Chapter One: Energy Itself
I taught the science of body energy, or bioenergetics, at Cambridge University for many years before I realized that I did not understand what energy was. Tutorials (or supervisions, as they are called in Cambridge) are meant to be cozy but fiercely intellectual chats between a teacher and one or two students over tea and scones. However, teachers (called fellows in Cambridge) often rattle on without knowing what the hell they are talking about. And one fine day I discovered that was true of me and energy. Part of the problem with energy is that it is rather an abstract idea, so one answer to the question, "What is energy?" is, "A concept in the scientist's head." A more subtle problem is how the concept of energy has evolved historically, so that many layers of meaning, which are not always consistent, have been superimposed on the words and symbols. So take heart; if you do not at first understand the meaning of energy, it will not necessarily disqualify you from doing scientific research or teaching bioenergetics at Cambridge. In science as in life, you do not necessarily have to understand a concept in order to be able to use it. According to current scientific ideas, energy is not an invisible force field coursing through the body, moving arms and legs here and cooking up great thoughts in the brain, like some benign ghost dashing around pulling the levers of the body and mind. The modern idea of energy is rather like that of money. Money is a capacity to buy things. It comes in many forms -- coins, notes, checks, bank accounts, bonds, gold -- and it can be used to buy many sorts of things, such as hats, houses, and haircuts. Money allows the exchange of these things at a fixed rate; for example, I can exchange a fixed quantity of coins for one haircut. Now "energy" is a capacity for movement or change in a physical or biological system. It comes in many forms, such as chemical energy, electrical energy, or mechanical energy, and it can be used to "purchase" many forms of change, such as movement, chemical change, or heating. Energy quantifies the exchange between these things at a fixed rate; for example, a certain amount of heating requires the expenditure of a certain amount of chemical energy.
There is, however, one important difference between money and energy: money and monetary value are not exactly conserved. You may pay $200,000 for a house one year and sell it for $210,000 or $190,000 the next year without having done anything to the house, and the missing $10,000 does not suddenly appear or disappear from somewhere else in the economy. And you can burn a $10 bill, and the money simply disappears in smoke. Neither money nor monetary value is absolutely conserved; there is no equivalent in economics to the first law in thermodynamics. If there were, economics would be a lot easier, but we might also be a lot poorer. On the other hand, energy is strictly conserved; the first law of thermodynamics states that during any change of any sort, the total amount of energy in the universe stays the same. If you use 100 units of energy to raise a rock 100 feet in the air, when you come back a year later and lower the rock to the ground, 100 units of energy will be released. It may not be released in ways that you would want -- the energy may be released as heat, sound, or work, depending on how the rock is lowered -- but when you add up the energy released, the total will still be 100 units.
Money or monetary value is rather abstract since it can reside in very different things, such as coins or a bank account. Similarly, energy is rather abstract since it can reside in many different types of things, but is not those things; rather, energy is their capacity to produce movement or change. The energy is not something in addition to the things themselves; it is as if an accountant were looking at the situation and assessing the capacity for movement or change. If a rock is balanced at the edge of a chasm, someone might come along and work out that if the rock were to be tipped into the chasm, so much energy would be released as movement, noise, heat, on something else. Before the rock is moved, the energy does not reside in the rock or the chasm, any more than monetary value resides in coins or haircuts, because energy or monetary value is not a tenuous form of matter, but rather a way of quantifying the potential for change. Energy quantifies the capacity for movement or physical change in a situation.
Energy is like money in another way. Money does not determine how or when the money is to be spent; that is determined by the people spending it. Similarly, a rock balanced over a chasm may have a lot of energy, but this does not determine if or when the rock may fall. Rather, it determines whether the rock can fall. The presence of a million dollars does not determine how or when it will be spent, but it does mean that x number of houses, or y amount of strawberries, or z number of haircuts could be bought. Similarly, the presence of 1 million units of energy does not determine how or when the energy will be used, but it does mean that x amount of heat, or y amount of movement, or z amount of electricity could be produced.
The American physicist Richard Feynman warns us of the abstract nature of energy in his famous 1960s Lectures on Physics:
It is important to realize that in physics today, we have no knowledge of what energy is. We do not have a picture that energy comes in little blobs of a definite amount. It is not that way. However, there are formulas for calculating some numerical quantity....It is an abstract thing in that it does not tell us mechanisms or reasons for the various formulas.
So energy is not a thing or a substance. We can calculate it, and use the numbers to predict things, but we have no idea what it is in itself. It seems to be just an abstract accounting concept like money, which quantifies the amount of movement that could be produced by a particular system. How boring! On the other hand, according to the rather abstract standards of physics, energy is perhaps the most fundamental property of the world. Energy is the one thing that remains constant (is conserved) through all change. Everything can be created from or dissolved into energy, including matter itself, as demonstrated by the explosion of an atom bomb and Albert Einstein's famous equation, E = mc2. According to this rather abstract scheme of things, then, energy is the ultimate substance and fabric of the world, from which all else evolves and into which all else ultimately dissolves.
But energy itself does not produce movement or change. So what does? According to Sir Isaac Newton (16421727), all movement or change is brought about by a force. In our everyday lives, we experience only two types of force: gravitational force and contact forces. The gravitational force pulls things toward the center of the earth and causes all heavenly (and not so heavenly) bodies to attract each other. Contact forces occur when we push or pull something -- when I lift a chair, when a car hits a lamppost, or when a volcano explodes. The gravitational force occurs because every bit of matter is attracted to every other bit, causing them to accelerate toward each other. All the contact forces are actually different manifestations of one immensely powerful force: the electric force. The electric force is the force of attraction or repulsion between all charged bits of matter. The gravitational force and the electric force account for virtually all movement and change in our universe. There are two other forces known: the strong nuclear force and the weak nuclear force, but their range of action is so small that they can be observed only by breaking open the nucleus inside an atom. Thus, these nuclear forces have no apparent effect on biology or our everyday lives.
Although the gravitational force is important for large objects like us, it is not significant for small objects like a cell. The electric force is roughly one thousand million million million million million million times stronger than the gravitational force, and at the level of molecules and cells, it is the only force that matters. The gravitational force causes attraction -- that is, two bits of matter will accelerate toward each other. But the electric force causes either repulsion or attraction depending on whether the bits of matter carry the same or different charges: opposites attract; likes repel. The electron carries a negative charge; the proton carries a positive charge. All things, including our bodies, can be considered to be made up of different arrangements of protons and electrons. There are also neutrons, but they have no charge and behave a bit like an electron and a proton stuck tightly together. All bits of matter are made up of roughly equal numbers of electrons and protons. If this were not so, there would be an excess of positive or negative charge, and this would create a huge force pushing the excess charge out, leaving a roughly neutral group of electrons and protons. The power of the electric force is truly immense. If two people, standing an arm's length apart, were each to have 1 percent more electrons than protons in their bodies, they would be blown apart by an electric force sufficient to move the weight of the entire earth.
The power of the electric force is not always evident at the everyday level because most things contain almost exactly the same number of protons and electrons, so there is no net force between objects. Still, we notice this force when things get up close, so that the electrons actually get to feel each other. When we push a cup with our finger, this is the electrons on the surface of our finger repelling the electrons in the cup. Similarly, all contact forces (that is, whenever something touches, pushes, or crushes something else) are due to electron repulsion. If you want to experience directly what electrons feel like, just touch somebody's body with your hands, all that you can feel is electrons.
Essentially everything that happens in the body is due to these electrons' and protons' bumping into each other and rearranging themselves. Some arrangements of protons and electrons are more stable than others; they last longer. We call these stable arrangements molecules. As molecules collide, they may break up and rearrange, forming new molecules. Different molecular arrangements have different energies associated with them. This is due to the different arrangement of protons and electrons within them. For example, a molecule might contain a number of electrons packed close together, and producing such an arrangement would require lots of energy, because the electrons would have to be pushed together against the strong repulsion of their negative charges. But if that part of the molecule is broken apart and rearranged, then a lot of this energy will be released as the different electrons and associated molecules fly apart. Turning one arrangement or molecule into another either requires energy or releases energy, depending on whether the new arrangement has more or less energy than the old.
The essential task of animal life is to take molecules (food and oxygen) from the environment and rearrange the protons and electrons so that there is less repulsion between the electrons in the molecules produced (that is, carbon dioxide and water). This process releases energy, just as burning the food would do. However, the body cannot afford to release the energy as heat, because living organisms cannot use heat as a source of energy. Energy on its own is not enough to power life. There is something even more fundamental that drives all living processes. Erwin Schrödinger, the great Austrian physicist and creator of quantum mechanics, called it negative entropy (or negentropy). In order to understand it, we need to traverse the infamous second law of thermodynamics.
The Second Law and the Secret of Life
It is tempting to pass discreetly over the second law, to ignore it and hope nobody notices, because it is a notoriously slippery idea. However, up close, it can be awe inspiring and beautiful. Some of the most creative scientific minds have described it as one of the greatest creations of human culture. C. P. Snow in his lecture and book The Two Cultures compared the cultural value of the second law to Shakespeare's plays and suggested that for those who aspired to be called "cultured," an ignorance of the second law was on a par with an ignorance of Shakespeare's plays. The target of Snow's comments was intellectuals, and particularly Oxbridge ones, who decried the apparent ignorance of scientists in classical cultural matters and did not realize there was an alternative culture at least as deep as theirs. Whether we aspire to be "cultured" in this sense, it remains true that the second law is central to a real understanding of change, just as Darwin's theory of natural selection is central to an understanding of evolution. But the second law is slippery; there are almost as many interpretations of it as there are people interpreting.
The second law arises from the general principle that if something is randomly perturbed (jiggled around), the components of that something will become more randomly distributed. If we put some children's plastic bricks in a tin box and shake the box, the bricks will become more randomly distributed. If the bricks were initially stacked on top of each other, or in one corner of the box, or separated into their different colors, then after the shaking, they will be more randomly distributed. The bricks will become unstacked, they will spread around the box, and the colors will be mixed up. Notice that the opposite does not happen. If the bricks are initially randomly distributed in the box and we shake it up, they will not arrange themselves into a more ordered pattern. This follows a general principle that a system undergoing random perturbations will become more randomly distributed with time, not more ordered. Why? Because a random distribution is much simpler to obtain than an ordered distribution. A random distribution isn't a particular distribution; it is lots and lots of different distributions that have in common only the fact that they are not ordered, whereas an ordered distribution, such as the different colored bricks separated into piles, is a very particular distribution that can be brought about only in a small number of ways. Thus, if components like bricks are subjected to a random perturbation -- say, the bricks are randomly jumping between piles -- then it is much more likely that each perturbation will result in a more random distribution. One of the many blue bricks in the blue pile will more probably jump into the red pile than the only red brick in the blue pile jump into the red pile. Ordered distributions are less probable than random distributions. That is the essence of the second law.
The same principle may be illustrated with a pack of cards. If we start with the cards in order, arranged in suits from ace to deuce, and we then shuffle them extensively (random jiggling), we end up with a disordered arrangement of cards. But the opposite does not usually happen unless you are a card shark. There are only a few different arrangements that are considered ordered, whereas there are millions of different arrangements that are thought of as disordered. When we shuffle, the pack jumps from one arrangement to another randomly selected arrangement. If there are one ordered arrangement and a million disordered arrangements, then a randomly selected arrangement produced by shuffling has a one in a million chance of turning up the ordered selection, and a near certainty of producing another disordered arrangement.
The kind of system the Second Law deals with is usually a whole bunch of molecules bumping into each other, such as a lump of wood, or an animal, or the sun, or a cell, or the universe. The random perturbation is provided by the heat in the system -- that is, anything that is hotter than absolute zero consists of molecules jiggling around in a random fashion. The heat simply is the jiggling of the molecules, and jiggling is random in the sense that the different molecules are banging into each other in random directions at a range of different speeds and at different times. This jiggling causes the matter and energy of the system to redistribute, and because the jiggling is random, the new distribution of matter and energy will be more random than before. For example, if a bunch of molecules are initially in one corner of a box, the thermal jiggling will eventually redistribute them all over the box. If some of the molecules in the box are initially moving much faster than the others, then the random collisions will redistribute the energy more evenly. If there are initially different types of molecules in different parts of the box, then the random jiggling will mix them all together. If two liquids, say, orange juice and black currant juice, are layered on top of each other (according to the strict instructions of my four-year-old son), then they will eventually mix together, because this is a more random distribution of the molecules. If the temperature is high enough that the atoms start redistributing between molecules (that is, get torn off some and stuck onto others), then we are going to end up with a more random distribution of atoms between molecules. Thus, if two molecules can chemically react, eventually they will react.
The extent to which the matter and energy of a system are randomly distributed can be measured and is called entropy. High entropy means a random system; low entropy means an ordered system. The second law can therefore be stated in this way: During any natural change, entropy always increases. The wonderfully useful concept of entropy was invented by the German physicist Rudolf Clausius in 1850, but its real meaning in terms of atoms and molecules was discovered by the Austrian physicist Ludwig Boltzmann at the end of the nineteenth century. Unfortunately for Boltzmann, atoms were not then yet in vogue, and his explanation of change in terms of the purposeless movement of atoms was thought to undermine purpose in the universe, in a similar way to Darwin's recent undermining of purpose in biology. Boltzmann, although recognized as one of the greatest physicists of his day, suffered the scorn of his contemporaries and killed himself in a fit of depression. His gravestone in Vienna still bears his great legacy: the simple equation relating disorder to entropy: S = k.logW, where S is the amount of entropy, k is a constant number now known as Boltzmann's constant, W is the number of possible ways of arranging the component matter and energy of a system to give the same state, and the "log" in front of W effectively means that a many-fold increase in W increases S by only a relatively small number.
Motion of an object, such as a bullet, involves all the atoms moving in the same direction, at the same speed, at the same time, whereas the heat of an object involves all the molecules moving in different directions, at different speeds, at different times. When a bullet hits a wall, energy is transferred from the motion of the object to heat. The energy of the system becomes much more randomly distributed. So according to the second law, motion energy can be converted into heat energy because the matter and energy become more randomly distributed, and that is a natural and irreversible process. Heat cannot be (fully) converted to motion, because this would require the system to become more ordered. All the atoms moving in different directions at different times would somehow have to arrange for themselves to move in the same direction at the same time. That is impossible according to the second law.
Use of the word natural here is important. We could interfere with the system to make it less random and more orderly. We could arrange for the motions of the individual atoms to coordinate so that they produced an orderly motion. We could supply some fuel or motor to maintain or increase the order of the system. But any of these interventions would require continuously importing order into the system or exporting disorder out of the system. If we take into account the changes outside the system and inside the system, then the second law still holds: the total change in entropy arising from any change must always increase.
Heat is the most disorganized form of energy; therefore in any natural process, the conversion of stored or motion energy into heat will greatly increase the entropy (the energy will be more randomly distributed). That is why in virtually every process you see around you, heat is being released from some stored form of energy. Remember that doing anything generates lost heat, and we cannot reconvert that lost heat back into stored energy. In a sense, it is the conversion of other forms of energy into heat that drives all processes in the universe. If we are to continue to do things, we need to renew our stored energy continuously from somewhere else. And although we are surrounded by a vast ocean of heat energy, we cannot convert it into other forms because of the second law. Heat energy is useful only if it is supplied at a high temperature and can be disposed of at a low temperature, because the diffusion of heat from the high to low temperature is a spontaneous process, which increases entropy and therefore can be used to do some work.
But if everything in the universe tends toward disorder, randomness, and chaos, how can we explain the existence of living organisms, which are stupendously nonrandom structures? How can we explain the growth of a simple seed into a complex tree? How can we explain the creation of a bird's wing, an octopus's eye, or a spider's web? Surely, nature produces more complex, ordered, and nonrandom forms than what it started with. Has entropy decreased? Does life violate the second law? Well, we might say that life violates the spirit of the second law but not the letter of the law. We need to look at all of the starting materials and end products. When the bird's wing, octopus's eye, and spider's web were created, these were not the only changes; a lot of food was burned and heat was released. The release of this heat to the surroundings caused an increase in the entropy or disorder of these surroundings. And if we add up the increase in entropy of the surroundings and the decrease in entropy of the animal, there is a net increase in entropy. This trick gets organisms around the second law; they decrease their own entropy by importing stored energy and exporting heat energy. Thus life exports disorder in order to increase its own order. That's why Schrödinger said that life feeds on negentropy, or negative entropy.
Life is confronted with the problem that most of the processes essential to it are not spontaneous or not natural, because each process results in a more ordered state of matter or energy. For example, a cell needs to collect randomly distributed molecules and put together complex cellular structures and ordered molecules such as DNA. How is life to construct this order without violating the second law? The solution is coupling. Life couples the forbidden process that decreases entropy to another spontaneous process that increases entropy, so that there is a net increase in entropy. For example, the cell manages to concentrate inside itself molecules that are rare outside, thus decreasing entropy, by coupling this concentrating process with the transport of sodium inside, which increases entropy because there is much more sodium outside the cell than inside it. The coupling is simply done by a molecular machine, located in the cell membrane (the thin wall that surrounds the cell), which allows sodium into the cell only when it is accompanied by another molecule that the cell wants to accumulate. The molecular machine acts as a gatekeeper that couples the transport of sodium to the transport of other wanted molecules, so that the entry (or exit) of one cannot occur without the entry (or exit) of the other.
Similarly, the cell manages to make DNA by coupling this ordering-inducing process to a disordering process, the splitting of ATP (adenosine triphosphate). ATP is a general-purpose energy source within the cell, and its breakdown or disordering can be coupled by many different cellular machines to essential ordering processes, such as the synthesis of DNA. However, this cannot go on forever; in a few seconds, all the ATP in the cell will be broken down, and the cell will be full of sodium. The ATP must be remade and the sodium pumped out of the cell again. But these processes decrease entropy, so they have to be coupled to some other entropy-increasing processes. Thus, the cell requires a chain of coupling processes, which is eventually connected to the burning of food, continuously maintaining the import of food and oxygen from the environment and the export of carbon dioxide and heat. This is the key trick of life: the coupling of processes that you want but are impossible, to processes that are possible and can be continuously replenished.
The chain of energy that links every molecular event in our body does not end in the environment outside our body. The food and oxygen on which we feed to power our bodies must be replenished somewhere in the environment; otherwise, it would rapidly be depleted. Animals must feed on other animals or plants as a source of energy, which are thus linked in a food chain or web of energy. Ultimately, the plants of the world produce both the food energy and the oxygen that power us and the other animals of the world. Almost all energy on earth comes from the sun. Perhaps the ancients were right to think of the sun as a god, source of all things in the world. The sun is spewing out stupendous quantities of energy as light into empty space. A tiny fraction of that light is caught by the plants on earth and used to power the conversion of water and carbon dioxide into the complex molecules of the plant (which become food for animals) and into oxygen (which is released into the air). In terms of the second law, the conversion of earth and air into all the improbable forms of life is made possible by coupling it to the conversion of pure starlight into random heat energy.
Now that you know the secret of life and the second law, you are entitled to call yourself a "cultured" person according to C. P. Snow. However, before you rush off to that cocktail party, you had better brush up on Shakespeare's plays.
Copyright © 1999 by Guy Brown