverse the typical flow of entropy in short scale, electromagnetic systems. We are balanced between the reverse behaviors of entropy maximization in large-scale gravitation and small-scale electromagnetics. The point here is that it is the entropy flow from lower to higher, and not the energy flow that is essential. If the earth were uniformly heated by some overall background at exactly 270K, then life would not evolve or have support. That is, if the planet were in thermal equilibrium in some huge “easy bake oven” then the flow of photons in would be in detailed balance with those going out. There's an equilibrium as far as energy is concerned and the temperature would be identical, in exactly the same way as in the real case; but the situation with respect to entropy flow would be extremely different. In thermal equilibrium, life doesn't work. The reason that the sun is a bright point in a dark sky is gravitational clumping. It, and our solar system, are apparently on their way to being a black hole at some time in the distant future. Along the way, we happen to have come along, become conscious of this marvel, and commented upon it. For those of your readers with some background in science or engineering then, our living planet earth can be seen as a kind of Carnot heat engine. It takes in heat at 5700K from the sun and exhausts it to the dark sky at 2.7K. In between, the work it does is our lives. There are many more marvels in the physics of the Big Bang. Unfortunately, they really are too technical and abstract to describe here. I would like to draw one analogy though. In the middle ages, and in spite of some Ionian Greek philosophers having made good estimates of the radius of the earth and the fact that it rotated around the sun, most Europeans held with church dogma that the earth was flat and that the sun moved around it. As a consequence, there was a view that travel far out into the ocean would lead one to fall off the edge. In a very similar way, the entire universe, including the fabric of space and time, are curved near the Big Bang event. There are many aspects to this situation. There are no particles with mass, and mass is essential for the creation of clocks and the measurement of time. The universe is extremely uniform, and entropy flow is essential for time. Energy density is extremely high, and so all dimensions are warped. And so on. With this rather vague conclusion, I must let my letter to the editor stand. If readers go away with only one picture, let it be that your diagram of the natural flow of entropy applies only to conditions of one force on one scale; for gravitation on the broad scale of the universe, the flow is reversed. It is just this balance, on a planet near a bright point in the dark sky, caused by gravitational clumping, that electromagnetic systems can feed off the negative entropy from the sun and live. —Allan adangus@me.com |
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