A Choice of Catastrophes Read online

  Again, suppose that the movie showed us water flowing from the nearly empty container into the full container. We would be quite certain that the film was running backward. In the movie universe, the direction of time-flow was the reverse of what it is in real life. (In fact, the effect of running a movie film backward is almost invariably humorous because there are innumerable events that then happen that we know never happen in real life. Splashing water draws itself inward while a diver heaves out of the water feet-first and lands on a diving board; the fractured shards of a glass draw themselves together and fit themselves perfectly into an intact object; wind-blown hair is wafted into a perfect coiffure. Watching any of this makes us realize how many events in real life are clearly spontaneous; how many reversals, if they actually took place, would seem clearly miraculous; and how well we know one from the other simply through experience.)

  Returning to the two containers of water, it is easy to show that the rate at which the water flows from the full container to the nearly empty one depends on the difference in the energy distribution. At the start, the potential energy of the water in the full container is considerably greater than the potential energy of the water in the nearly empty one, so the water flows quickly.

  As the water level drops in the full container and rises in the empty one, the difference in potential energy between the two containers decreases steadily, so that the distribution of energy is less uneven, and the water flows at a steadily decreasing rate. By the time the levels of water are almost even, the water is flowing at a very slow rate and when the levels of water in the two containers are quite even, and there is no potential energy difference at all between them, the water flow stops altogether.

  In short, the spontaneous change is from a state of uneven distribution of energy to a state of even distribution of energy, and at a rate that is proportional to the amount of unevenness. Once the even distribution of energy is achieved, change stops.

  If we were to watch two connected containers of water, with the water level equal in both, and with no intervention from the outside at all, then if water flowed in either direction so that the level in one rose and the level in the other dropped, we would be witnessing a miracle.

  The moving water can do work. It can turn a turbine which will generate a flow of electricity, or it can simply push things along with it. As the rate of water flow slows, the rate at which work can be done slows with it. When the water flow stops altogether, no further work can be done.

  When the water flow stops, when the height of water is the same in both containers, then everything stops. Ail the water is still there. All the energy is still there. All that water and energy, however, is no longer unevenly distributed. It is the uneven distribution of energy that produces change, motion, work, as it strives towards even distribution. Once the even distribution is achieved, there is, thereafter, no change, no motion, no work.

  Furthermore, the spontaneous change is always from uneven distribution to even distribution, and once the even distribution is reached, nothing spontaneous will ever change it back to an uneven distribution.6

  Let’s take another example; one that involves heat rather than water level. Of two bodies, one may contain a higher intensity of heat energy than the other. The level of intensity of heat energy is measured as ‘temperature’. The higher the level of intensity of heat energy of a body, the higher its temperature and the hotter it is. We can therefore speak of a hot body and a cold body and find them equivalent to our earlier case of the full container and the nearly empty container.

  Suppose that the two bodies formed a closed system so that no heat could flow into them from the outside universe and no heat could flow out of them into the outside universe. Now imagine the two bodies, the hot one and the cold one, brought into contact.

  We know exactly what would happen from our experience with real life. Heat will flow from the hot body into the cold body, just as water will flow from a full container into an empty one. As the flow of heat continues, the hot body will cool down and the cold body will warm up, just as the full container grew less full and the empty container grew fuller. Finally, the two bodies will be at the same temperature, just as the two containers ended with the same water level.

  Again, the rate of heat flow from the hot body to the cold body depends on the amount of uneveness of energy distribution. The greater the difference in temperature between the two bodies the more rapidly heat will flow from the hot body to the cold one. As the hot body cools and the cold body warms, the temperature difference decreases and so does the rate of flow of heat. Finally, when the two bodies are at the same temperature, the flow of heat stops altogether and moves in neither direction.

  Again, this direction of heat flow is spontaneous. If two bodies of different temperatures were brought together and if heat did not flow, or if heat flowed from the cold body into the hot body so that the cold body grew still colder and the hot body still hotter—and if we were sure we were dealing with a really closed system and there was no hanky-panky—then we would have to conclude we were witnessing a miracle. (And again no such miracle has been witnessed and recorded by scientists.)

  Then, too, once the two bodies are at the same temperature, any heat flow that would cause either of the two bodies to grow warmer or cooler does not take place.

  Such changes are once again related to the flow of time. If we took a movie of the two objects, focusing on a thermometer attached to each, and noticed that one temperature remained high and one low, with no change, we would conclude that the film was not moving. If we notice that the mercury thread in the thermometer at the higher temperature rose higher still, while the mercury thread in the other thermometer dropped lower still, we would conclude that the film was being run backward.

  Making use of a hot body and a cold body, we could arrange to have the heat flow do work. Heat from the hot body could evaporate a liquid and the expanding vapour could push a piston. The vapour could then deliver its heat to the cold body, become liquid again, and the process could continue over and over.

  As the work is done and heat flows, the hot body transfers its heat to the evaporating liquid and the vapour, as it condenses, transfers its heat to the cold body. The hot body therefore grows cooler and the cold body gets warmer. As the temperatures approach each other, the rate of heat flow decreases and so does the amount of work done. When the two bodies are at the same temperature, there is then no heat flow and no work is done at all. The bodies are still there, all the heat energy is still there, but there is no longer an uneven distribution of the heat, and therefore no longer any change, any motion, any work.

  Once, again, the spontaneous change is from uneven distribution of energy to even distribution, from the capacity for change, motion and work, to the absence of such capacity. Again, once such capacity disappears, it does not reappear.

  THE SECOND LAW OF THERMODYNAMICS

  Studies on energy usually involve a careful consideration of heat flow and of temperature change because this is the easiest aspect of the subject to handle in the laboratory—and because it was also particularly important at a time when steam engines were the major method of turning energy into work. For this reason the science of energy-change, energy-flow, and the conversion of energy into work was termed ‘thermodynamics’ from Greek words meaning ‘heat-movement’.

  The law of conservation of energy is sometimes called ‘the first law of thermodynamics’ because it is the most basic rule governing what will happen and what won’t happen in connection with energy.

  As for the spontaneous change from an uneven distribution of energy to an even one, that is called ‘the second law of thermodynamics’.

  The second law of thermodynamics was foreshadowed as early as 1824, when the French physicist Nicolas L. S. Carnot (1796–1832) was the first to study, in careful detail, the heat-flow in steam-engines.

  It was not until 1850, however, that the German physicist Rudolf J. E. Clausius (1822–88) suggested that this evening-out process applied to all forms of energy and to all events in the universe. Clausius is therefore usually considered as the discoverer of the second law of thermodynamics.

  Clausius showed that a quantity based on the ratio of total heat to temperature in any particular body was important in connection with the evening-out process. He gave the name ‘entropy’ to this quantity. The lower the entropy, the more uneven the energy distribution. The higher the entropy, the more even the energy distribution. Since the spontaneous tendency seems to be invariably for change from an uneven distribution of energy towards an even one, we can say that the spontaneous tendency seems to be for everything to move from a low entropy to a high entropy.

  We can put it this way:

  The first law of thermodynamics states: the energy content of the universe is constant.

  The second law of thermodynamics states: the entropy content of the universe is steadily increasing.

  If the first law of thermodynamics seems to imply that the universe is immortal, the second law shows that that immortality is, in a way, worthless. The energy will always be there, but it won’t always be able to bring about change, motion, and work.

  Some day, the entropy of the universe will reach a maximum and all the energy will be evened out. Then, although all the energy will still be there, no further change will be possible, no motion, no work, no life, no intelligence. The universe will exist but only as the frozen statue of a universe. The film will have stopped rolling and we will be looking forever at a ‘still’.

  Since heat is the least organized form of energy and that which lends itself most easily to being evenly spread out, any change from any form of nonheat energy into heat represents an increase in entropy. The spontaneous change is always from
electricity to heat, from chemical energy to heat, from radiant energy to heat, and so on.

  At maximum entropy, therefore, all forms of energy that can be converted to heat will be, and all parts of the universe will be at the same temperature. This is sometimes called the ‘heat-death of the universe’ and from what I have said so far, it would seem to represent an inevitable and inexorable end.

  The ends of the mythic and the scientific universes are thus far different. The mythic universe ends in a vast conflagration and falling apart; it ends in a bang. The scientific universe, if subjected to the heat-death, ends in a long-drawn-out whimper.

  The end of the mythic universe always seems to be expected in the near future. The end of the scientific universe by the heat-death route is far off indeed. It is at least a thousand billion years off, perhaps many thousand billions of year off. Considering that the universe is at present only fifteen billion years old according to current estimates, we are clearly only in the infancy of its life.

  Yet, although the end of the mythic universe is usually described us violent and near, it is accepted because it brings the promise of regeneration. The end of the scientific universe by heat-death, though it be peaceful and exceedingly far off, seems to include no promise of regeneration but to be final; and apparently that is a hard thing to accept. People search for ways out.

  After all, processes that are spontaneous can, nevertheless, be reversed. Water can be pumped upward against its tendency to seek Its level. Objects can be cooled below room temperature and kept there in-a refrigerator; or heated above room temperature and kept there in an oven. Looked at in that way, it would seem as though the Inexorable entropy-increase could be defeated.

  Sometimes the process of entropy-increase is described by imagining the universe to be a huge and indescribably intricate clock which is slowly running down. Well, human beings own clocks that can and do run down, but we can always wind them up again. Might there not be some analogous process for the universe?

  Indeed, we don’t have to imagine entropy-decrease coming about only through the deliberate actions of human beings. Life itself, quite apart from human intelligence, seems to defy the second law of thermodynamics. Individuals die, but new individuals are born and youth is as prevalent now as it always was. Vegetation dies in the winter, but it grows again in the spring. Life has continued on I birth for over three billion years and more and shows no sign of running down. In fact, it shows every sign of winding up, for in all the history of life on Earth, life has been growing more complex both in the case of individual organisms and in the ecological web that binds them all together. The history of biological evolution represents a vast decrease in entropy.

  Because of this, some people have actually tried to define life as an entropy-decreasing device. If this were true then the universe would never experience a heat-death since wherever life exerts an influence it will automatically act to decrease entropy. As it happens, though, this is all wrong. Life is not an entropy-decreasing device and it cannot by itself avert the heat-death. The thought that it is, and that it can, arises out of wishful thinking and imperfect understanding.

  The laws of thermodynamics apply to closed systems. If a pump is used to decrease entropy by moving water uphill, the pump has to be counted in as part of the system. If a refrigerator is used to decrease entropy by cooling objects below room temperature, the refrigerator has to be counted in as part of the system. Nor can the pump or refrigerator be counted in merely as themselves. Whatever they are connected to, whatever their source of power, that, too, must be counted in as part of the system.

  Any time human beings and human tools are used to decrease entropy and reverse a spontaneous reaction, it turns out that the human beings and the human tools engaged in the process are suffering an increase in entropy. Furthermore, the entropy-increase of the human beings and their tools is greater, invariably, than the entropy-decrease of that part of the system in which a spontaneous reaction is being reversed. The entropy of the entire system, therefore, increases; always increases.

  To be sure, a given human being can reverse many, many spontaneous reactions in his life, and many human beings working together have built the enormous technological network that covers the Earth from the pyramids of Egypt and the Great Wall of China right down to the latest skyscraper and dam. Can human beings experience so enormous a rise in entropy and keep right on going?

  Again, one can’t consider human beings by themselves. They do not form closed systems. A human being eats, drinks, breathes, eliminates wastes, and these are all connections with the outside universe, conduits whereby energy enters or leaves. If you want to consider a human being as a closed system, you have to consider, what he eats, drinks, breathes, and eliminates as well.

  The entropy of a human being is raised as he reverses spontaneous actions and continually winds up that portion of the unwinding universe he can reach, and, as I said, his entropy-increase more than makes up for the entropy-decrease he brings about. However, a human being continually lowers his entropy again by eating, drinking, breathing, and eliminations. (The lowering is not perfect, of course; eventually each human being dies, no matter how successfully he avoids accident and disease, because of slow entropy rises here and there that cannot be restored.)

  However, the increase in entropy in the food, water, air, and elimination portions of the system is, once more, well above the entropy-decrease in the human being himself. For the entire system, there is an entropy increase.

  In fact, not only the human being, but all animal life flourishes and maintains its entropy at a low level at the expense of a vast increase in the entropy of its food which, in the last analysis, consists of the vegetation of the Earth. How, then, does the plant world continue to exist? After all, it can’t exist for long if its entropy rises continually.

  The plant world produces the food and oxygen (the key component of air) that the animal world lives on by a process known as ‘photosynthesis’. It has been doing this for billions of years; but then plant and animal life taken as a whole are not a closed system either. The plants derive the energy that drives their production of food and oxygen from sunlight.

  It is therefore sunlight that makes life possible and the sun itself must be included as part of the life-system before the laws of thermodynamics can be applied to life. As it happens, the sun’s entropy rises steadily by an amount that far outstrips any entropy-decrease that can be brought about by life. The net change in entropy of the system that includes life and the sun is therefore a pronounced and continuing rise. The vast entropy-decrease represented by biological evolution, then, is only a ripple on the tidal wave of entropy-increase represented by the sun, and to concentrate on the ripple to the exclusion of the tidal wave is to completely misinterpret the facts of thermodynamics.

  Human beings make use of sources of energy other than the food and oxygen they eat and breathe. They make use of the energy of wind and running water, but both are products of the sun since winds are the product of the uneven heating of the Earth by the sun and running water begins with the sun’s evaporation of the ocean.

  Human beings make use of burning fuel for energy. But here the fuel may be wood or other plant products, which are based on light from the sun. It may be fat or other animal products, and animals feed on plants. It may be coal, which is the product of past ages of plant growth. It may be petroleum, which is the product of past ages of microscopic animal growth. All these fuels trace back to the sun.

  There is energy on Earth that doesn’t come from the sun. There is energy in Earth’s internal heat and that produces hot springs, geysers, earthquakes, volcanoes, and the shifting of Earth’s crust. There is energy in Earth’s rotation, which is evidenced in the tides. There is energy in inorganic chemical reactions and in radioactivity.

  All these sources of energy produce changes, but in every case the entropy is rising. Radioactive materials are slowly decaying away and once their heat is no longer added to Earth’s internal supply, the Earth will cool off. Tidal friction is gradually slowing the Earth’s rotation, and so on. Even the sun will eventually run out of its supply of work-producing energy as its entropy rises. And the biological evolution of the last three billion years and more, which seems so remarkable an entropy-decreasing process, has done it on the basis of the rising entropy of all these energy sources and, it would seem, can do nothing to stanch that rise.