The Energy of Life:

скачать книгу бесплатно


Hippocrates (c. 460–377 BC) is called the founding father of medicine, and his theories of disease, cure and physiology influenced medicine and biology up until the eighteenth century. However, his own life is so mythologized that it is impossible to distinguish the basic events of his life, or even whether he really ever existed. According to legend, Hippocrates was a physician from Cos, and he practised medicine in Thrace, Thessaly and Macedonia, before returning to Cos to found a school of medicine. This school flourished from the late fifth century to the early fourth century BC, producing a vast number of highly original medical texts. Copies of around seventy of these books survive. These were conventionally attributed to Hippocrates, although he probably wrote none of them himself. The defining characteristic of Hippocratic medicine was its rejection of religious and philosophical explanations of disease, and its search for an empirical and rational basis for treatment.

Since prehistoric times, disease had been thought caused largely by gods, evil spirits, or black magic. A cure could thus be effected by ejecting the sin, spirit, or magic from the sufferer via various processes of purification. In Greece, traditional medicine was practised by priest-physicians in temples dedicated to the god Asclepius. In these temples of health, disease was apparently diagnosed partly on the basis of dreams and divination, and partly on the symptoms. Cures were half rituals and spells, and half based on fasting, food, drugs and exercise. According to later legend, Hippocrates was descended from the god Asclepius and brought up on Cos as son of a renowned priest-physician. The relationship between secular medicine (represented by Hippocrates) and religious medicine (based on faith healing or magic) in ancient Greece is difficult to discern, although apparently not as antagonistic as today.

Hippocrates and his followers accepted the doctrine of the four elements as an explanation for the natural world, but their concern as doctors was with disease’s causes and treatment. The four elements – earth, fire, air, and water – cannot be seen in anything approaching a pure form in or on the body. Also they knew relatively little about the inside of the body, because dissection was prohibited on both religious and ethical grounds. So the Hippocratics concerned themselves with what they could see and use in the diagnosis of disease, particularly the bodily fluids: blood, saliva, phlegm, sweat, pus, vomit, sperm, faeces and urine. Gradually the doctrine evolved that there were only four basic fluids (humours): blood, phlegm, yellow bile, and black bile. Blood can appear in cuts, menstrual flow, vomit, urine or stools. Phlegm is the viscous fluid in the mouth (saliva) and respiratory passages and comes out through the mouth and nose in coughs and colds. Yellow bile is the ordinary bile secreted by the liver into the gut to aid digestion; it is a yellow-brown fluid that colours faeces. The identity of black bile is not entirely clear, perhaps originally referring to dark blood clots, resulting from internal bleeding, which may appear in vomit, urine or faeces. However, the four humours did not only refer to these particular fluids, but were thought to be the body’s basic constituents. Health was thought to be due to the balance of these humours, and ill health an imbalance of the humours. Epilepsy was, for example, thought to be caused by an excess of phlegm in the brain blocking the flow of pneuma (vital spirits) to the brain. Thus treatment sought to restore the balance between the humours by removing the humour that was present in excess, for example by bloodletting, purging, laxatives, sweating, vomiting, diet or exercise.

The four humours (blood, phlegm, yellow bile, and black bile) were associated with the four elements (air, water, fire and earth), the four primary qualities (hot, cold, dry and wet), the four winds, and the four seasons. A predominance of one humour or the other gave rise to four psychological types. Thus, the ‘sanguine’ type, resulting from a dominance of blood, was cheerful and confident. ‘Phlegmatic’ types (with too much phlegm) were calm and unemotional. ‘Choleric’ or ‘bilious’ people (with too much yellow bile) were excitable and easily angered. ‘Melancholic’ types (too much black bile) were, obviously, melancholy, that is sad or depressed, with low levels of energy. This was the earliest psychological classification of character or temperament, and was used to categorize different people right up until modern times. No obviously superior way of classifying temperament has, in fact, yet been devised. The theory of the four humours dominated medical thinking until about three hundred years ago. Many patients were still being bled even in the nineteenth century.

The Hippocratics and Greeks generally believed in positive health – health could be improved much further than the absence of illness towards well-being. Modern medicine is mainly concerned with negative health (i.e. illness), and how to restore us to health, rather than with helping us feel ‘on top of the world’. The Hippocratics were much concerned with regimen or lifestyle, both in health and disease, mainly involving the correct balance of food and exercise. The importance of exercise to both physical and mental health was recognized, and was institutionalized in gymnasia where exercise was practised on a social basis. If you had gone to Hippocrates in 400 BC (assuming you could find him) complaining of lack of energy he might have given you a detailed regimen involving an exercise programme, with a warning about too much or the wrong type of exercise; a diet, particularly including strained broths; a lot of hot and/or cold baths, and massages; some sex (if lucky); and some obscure advice about the relations between your energy and the wind direction, season of the year, etc. This would have been, in general, a reasonably effective regimen, and you would be lucky to get better advice today from your doctor.

Aristotle (384–322 BC) was a colossus of thought, straddling the end of classical Greece and Renaissance Europe. He dominated the world of the intellect, sometimes as a benign sage and other times as malevolent dictator. His thoughts were worshipped to such an extent that they circumscribed any attempts at original thought, until their eventual rejection by Renaissance Europe, when he was blamed for stifling two thousand years of thought. Much of Aristotle’s influence derives from his having been a pupil of Plato (possibly the greatest thinker ever), and then tutor to Alexander the Great (possibly the most successful conqueror of all time).

Aristotle’s views of the physiology and energies of life were derived mostly from Empedocles, Hippocrates and Plato. Nutrition, vital heat and pneuma (vital spirit) were pivotal to this view. The heart was central to the body, the origin of consciousness and the instrument of the soul, and the source of heat, pneuma, blood, and movement for the rest of the body. Pneuma was an air-like substance or spirit, containing vital heat, which was always in rapid motion, and as such was a source of both heat and motion inside the body. Pneuma was derived from air, and brought through the mouth, nose and skin to the heart, where it supplied the vital heat. A steady flow of nutrient fluid from the gut supplied the heart, and the heating of the fluid within the heart produced blood. The blood and pneuma were then distributed through vessels to the rest of the body, where the blood coagulated to form the tissues of the body under the influence of the ‘nutritive soul’. There was no circulation of blood, rather the blood was produced in the heart (and liver and spleen) and then distributed to the tissues, with no return flow. Many vessels (the arteries) were thought to be hollow (as indeed many are if the blood escapes from them after death), and were, thus, thought to carry air or pneuma through the body. The brain cooled the blood, and functioned to prevent the blood from overheating. The muscles were simply a protective layer, keeping the rest of the body warm, and had no function in movement. Nerves, as such, were unknown, as most are difficult to see; but large nerves and tendons were collectively called neura and were thought to function in movement of the limbs, by acting as cords pulling the bones. The pneuma supplied the ‘go’, energy or movement throughout the body.

Aristotle’s pneuma was also the motivating force outside the body – in the physical world. According to his mechanics, the natural state of things was rest rather than movement; so that the continuous movement of an object such as an arrow in flight required pneuma to be continuously pushing the arrow from behind. Thus we can see that pneuma was energy for Aristotle, although of course it had a rather different role in classical thinking. Aristotle was also partly responsible for the theory of the four qualities: hot, cold, wet, and dry, which were components of the four elements. Thus earth was cold and dry, water cold and wet, air hot and wet, and fire hot and dry. This became a very important doctrine in later medicine and alchemy, because it gave a key as to how to alter the ratio of the elements; thus, for example, water could be converted to air by heating, or air could be converted to fire by drying.

Aristotle was the first authority to use the term energeia, from which we derive the word ‘energy’. But he used it to mean the ‘actual’, as opposed to the ‘potential’, as he had an obscure theory that ‘change’ involved turning from a potential thing into an actual thing. So when something happens, a potential happening changes into an actual happening. Thus for Aristotle energeia was tied up with change and activity, but in what seems now a rather obscure and abstract way.

Although Aristotle’s view of physiology and energetics was most influential, it was far less original and interesting than that of Plato. Plato was not really interested in physiology, as he had his mind set on higher things, but he wanted to find a physical location for the various parts of the soul that he had identified. For, according to Plato, the body is peopled by a bickering community of souls, ruled over by a somewhat prissy head. The immortal soul is in the head, and the mortal soul located from the neck down. The courageous part of the mortal soul is found above the diaphragm, where it can both listen to reason (from the head) and subdue the lower regions. This soul’s main home is the heart; when the head thinks that the passions are out of control it informs the other organs, and the heart starts leaping with excitement and overheating. The lungs can then save the day by cooling and providing a cushion for the overtaxed heart. Below the diaphragm dwells the ‘appetitive’ soul, which while necessary for life needs to be kept chained, far from the seat of reason. This part of the soul is controlled by the liver, capable of listening to reason. The liver regulates the nether regions either by contracting to block passages causing pain and nausea, or by spreading cheerfulness and serenity to the surrounding parts of the soul. The length of the gut is intended to prevent food passing through too quickly, which would cause an insatiable appetite, and make mankind impervious to culture and philosophy. The spinal marrow is called the universal ‘seed-stuff’ (also the source of semen) fastening the soul to the body. The different kinds of soul are found in various parts of the marrow, while reason and intellect occupy the brain. This community-of-souls theory of the body shows how appealing, but empty, intentional explanations of physiology can be. In order to progress, the supernatural had to be replaced by mechanical causes and energy as the source of change.

The deaths of Aristotle and Alexander in 322 and 323 BC respectively marked the end of classical Greece. But Alexander had spread Greek culture across the known world, ushering in the age of Hellenism, which was a fusion of Greek and Persian culture. Hellenism’s most successful centre was in Alexandria, briefly flourishing under Ptolemy I. A former pupil of Aristotle, Ptolemy attracted some of the greatest Greek scientists and thinkers to Alexandria’s Museum and Library. Two brilliant physicians, Herophilus and Erasistratus, were able for the first time to practise dissection of the human body there and used this to great effect. This had been impossible previously due to the commonly held assumption that the body retained some sensitivity or residual life after death. Changing beliefs about the soul’s relation to the body enabled Herophilus and Erasistratus to dissect dead humans, and even, it has been claimed, live criminals. The result caused a revolution in anatomy: the exploration of a whole new realm below the human skin. The nerves, and their relation to the brain and muscles, were discovered. The brain was explored and the fluid-filled cavities within (ventricles) were thought to be filled with a new form of pneuma: psychical pneuma (animal spirits). This psychical or mind pneuma radiated out from the brain, through the nerves, to energize the muscles. However, Alexandrian scientific creativity gradually declined and the influence of eastern mysticism increased.

In the second and first centuries BC, Rome swept the political stage while largely adopting Greek culture and thinking. Into this new world was born Galen (AD c. 129–216), antiquity’s last great physician and biologist. An architect’s son from Pergamon, he studied philosophy then went to Alexandria to learn dissection. Returning to Pergamon, he became surgeon to a school of gladiators, where he gained invaluable experience in treating wounds. In AD 169 Galen was summoned to Rome to become personal physician to Marcus Aurelius, the Philosopher Emperor. These duties do not seem to have been too onerous as Galen continued his writing and scientific work, in the end producing over 130 books. Many are commentaries on and syntheses of previous medical knowledge, including textbooks and treatises on almost all diseases, treatments and methods of diagnosis. These books became the central texts of medicine for fifteen hundred years. Galen was seen as a kind of medical theologian, for whom anatomy was both praise and veneration of the one true God. And this, twinned with his interpretation of the body in Aristotelian terms, guaranteed the acceptance of his writings by later Christian and Islamic authorities.

Galen’s doctrine of pneuma synthesizes earlier ideas of the Hippocratics, Aristotle, the Alexandrians and Stoicism (a philosophy founded by Zeno). Pneuma can be translated as ‘airs’, and was thought to be an invisible force within the air. Pneuma was translated into Latin as spiritus, but is most naturally translated today as ‘energy’. To the Stoics, pneuma was a non-material quality or form imposed on matter. Pneuma pervaded the universe and was the vehicle of cosmic ‘sympatheia’, by which each part of the universe was sensitive to events in all others. Pneuma acted as a force field in the air, immediately propagating movement to the edge of the universe and then back again. This is reminiscent of modern concepts of sound waves or of electromagnetic waves moving through the air. Inside the body, pneuma pervaded the blood vessels and nerves and enabled the transmission of sensitivity, movement and energy.

Galen distinguished three different kinds of pneuma inside the body: natural spirit, vital spirit and animal spirit. These were produced by the three main organs and their associated faculties or souls (the idea was derived from Plato). The liver, hub of the appetitive soul and supposed source of the veins, produced natural spirits. The heart, centre of the spirited soul and source of the arteries, produced vital spirits. And the brain, home of the rational soul and source of the nerves, produced animal spirits. The liver took digested food from the stomach and guts, concocting it into dark, venous blood containing natural spirits, which when distributed to the rest of the body was assimilated forming the substance of the organs. This was the basis of the appetitive (or nutritive) faculty of the liver. Taking venous blood, the heart concocted it with pneuma, derived through the lungs from the air, producing red arterial blood, full of vital spirits. These vital spirits, distributed throughout the body by the arteries, were then responsible for all other living processes, apart from those of movement and thought. The brain transformed vital spirits into psychical spirits, which then became responsible for consciousness, and when distributed by the nerves, for muscle movement and sensation.

Pneuma is the closest we get in antiquity to the modern concept of energy. It is a non-material, potential form of motion, action and heat, and its transformations correspond to the transformations of energy. The ghost of pneuma still haunts the modern idea of energy, but has been transmuted into an altogether more pragmatic concept by today’s more materialistic scientists.

After Galen, there was little innovation in Greek and Roman science and an increasing emphasis on mysticism and theology. In the fourth century, the official religion of Rome became Christianity, at that time diametrically opposed to the scientific spirit. In the fifth century, the western half of the Empire was invaded by German tribes, ushering in the Dark Ages, which lasted almost a millennium. The eastern, Greek-speaking side of the Empire lasted much longer, gradually diminishing in power. In the seventh and eighth centuries, the Islamic Arabs conquered Syria, Egypt, North Africa and Spain, absorbing Greek knowledge. Although it was not until the eleventh century and later that Christian Europe was finally able to reabsorb Greek learning from the Arabs, and, at last, to spark the Renaissance.

Alchemy forms a bridge between the ancient Greek and Roman learning and the birth of modern science in seventeenth-century Europe. While the alchemists’ quest started two thousand years ago in Alexandria, China and India, as late as 1680 Isaac Newton still devoted most of his time to the mysterious art. Because it existed through the dark ages of knowledge and science, alchemy reflected the time’s religious, symbolic and mystical forms. But it also kept many of its practitioners in contact with classical knowledge and experimental science. The alchemists appear to modern eyes as a bunch of wacky mystics. It seems incredible that sober citizens came up with this bizarre combination of chemistry and religion. Why not engineering and sex, or poetry and gardening? However, many alchemists were intent on the very practical goals of limitless money and life everlasting. What could be more modern than that? Unfortunately for them, the theories of alchemy were completely wrong.

The importance of alchemy to our story is that it attempted at least to understand what things are made of, and much more importantly how they change. If we look at a stone or egg naïvely, it is hard to see what they consist of and where their potential for change comes from. What is it about an egg that enables it to turn into a chicken? What is it about a piece of wood allowing it to burn? What is it about a lump of gold that makes it last forever? The alchemists put all these questions into the fire. Fire was the great transformer and transmuter: separating metals, distilling essences and cooking food. In many ways the alchemist was a cook, his technology was derived from the kitchen, and he sought to transform his raw materials, through recipes, herbs, and inspiration into perfection. The alchemist also sought to isolate (by distillation and other methods) the essence or spirit of things, as a metal is isolated from ores or alcohol distilled from wines or a drug ‘purified’ from a plant. They thought adding the essence of gold (known later as the ‘philosopher’s stone’) to other metals would turn the base metals into gold. Unfortunately for the alchemists, they did not yet realize that gold was an unchangeable element, more fundamental than earth, fire, air or water and that there was no essence of gold to be given to other metals. The alchemists’ real achievement was that by their slaving over a hot stove and forging mental concepts, they slowly transformed the categories and concepts by which matter was seen, eventually enabling the evolution of chemistry and biochemistry.

What have we learnt from our journey through the scientific progress of the classical world? From Empedocles, Aristotle and the Atomists, we discovered that the world and its changes do not have to be understood in terms of the wishes and desires of gods, spirits or even matter itself. It can rather be explained in terms of the structure and interactions of a small number of basic particles or elements, each too small to see, but that when mixed together make up visible matter. The changes we see are due to forces of attraction or repulsion between these particles, leading to changes in the composition of matter. From Hippocrates and Galen, we learnt that death and disease are not due to the will of gods, devils or sorcerers, but can be explained in terms of the workings and malfunctions of the body machine. And this can be understood in terms of the body’s various solid organs with different functions, the various vital liquids that flow within and between them, and the various invisible spirits or gases that animate the body. However, this knowledge does not explain how someone moves a hand by willing it, how thought is possible, or how life differs from death. Our journey must continue into the modern world in pursuit of the energy of life.

THE ENLIGHTENMENT

Our modern world was sparked into existence by the scientists and thinkers of seventeenth and eighteenth-century Europe. Without their intervention, we could now be living very differently, perhaps in some sort of impoverished, fundamentalist state. But it required revolutions and counter-revolutions, heroes and anti-heroes, blood and tears to achieve the transformation of thought that came to be known as ‘The Enlightenment’.

It was the work of four scientists in particular that prepared the ground for this new scientific approach. Their discoveries exploded the medieval conventions of cosmology. The first scientific bombshell unleashed on an unsuspecting medieval world was the discovery that the earth was not at the centre of the Universe. Copernicus (1473– 1543) wisely did not ever openly state this while alive, but the shockwaves from his heliocentric theory rocked the medieval church nonetheless. Then, Kepler (1571–1630) showed that the planets do not move in circles, but ellipses. Furthermore, Galileo (1564–1642) used a telescope to show that all was not perfect among the ‘heavenly bodies’; the moon was pitted with craters and volcanoes, Jupiter had moons, and the blanket of the Milky Way in fact consisted of millions upon millions of stars. Isaac Newton (1642–1727) then went on to show that the planets were not a law unto themselves, but rather followed the same rules as everything on earth.

Even more fundamentally important, Kepler, Galileo, and Newton stated that everything, ranging from teapots to planets, ‘obeys’ mathematically precise, mechanical ‘laws’, conjuring up a clockwork universe, policed by cold, mechanical ‘forces’. There was no more room for spirits, gods or God. No room even for Empedocles’ forces of love and strife. Things did not move (or even stop moving) because they wanted to do so, but because they were ‘forced’. According to Newton’s (and Galileo’s) first law of motion, movement itself was no longer a sign of life or spirit. Only a change in speed or direction was an active process, and this was due to an external ‘force’. Thus, amazingly, all movement in the world, apart from that of living animals, could be explained as passive and mechanical. The non-living world suddenly became frighteningly cold, empty and dead. In place of spirits, forms and purposes, there were forces. In fact, the ‘forces’ that inhabited Newton’s universe were not so radically different from the preceding ‘spirits’. The new ‘forces’ were unexplained and inexplicable, but had an inanimate mechanical basis, as opposed to the living freedom of ‘spirits’. These forces rigorously obeyed precise, mathematical laws, whereas the spirits had followed their desires. The technological wonder of the age was the mechanical clock; this in turn became a metaphor for the Universe itself. With the invention of the clock, Time itself began to tick, and the whole Universe was forced to beat in time. But it was not only the non-living things that were forced to bow to the new mechanical spirit of the age. René Descartes (1596–1650) proposed that animals were also purely mechanical devices, automata with no feelings or consciousness. The processes of the body could be explained just using mechanical laws. Thus, for example, the nerves acted as pneumatic pipes, transmitting pressure changes of animal spirits (psychical pneuma) at the nerve endings to the brain, and from there through other nerves to the muscles, where the pressure inflated the muscles.

‘Now according as these spirits enter thus into the concavities of the brain, they pass thence into the pores of the substance, and from these pores into the nerves; where according as they enter or even as they tend to enter more or less into the one or the others, they have the power to change the shape of the muscles in which these nerves are inserted, and by this means to make all the limbs move.’

He went on to compare the nervous functions of the body and mind to the automatic puppets, then fashionable, which, driven by hydraulic pipes, could move and even seemingly speak.

Descartes did leave a small bolthole for the soul in the pineal gland, a small almond-shaped organ at the centre of the brain. He suggested the soul was radically different to matter and not subject to the laws of physics, but interacted with the body, through the animal spirits inside the pineal gland. The soul consisted of an unextended, indivisible, thinking substance, constituting the mind, all thoughts, volitions and desires. But all else on earth, including the human body and brain, was a vast clockwork mechanism.

Descartes has been much demonized as the inventor of ‘Dualism’, which purported that the world consists of two radically different substances: mind and matter. Dualism is, however, an ancient concept present in all early cultures; in Classical Greece, it is Plato’s concept of two separate worlds of appearances and perfect ideas, and in Aristotle’s substance and form; it is consistently found throughout Hindu, Jewish, Christian and Islamic thought as the separation of body and soul. Descartes did not invent Dualism. He was, on the contrary, a radical materialist, considering almost everything to consist solely of one substance, matter, but perhaps his nerve failed when it came to a denial of the soul. It is conceivable Descartes might have done this were it not for the Inquisition, which had, in 1616 and 1633, condemned Galileo for his heretical scientific beliefs.

Whether Descartes intended it or not, his and other mechanical philosophies separated body and mind even further, so that they were commonly regarded as radically different. The body and brain was seen as a cold machine and analysed in relation to the latest technical toy, which ranged across clocks, levers, hydraulic puppets, steam engines, electric robots and electronic computers. Whereas the mind became some wishy-washy, non-material thing, too slippery to analyse, and best left to theologians and philosophers to chew over. Consequently the trail to body energy and mind energy splits in two here, only rejoining relatively recently.

One of the world’s greatest philosophers, mathematicians and scientists, Descartes appears to have been intrinsically lazy. Rarely getting up before midday, he worked short hours, and read little. Where did he find the energy for his great works? One answer may lie in his lack of routine. He had no need of a job, as after selling his father’s estates he lived off his investments. So he immersed himself in his studies and whenever boredom threatened he joined an army – trying out those of France, Holland and Bavaria. He was sociable, but when friends distracted him from his conceptual tasks, he moved away. Descartes never married, and his only natural child died at five, so there was never any need to adapt to a domestic routine. He was capable of short bursts of extreme concentration. On a cold morning of the winter of 1619–20 when he was with the Bavarian army, Descartes climbed into a large oven to keep warm. He stayed in there all day thinking, and when he eventually emerged had half completed his critical philosophy, which then became the foundation of modern philosophy. This anecdote stresses the importance of removing all external distractions to intense thought. But Descartes would never have managed this feat without also removing the further internal distractions of routine thoughts, feelings and desires. And, most importantly, he would never have got anywhere without supreme self-confidence. Only powered by optimistic egotism could he reject all previous thinking, rebuilding the conceptual map of the world. Confidence is the sine qua non of creativity. Descartes’ power finally gave out when lured to Sweden by Queen Christina, he was impelled to give her daily lessons at five in the morning. This proved too much for his weak constitution and he was dead within six months.

Although Descartes tried, he didn’t succeed in his application of the new mechanical approach to biology. But, in the hands and mind of William Harvey (1578–1657), this approach yielded a remarkable success with his discovery of the circulation of the blood. Blood had been thought made in the liver and heart, passing directly from the left to right sides of the heart, and then out to the rest of the body, never returning to the heart; although it might ebb and flow in the same vessels. The heart’s beat was thought due partly to breathing and partly to the formation of heat and spirits inside the heart. Thus the heart was not thought to pump the blood. Harvey showed by experiment and quantitative argument that it received as much blood as it pumped out. It was not making blood but circulating it. The heart was not an alchemist, but a mechanical pump. Furthermore, Harvey proved it was a double pump: veins brought blood from the rest of the body to the right side of the heart, which pumped the blood to the lungs; it returned from there to the left side of the heart, then was pumped to the rest of the body, through the arteries. It is telling that the function of the heart and vessels was elucidated by the use of a mechanical analogy, inspired by a pump and pipes for circulating water.

There was one glaring hole in Harvey’s scheme. He could not see how the blood got from the arteries, through the organs and back to the veins. This was because the vessels involved, the capillaries, were too small for Harvey to see. So it was left to Marcello Malpighi (1628–94) to complete our image of the circulation by finding the capillaries using the newly discovered microscope. The microscope opened up a new miniature world to discovery, just as the telescope had laid bare the heavens, and the dissecting knife had opened the body beneath the skin. The first users of the microscope must have experienced the thrill of entering unknown territory. Malpighi described for the first time the structure of the lungs, spleen, kidneys, liver and skin. Many features of the human body still bear his name (such as the Malpighian tubes of the kidney), just as the explorers of sea and land left their names on the Americas. Antoni van Leeuwenhoek (1632–1723), a Dutch draper and pioneer microscopist, discovered striped muscle, sperm, and bacteria. And then it was the English scientist Robert Hooke (1635–1703) who first saw and named ‘cells’, but failed to recognize their significance.

Comprehension of the microscopic structure of living things is essential to any understanding of how they work. In this respect they differ from mechanical machines, which are constructed on a macroscopic level from components that at a microscopic level are both homogenous and uninteresting. By contrast, living things appearing to the naked eye as fairly simple, reveal mindboggling complexity at a microscopic scale. This vertiginous intricacy continues down to the atomic scale. Both the mechanical biologists, and all previous generations of biologists were, of course, completely unaware of this vital piece of knowledge. Some biological functions (such as how the blood circulates) are understandable at the macroscopic level but the most important secrets (such as why the blood circulates) are located on a molecular scale, beyond the reach of even the microscopists. So, mechanical biologists made relatively little progress, despite their occasional breakthroughs with the circulation of the blood and the optics of the eye.

In reaction to the mechanical (and chemical) explanations of life proposed in the seventeenth century, many scientists and thinkers defended life as radically different from the non-living, due to the possession of a ‘vital force’. One such vitalist was Georg Ernst Stahl (1660–1734), who explained life and disease as the actions of a sensitive soul or ‘anima’, inhabiting every part of the organism preventing its decay. This ‘animism’ was an example of ‘vitalism’, the belief that life was not explicable in purely mechanical and chemical terms, harking back to Aristotle and earlier. Stahl was also a chemist, and proposed the infamous phlogiston theory. This theory interpreted combustion, i.e. burning with its accompanying flame and heat, as due to the release of a special substance called phlogiston, a stored heat energy. Stahl believed that plants took phlogiston from the air, and incorporated it into their matter, so if the plant was then burnt (as wood or straw) the phlogiston could escape into the atmosphere again. Or if, alternatively, the plants were eaten by animals, phlogiston could be released by the animal’s respiration, a kind of combustion inside the body. The phantom of phlogiston beguiled chemists for about 100 years until finally extinguished by Lavoisier, who also disproved Stahl’s vitalism. However, Stahl had already died in a state of severe depression long before the demise of his theories.

This historical journey has led us to a cold and abstract world of science, stripped bare of gods and spirits, ruled instead by laws and forces. We have ventured below the skin of appearances, and must travel inwards to ever smaller scales if we are to penetrate the meaning of life. The human body has become a machine, to be taken apart piece by piece. But the next veil of mystery which hides the secret of life is not a physical or mechanical one. The old dream of the alchemists is suddenly to bear fruit in the form of the chemistry of life.

THE REVOLUTION

Human attempts to find the secret to the energy of life had stalled for a thousand years but now were finally beginning to make some progress. This was due to the startling achievements of one man: Antoine Laurent Lavoisier (1743–1794), creator of the Chemical Revolution and victim of the French Revolution. Aristotle, Galen, Paracelsus, Stahl and others had all recognized that there was some relation between breathing, heat and life but the nature of this relation was no longer clear. Harvey had shown that blood circulated from the lungs to the rest of the body and back again, via the heart, but why did it circulate in this way? Was it bringing something to or removing from the tissues? The analogy between life and combustion had been noted, but combustion was seen as a kind of decomposition, so its relevance to life was still unclear.

Several British scientists had shed light on these mysteries. Robert Boyle (1627–1691) discovered an animal could not survive long in a jar after the air was removed by a vacuum pump, suggesting animal life is dependent on air or on some component of air. Boyle’s assistant, Robert Hooke (1635–1703) showed that the mechanical movement of the chest in breathing was inessential to life, since he was able to stop the chest moving in animals while maintaining life by blowing air in and out with bellows. Richard Lower (1631–1691), a pioneer of blood transfusions, showed that the colour change in blood from blue-black in the veins to red in the arteries occurred as it passed through the lungs.

Incredibly, some seventeenth-century scientists believed that life was powered by something akin to gunpowder. The invention of gunpowder in the late middle ages had led to the belief that its components (sulphur and nitre) were also responsible for thunderstorms, volcanoes and earthquakes. This supposition was apparently confirmed by the sulphurous smell of volcanoes and thunderstorms. Lightning was thought to result from a nitre-like component of air, the nitrous spirit. It was proposed that this nitrous spirit was extracted from the air by the breathing body, then combining with sulphurous compounds already contained in the body to produce a combustion – the explosion of life. The gunpowder theory of life is another fascinating example of how technological change provided new analogies and innovative ways of thinking about biology.

Between 1750 and 1775, the main gases were discovered by British chemists: carbon dioxide by Joseph Black in 1757; hydrogen by Henry Cavendish in 1766; nitrogen by Daniel Rutherford in 1772; and oxygen independently by Joseph Priestley in 1774 and the Swedish chemist Karl Scheele in 1772. However, these gases were not considered distinct chemical substances, but rather, types of air, as Empedocles’ four elements theory still held sway – 2,200 years after his death. So, for example, carbon dioxide was known as fixed air, and oxygen as dephlogistonated or fire air. But the scientific stage was set for a revolution: the overthrow of the four elements, the extinction of phlogiston, the rejection of vitalism, and for the creation of chemistry and physiological chemistry.

Lavoisier was an unlikely revolutionary: his father was a lawyer and his family was part of the prosperous French bourgeoisie. He received the best possible education and studied law, gaining an interest in chemistry from a family friend. The French Academy of Sciences had been in existence since 1666, and at only 21, Lavoisier decided he wanted to be a member. He successfully investigated various methods of public street lighting, and was awarded a gold medal by the king and at just 25 was elected to the Academy. He then embarked on the series of chemical experiments that was to reshape the world of science. But, like most other contemporary scientists, he had to finance his own experiments, so he used his maternal inheritance to purchase membership of a tax-collecting firm. While this provided him with financial security, it was to eventually prove fatal, as tax collectors were not popular at all after the French Revolution. His career did, however, also provide him with an introduction to his thirteen-year-old future wife, Marie, the daughter of another tax collector. This turned out to be a wise move, as Marie rapidly became a proficient scientist herself, serving as an able assistant to all Lavoisier’s works.

In 1775 Lavoisier was appointed scientific director of the Royal Gunpowder Administration, and started working on methods of improving the production of gunpowder and on the general nature of combustion, oxygen and respiration. When he finally disproved the phlogiston theory, the Lavoisiers staged a celebration in which Marie dressed as a priestess, burning the writings of Stahl on an altar. But 1789, the year of publication of Lavoisier’s great work Traité élémentaire de chimie, also marked the start of the French Revolution. Although he served in the revolutionary administration, his bourgeois and tax-collecting credentials finally told against him, and he was imprisoned during the Reign of Terror. Marie was given the chance to plead for his life, but chose to energetically denounce the regime instead. Lavoisier was tried and guillotined in 1794.

Lavoisier’s first target was the theory of the four elements. Alchemists had found that boiling water for a long time resulted in the disappearance of water and appearance of a solid residue. They thought this resulted from the transmutation of one element – water – into another – earth – by the action of heat or drying. We now know the solid residue is derived partly from salts dissolved in impure water and partly from the container in which the water is boiled. Lavoisier showed this by boiling purified water in a sealed glass container for one hundred and one days. He found that a small amount of solid matter appeared in the water but by weighing the matter, water and container demonstrated that all this matter was derived only from the container, thus proving water could not be transmuted into earth.

Lavoisier next turned his attention to the burning of metals. Heating metals results in a rusting of the surface, which had been compared to combustion. But according to phlogiston theory (equating phlogiston with the element of fire) combustion results from the release of phlogiston from the material into the air, and should thus result in a decrease in weight of the remaining material. Lavoisier tested this by measuring the weight of the metal before and after heating. He found that the metal always gained weight after heating; and furthermore, part of the air around the metal disappeared after the heating. Thus, the phlogiston theory of metal combustion could not be correct: Lavoisier interpreted his findings to mean that during the heating of the metal, some of the air combined with the metal to form rust, thus increasing the weight of the metal. But what was it in air that combined with the metal?

At this point (October 1774) Joseph Priestley visited Paris, dining with Lavoisier and other French scientists. This crucial meeting was to provide the essential key to Lavoisier’s research, but also resulted in the two scientists’ long-running, bitter dispute over scientific priority and plagiarism. Priestley (1733–1804) was a Presbyterian minister from Yorkshire who developed a surprising bent for science. While investigating the properties of carbon dioxide, derived from the brewery next door, Priestley discovered that when the gas was dissolved in water, it produced a pleasant drink (soda water, present in most soft drinks today). He received a prestigious medal from the Royal Society for this invention and was subsequently recruited by the Earl of Shelburne to be his secretary and resident intellectual. Priestley set up a laboratory at Shelburne’s country estate and proceeded to isolate a number of gases. In August 1774, Priestley first isolated oxygen by collecting the gas resulting from heating mercuric oxide. He found a candle burned more brightly and a mouse survived longer in a jar of this gas than in ordinary air. Priestley considered the new gas to be a variety of air (‘pure air’) and adhering to the phlogiston theory, later named it ‘dephlogisticated air’. At this crucial point Shelburne took Priestley to Paris and at a fateful dinner with Lavoisier, Priestley told of his recent experiments. Whether or not this meeting was the inspiration for Lavoisier’s subsequent experiments was later hotly disputed. But Lavoisier immediately repeated Priestley’s experiment of producing oxygen by heating mercuric oxide, realizing that this new gas must be the substance in air combining with the heated metal to produce rust (metal oxides). But Lavoisier interpreted the new gas as a separate substance (or element), not a variety of air, and later named it ‘Oxygen’ – which is Greek for ‘acid former’, because he believed (wrongly) that all acids contained some oxygen. In April 1775, Lavoisier presented his findings at the French Academy without reference to Priestley, claiming he had independently discovered oxygen. Priestley subsequently disputed his priority in the discovery of oxygen. There now seems little doubt that Priestley and Scheele discovered oxygen, but because they used the phlogiston theory and only had a crude conception of chemical elements, they failed to interpret their findings as a new substance.

Another bitter dispute followed over the composition of water. Water was still regarded as an element, but Priestley, Cavendish and James Watt (famous for his discovery of the steam engine) had found that if a mixture of hydrogen and oxygen (or air containing oxygen) was ignited with a spark, then water was produced. They were, however, slow to publish their findings. An assistant of Cavendish visited Paris in 1783, innocently telling Lavoisier of their findings on the production of water from hydrogen and oxygen. Lavoisier immediately returned to the laboratory repeating the experiment, and went even further by reversing it; he heated steam to produce oxygen and hydrogen. He swiftly published the result, claiming priority for the discovery. This understandably caused a furore. But the important knowledge was that water was not, as previously thought, an element, but a combination of oxygen and ‘hydrogen’ (another name coined by Lavoisier, meaning ‘generator of water’). At last the four elements theory was falling apart and something had to take its place. Lavoisier provided that new system, essentially modern chemistry, according to which there are many elements, including oxygen, hydrogen, nitrogen, carbon and phosphorus, which can combine in various ways to produce compounds, which depending on their nature and conditions may be either solids, liquids, or gases.

Lavoisier’s key contribution here was to accurately measure the change in weight and to use the principle of conservation of mass – the idea that regardless of what you do to an object it will not change in weight (as long as no mass escapes). Before Lavoisier’s breakthroughs it was not clear whether matter could appear or disappear during reaction or transformations. Lavoisier showed by weighing that the mass stayed the same during a reaction, and explicitly stated the principle of Conservation of Matter: matter could not be created or destroyed. He used this principle to track where the matter was going in a whole series of reactions. Because of Lavoisier’s principle, contemporary improvements in weighing techniques contributed to the development of chemistry, as much as the microscope contributed to biology. He also provided a nomenclature for chemicals, still in use today. All these changes amounted to a Scientific Revolution, which transformed alchemy into chemistry. The new system was rapidly adopted throughout Europe, only rejected by a few die-hard phlogiston theorists, including perhaps unsurprisingly, Priestley. There was no love lost between these two great scientists. Priestley, the experimentalist, regarded Lavoisier’s theories as flights of fancy; while Lavoisier, the theoretician, characterized Priestley’s investigations as ‘a fabric woven of experiments hardly interrupted by any reasoning’.

Priestley moved to Birmingham in 1780 and joined the Lunar Society, an influential association of inventors and scientists including James Watt, Matthew Boulton, Josiah Wedgwood (engineer and pottery manufacturer), and Erasmus Darwin (poet, naturalist and grandfather of Charles). In 1791 Priestley’s chapel and house were sacked by a mob angered at his support for the French Revolution. He fled to London, and then, in 1794 at sixty-one, emigrated to America, settling in Pennsylvania, and becoming one of the New World’s first significant scientists.

Lavoisier then teamed up with Pierre-Simon de Laplace, one of the greatest mathematicians in France. They wanted to investigate the relation between combustion and respiration. Combustion is the process of burning, usually accompanied by flame, such as the burning of a candle. Respiration had originally described breathing, but it had been discovered that this process was associated with the consumption of oxygen and production of carbon dioxide; ‘respiration’ thus came to stand for this process of gas exchange by organisms. Both combustion and respiration consumed oxygen from the air, replacing it with carbon dioxide and both produced heat. But could the conversion of oxygen to carbon dioxide by a living animal quantitatively account for all its heat production? In other words, was respiration really combustion, accounting for the heat produced by animals? They decided to compare the heat and carbon dioxide production of a respiring guinea pig and of burning charcoal (pure carbon). Lavoisier and Laplace invented a sensitive device to measure heat production, although it only worked well on days when the temperature was close to freezing. When, at last, everything was working, they found the burning of charcoal and the guinea pig’s respiration produced the same amount of heat for a given amount of carbon dioxide. They concluded therefore that the heat production of animal respiration was due to combustion of carbon (from food) within the animal, and that respiration was in fact slow combustion. From this result they had the audacity to claim that a vital living process was in fact a simple chemical reaction. And they were right – well, partly.

Priestley had again been working on similar lines. He had shown that candles and mice lasted approximately five times longer in a jar of oxygen than in a jar of ordinary air. This is because ordinary air consists of one fifth oxygen and four fifths nitrogen, a gas which does not support life. Priestley said of oxgyen (or rather, as he called it, dephlogisticated air):

‘It is the ingredient in the atmospheric air that enables it to support combustion and animal life. By means of it most intense heat may be produced; and in the purest of it animals may live nearly five times as long as in an equal quantity of atmospheric air. In respiration part of this air, passing the membranes of the lungs, unites with the blood and imparts to it its florid colour, while the remainder, uniting with phlogiston exhaled from venous blood, forms mixed air.’

But if all the animals of the world are continually consuming large amounts of oxygen, why doesn’t the oxygen in the atmosphere run out, as it does in the jar? Priestley discovered that plants produced large amounts of oxygen when a light was shone on them, and went on to suggest that all the oxygen used by the animals of the world is produced by plants. This suggestion is more or less correct, although the photosynthetic bacteria and algae of the sea (also now classified as plants) contribute as well to the production of oxygen, and it would take over two thousand years for the atmospheric oxygen to run out if all plants stopped producing oxygen. So both the food we eat and the oxygen we breathe come ultimately from plants; this means all energy is derived from plants, who in turn get their energy from the sun.

But if animal respiration was a type of combustion, where within the animal did it occur? Lavoisier and Laplace believed it happened in the lungs. They thought that carbon (and hydrogen) derived from food was brought to the lungs by the blood, and was burnt there with the breathed-in oxygen to produce the waste products of carbon dioxide (and water) then breathed out; and heat, which was absorbed by the blood and distributed to the rest of the body. Their belief that respiration was the combustion of food using oxygen was correct, but they were wrong in thinking that this combustion occurred in the lungs. Their view prevailed for fifty years, although Lagrange, the famous French mathematician, argued that the combustion could not occur solely in the lungs because if all the heat were released there they would be burnt to a cinder. He postulated that oxygen was taken up by the blood and the combustion of food occurred within the blood. This theory was very influential and competed with that of Lavoisier and Laplace. But in 1850, it was found that a frog muscle, separated from the body, still takes up oxygen liberating carbon dioxide; subsequently it was shown that the liver, kidneys, brain and all the body’s other tissues do the same. In the 1870s, the role of blood was demonstrated to be solely the transport of oxygen from the lungs to the tissues, where respiration occurred within the cells, the blood then carrying back the carbon dioxide generated to the lungs. The colour change of blood, from blue-back to red on passing through the lungs, was due to a single component of blood, haemoglobin, which picked up oxygen. Haemoglobin carried oxygen in the blood: it picked up oxygen in the lungs (changing from blue to red), then carried it to the tissues, where it released the oxygen (changing back from red to blue). Thus respiration (or combustion) was occurring not in the lungs but all over the body.

But it was still not clear what relations, if any, respiration and its associated heat production had to life and its processes such as movement, work and thinking. Lavoisier and Séguin, a co-worker, had shown (using Séguin as the experimental subject) that respiration increased during work, after a meal, in the cold, and in deep thought. Thus, there appeared to be a relation between respiration and physiological work, but it was hard to imagine how oxygen consumption or heat production could cause the movement of an arm, let alone the thinking of great thoughts. To bridge that conceptual gap required the imagining of something entirely new, and that something was ‘energy’.

THE VITAL FORCE

The collapse of the four elements theory opened up a cornucopia of matter. If ‘air’ was a mixture of different gases, ‘water’ was a combination of hydrogen and oxygen and ‘fire’ was not an element at all, then what on earth was ‘earth’? The science of chemistry, newly constituted and emboldened at the start of the nineteenth century, was salivating at the prospect of dividing ‘earth’ into thousands of different ‘species’. The concept of species and family had been successfully used by Linnaeus in the eighteenth century to bring order to biological taxonomy, but what were the building blocks of matter and how were they to be classified?

The theory of the elements was recast by Lavoisier, so that there were at least thirty different elements (now known to be about a hundred), existing as elementary, indivisible ‘atoms’ (proposed by Dalton in 1808) and combined in fixed ratios to form more or less stable ‘molecules’. Chemists divided their task between the analysis of inorganic and organic (or ‘organized’) matter, the latter being the constituents or products of living organisms. The alchemists had treated organic matter as if it were a single substance or a small number of elements, for example they had treated distillates of egg or urine as single substances. The chemists set about analysing the many components of egg and urine, using new methods of organic analysis. Lavoisier had pioneered such analysis by burning organic compounds in jars of oxygen and collecting the carbon as carbon dioxide and hydrogen as water. By quantifying the amount of carbon (C), hydrogen (H), and oxygen (O), a formula of the compound could now be written down; starch was, for example, thought to be C

H

O

. This formula was mistaken, and arose from the misconception that water was HO rather than H

O. But these methods were rapidly improved and applied with great enthusiasm by several German chemists, in particular Liebig and Wöhler. In 1835, Wöhler wrote: ‘Organic chemistry appears to me like a primeval forest of the tropics, full of the most remarkable things’. These first optimistic biological chemists did not, however, comprehend the full complexity and extent of their new field. It is now thought that there may be roughly five million different organic compounds in the human body and these compounds may be organized in an almost infinite number of different ways.

Nineteenth-century Germany, although not yet united, had become the major centre for scientific and technological innovation. Perhaps partly in reaction to the rise of science and industrialism, the Romantic movement developed in late-eighteenth-century Germany producing a scientific philosophy known as Naturphilosophie. This bizarre hybrid of Romantic philosophy and science contributed to a resurgence of interest in the vital force and the relationships between all forces.

Justus von Liebig (1803–1873) dominated German chemistry and biochemistry in the nineteenth century, sometimes to the detriment of biology. The son of a dealer in drugs, dyes, oils, and chemicals, von Liebig gained an interest in chemistry assisting his father. But he did badly at school and was derided when he suggested a career as a chemist. He learned to make explosives from a travelling entertainer, terminating an apprenticeship in pharmacy when he accidentally blew up the shop. His father packed him off to university to study chemistry but he was soon arrested and sent home after becoming too involved in student politics. Somehow he eventually earned his doctorate and went to work in Paris with one of the best French chemists of the time, Joseph Gay-Lussac. In the 1820s he took a position at a small German university at Giessen, and over the next twenty-five years produced a veritable mountain of chemical data.

However, von Liebig did not produce this data himself, rather he invented the research group as a quasi-industrial means of producing scientific results. Taking over an unused barracks as a chemical laboratory, he staffed it with junior scientists as lieutenants, students as foot soldiers and with himself as the distant but all-powerful general. This model of the research group was so successful in producing the large volumes of research required in the industrial world that it was widely adopted and remains the main means of producing scientific research today. This is in strong contrast to the pre-industrial system of the individual scientist thinking up experiments and carrying them out himself, with or without assistance. Von Liebig was both arrogant and argumentative and had a number of angry disputes with other scientists. His success gave him considerable power, through his control over scientific journals, appointments, and societies. The parallels with science today are unavoidable. It is dominated by a relatively small number of politicians of science who control the boards of scientific societies, journals, conferences, grant-giving bodies, and appointment boards. Success in a scientific career still depends to a certain degree on gaining the patronage of these politician-scientists.

Von Liebig started the prodigious task of analysing the millions of different combinations of elements – molecules – that make up a human being. Some kind of order was brought to this chaos by distinguishing three main types of molecule: carbohydrates, fats, and proteins. At first it was thought that these ‘organic’ molecules could only be produced by living organisms, using some kind of vital force. But in 1828 Friedrich Wöhler, a friend and colleague of von Liebig, found that he could chemically synthesize urea (an important component of urine) without any living processes being involved. Ultimately, this would lead to the melting of the boundary between the living and the non-living, but not yet.

Although von Liebig showed that living organisms were constructed from a large number of organic chemicals, he believed that a ‘vital force’ was required to prevent these complex chemicals from spontaneously breaking down. He came to this conclusion because, in the absence of life, they did tend to break down, either by oxidation (combination with oxygen as in burning), putrefaction (as in flesh after death), or fermentation (conversion of sugar to alcohol). Von Liebig’s concept of vital force was similar to that of a physical force such as gravity or the electric force, but was only present in living organisms. Within the living body, this vital force opposed the action of the chemical forces (causing oxidation, putrefaction and fermentation), thus preventing the decay of the body so evident after death. Von Liebig also claimed that the vital force caused muscle contraction because he thought there could be no other way to account for the control of muscle by mind. When a muscle contracted, some of the vital force was used up to power the contraction. Consequently, immediately after the contraction, there was less vital force to oppose the decay (oxidation) of chemicals in the muscle, which therefore speeded up with an associated increase in respiration. The vital force acted as a brake on the chemical forces and when it was consumed by muscle contraction, the chemical forces speeded up. This is akin to the famous story of Peter, the little Dutch boy, sticking his finger in the leaking dam, trying to prevent the sea washing away the fields and town (just as the vital force prevented the chemical forces from eroding the body). This erroneous interpretation was used to explain Lavoisier and Séguin’s important discovery that respiration (the process of consuming oxygen to produce carbon dioxide and heat) greatly increased when a human or animal was working or exercising. Although von Liebig’s conception of the vital force was a form of vitalism, in the tradition of Aristotle, Paracelsus, and Stahl, the concept was more mechanistic in its appeal to Newtonian forces and foreshadows the concept of energy, formulated in the mid-nineteenth century.

Von Liebig’s belief that everything could be explained by chemistry and the vital force was opposed by Theodor Schwann (1810–1882). This clash proved catastrophic for the sensitive and as yet unestablished Schwann. Schwann’s productive work lasted just four years (1834– 1838), while he was still only in his twenties, but it was enough to spark a reorganization of biology almost as fundamental as that of Lavoisier’s of chemistry. Schwann’s first venture was to isolate a muscle from a frog and measure the force produced by the contracting muscle when it was held at different lengths or pulled against different weights. He found the muscle contracted with the greatest force when it was at the length that it was naturally found in the body. These experiments were seen as sensational in Germany, because for the very first time a vital process supposedly mediated by a vital force was treated and quantified in the same way as an ordinary physical force. It was now possible to give a physical account of vital processes, or reduce them to physical forces. This approach, however, did not please von Liebig and other champions of the vital force. Indeed Mayer later used Schwann’s experiment specifically to disprove von Liebig’s account of muscle contraction.

Schwann’s next achievement was the isolation of an enzyme which he called pepsin from the digestive juices. An enzyme is a biological substance present in small quantities which promotes a chemical reaction without being itself converted by the reaction. But ‘enzyme’ is a twentieth-century notion, in the nineteenth century they were known as ‘ferments’. For the alchemists, a ferment was a small quantity of active substance which when added to a passive substance could transform it into an active one similar to the ferment. For example, fire was the ferment converting flammable substances into flame and the philosopher’s stone was the ferment transmuting base metals into gold. Fermentation is the process responsible for the leavening of dough producing bread and for converting grapes into alcohol, making wine. This apparently magical transformation had been recognized since antiquity, but how exactly this happened was unclear, although it was known to require a ferment – yeast. Having discovered a ferment in digestive juice, Schwann concluded that digestion was a kind of fermentation. Von Liebig and the other chemists considered digestion, on the other hand, as a purely chemical process due to the action of acids on food. So when Schwann published his findings in von Liebig’s journal, von Liebig added a rather sceptical note to his paper.

Schwann then turned his attention to the nature of fermentation itself: one of the central scientific and technological problems of the nineteenth century. Von Liebig and the chemists believed fermentation was purely chemical and did not involve any biological organisms or processes. Schwann and two other researchers independently discovered that fermentation was a biological process caused by a fungus – yeast – the cells of which could be viewed through a microscope and could be destroyed by boiling. Schwann also showed that the putrefaction of meat was biologically mediated too, it could be slowed by heating and sealing the meat. These biological breakthroughs incensed the chemists who soon got their revenge. In the meantime, Schwann embarked on a microscopic study of the role of cells in animal development and in biology generally. The resulting ‘cell theory’ published in 1839 revolutionized how the body was viewed.

Since the theory of the four humours, the important components of the body had been thought to be the fluids and airs: the blood, phlegm, bile, urine, semen, cerebral-spinal fluid and pneuma. The important locations inside the body were the cavities (of heart, lungs, brain, guts, and blood vessels) where life was manifested in the turbulent motions of fluids and airs. The solid parts of the body (the ‘flesh’) were regarded as largely structural, perhaps because their very solidity and lack of motion argued against any involvement in change; therefore it was hard to conceive how they might be involved in the vital processes. Schwann changed all that, showing that the tissues were composed of cells and it was within the cells that most vital processes were generated. The cells were not static structures: they had a life of their own. They grew, reproduced, changed into different forms and died. Most importantly the power to cause change was located within the cells themselves, not their surroundings. Schwann called this power ‘metabolism’, from the Greek word for change. This ‘intracellular metabolism’ was responsible for fermentation by yeast and for respiration and heat production by all cells. If the secrets of life and energy were to be found, science would now have to follow the trail into the cell rather than pursuing phantom airs and vital forces. And this would require entirely new concepts and methods.

Cells were first seen by Robert Hooke in the early days of microscopes. But Hooke had only seen the large woody cells of plants. It was much harder to see animal cells, because they were smaller and their walls (membranes) were almost invisible. So the structure of animal tissue was unclear, and it had mostly been described in terms of fibres and ‘globules’ of unknown function. Schwann benefited from a great improvement in microscope optics, using this to show that not only were cells everywhere in the body, but that they were the body’s organizing principle. All cells in the body were derived from embryonic cells which divided and differentiated to form the hundreds of different types of cell making up the organism. If there was a vital principle in the body, Schwann believed that it had to be located in the cells, because all the essential processes, such as reproduction, growth, and respiration, were located in individual cells. Doubting the possibility of a vital force, Schwann thought all the properties of cells could be explained in terms of physical and chemical forces. He also believed that living processes within cells could be explained in terms of the physical structures and movements of the molecules. This was an important and influential insight which foreshadowed the spectacular explosion of cellular and molecular biology in the twentieth century. Though intensely religious, Schwann argued persuasively that the concept of a vital force was completely unnecessary, denying God’s achievement in originally producing the Universe and its physical forces: these were all that was necessary to create life.

Schwann did not have the whole answer to how cells created life, but he had found important clues in his notion of ‘metabolism’ and his discovery that digestion was partly due to pepsin. Pepsin was thought to be a ‘ferment’, but at the end of the nineteenth century it was found that ferments consisted of single biological molecules, now called ‘enzymes’. Enzymes are the magic molecules inside cells that actually cause the ‘change’ of metabolism. Enzymes are made from protein. They act on the chemicals and structures inside and outside the cell changing them from one form to another. For example, pepsin cuts other proteins into pieces without itself being cut up. Each type of enzyme can cause only one type of change but there are roughly 10,000 different types of enzyme in a cell. These enzymes are the alchemists of the cell. But each enzyme molecule can be regarded as a minute, exquisitely designed, molecular machine. Machines, because they are designed structures, performing specific tasks and transforming things by physically interacting with them; and molecular, because they consist of single molecules. Enzymes and the other molecular machines of the cell are the engines of life.

Enzymes were first discovered within yeast, as the word itself reflects – ‘enzyme’ means ‘in yeast’. Although Schwann and others had shown that fermentation was caused by yeast cells, this discovery was ridiculed by von Liebig and the chemists and replaced by von Liebig’s own nebulous chemical theory. So, the biological theory of fermentation (that it is caused by living cells rather than dead chemicals) had to be re-established later in the century by Louis Pasteur. Pasteur was unable, however, to isolate from yeast cells a ‘ferment’ which could cause the fermentation of grape juice into alcohol, in the absence of live cells. Thus it was unclear whether fermentation was a truly vital process, only occurring within living cells. This was crucial because if the sub-processes of life such as the transformation of chemicals, could not occur in isolation from a living cell, then this implied that there was indeed some vital force involved. In more practical terms, it also meant that science would never penetrate far into the cell, because the individual processes could not be studied in isolation. It was left to Buchner at the very end of the century to at last successfully grind up yeast cells, and isolate something (a bunch of enzymes) that could cause fermentation in the absence of living yeast cells. It is this event that marks the true beginning of Biochemistry, in part because it destroyed the concept of the vital force, but mainly because science had finally broken into the cell and was able to study the processes of life at the molecular level.

Schwann had opposed von Liebig and the other chemists’ views on virtually everything: the role of biology rather than chemistry in digestion, fermentation, putrefaction, metabolism, tissue structure, muscle function and the vital force. The chemists, clearly rattled by this upstart, went onto the attack, writing a satirical article on the views of the ‘biologists’ on fermentation. This article, drafted by Wöhler and made more vitriolic by von Liebig, ridiculed the cell theory of Schwann and others, scathingly describing it in terms of anthropomorphized cells shaped like distilling flasks with big mouths and stomachs, gulping down grape juice and belching out gases and alcohol. Schwann’s credibility was destroyed, he lost his job and was prevented from obtaining another academic post in Germany. He escaped into exile in Belgium, with a post in the Catholic University of Louvain, where his time was filled teaching anatomy. He never did any significant biological research again, keeping his head well below the parapet, and the chemists held the field once again in Germany. However, the experiments and book Schwann had produced in his four years of active research proved immensely influential, eventually leading to the demise of von Liebig’s ascendancy and the transformation of biology. Von Liebig publicly battled on against Pasteur, but after thirty years of denial eventually had to admit that he had been mistaken about the biological basis of fermentation. The stresses of the struggle and eventual defeat may well have contributed to his death soon afterwards. The idea of the vital force died with him, later to be reborn in the transmuted form of ‘Energy’.

We have now learnt our ‘chemistry’. We know life is not created by spirits sucked in from the air to push and pull the body’s levers; but rather an element of air, oxygen, is combined with molecules of food within the cells of the body, producing something then able to animate our bodies and minds. The stage is now set for the discovery of energy itself.

THE BIRTH OF ENERGY

The modern scientific concept of energy was an invention of the mid-nineteenth century. ‘Energy’ is a child of the industrial revolution: its father a thrusting steam engine; its mother, the human body itself, in all its gory physicality; and its ancestors the ethereal spirits of breath and air. The evolution of this concept was aided by an eclectic group of engineers, physicians, mathematicians, physiologists and physicists, with a strong supporting cast of soldiers, sailors and, inevitably, accountants. Today, the scientific concept of energy has a harsh façade of cold forces and austere maths, but its core is much softer and more appealing, reflecting its biological origins in vital forces and wild spirits.

The physical heritage of energy begins with Watt’s invention of the steam engine in the eighteenth century. A steam engine produces work (movement against a force) from heat, something never before possible. The question is how? Is heat somehow converted into work or does the flow of heat from hot to cold drive work as the flow of water in a stream drives a water-mill? Sadi Carnot (1796–1832) thought the latter was true but was only half right. Carnot’s father was a Minister of War in Napoleon’s government and Sadi fought in the defence of Paris in 1814. The total defeat of Napoleon’s armies and France’s ignoble subjugation turned Carnot’s thoughts towards one source of England’s growing power: James Watt’s steam engine. The engine seemed to promise limitless power derived from hot air and steam alone but the elaborate contraptions of the early nineteenth century did not always deliver what was promised. Carnot wanted to improve the efficiency of steam engines but there was still no good theory of how they actually worked. So Carnot produced one, based on Lavoisier’s conception of heat. Lavoisier had disposed of the phlogiston theory of combustion but had replaced it with something rather similar: the caloric theory of heat. According to Lavoisier, heat was a substance, a massless fluid called ‘caloric’, which he considered one of the elements, like oxygen or phosphorus. This caloric theory was mistaken but its legacy still remains in our unit of heat energy: the ‘calorie’. Carnot thought if heat was an indestructible fluid, then steam engines must be driven by the flow of heat from a hot source (the boiler) to a cold sink (the condenser), just as a mill-wheel is impelled by the flow of water. His important insight was that there had to be a large temperature difference to cause the heat to flow and that there was a quantitative relation between this heat flow and the power output of the engine, which could then be used to predict the efficiency of conversion of coal into work.

Carnot’s theory was, however, based on Lavoisier’s mistake, that heat was an indestructible substance or element. This mistake was revealed by James Joule (1818–1889), a rich brewer from Manchester. In the brewery workshops, Joule measured the heat produced by passing electricity through water. His results showed electricity was being converted into heat, which was impossible if heat and electricity were two indestructible fluids. The fellows of the Royal Society were unimpressed by his findings, so Joule went back to the workshop and started meticulously measuring the small amount of heat generated by turning paddles in water. From these experiments it appeared that work could be quantitatively converted into heat. The cautious Royal Society again rejected Joule’s findings as impossible. Joule became so obsessed with proving his case that when on honeymoon in Switzerland, ignoring the romantic situation and scenery, he spent much of the time dragging his wife up and down a waterfall, trying to measure the temperature difference of the water between the top and bottom – an impossible task. Slowly, other scientists started paying attention to Joule; if work could be converted into heat, then heat could not be conserved, and perhaps heat could be converted back into work.

Joule’s revolutionary finding disturbed one particular scientist, the precocious William Thomson, later Lord Kelvin (1824–1907). Kelvin had joined Glasgow University at ten, was a professor by 22 and went on to a meteoric career in theoretical physics. He also had a strong practical streak, and made a fortune from his invention of telegraphy. Kelvin heard Joule describe his discoveries at a scientific meeting in Oxford in 1847 and afterwards he struggled with his inability to reconcile Joule’s finding that heat and work were incontrovertible with Carnot’s assumption that heat was indestructible but that the flow of heat drove work. The resolution of this conundrum produced two new laws for the Universe to ‘obey’: the First and Second Laws of Thermodynamics, joint products of the minds of Joule, Mayer, Kelvin, Helmholtz and Clausius. The First Law stated that heat and work (and other forms of energy) were incontrovertible but energy itself was indestructible. The infamous Second Law of Thermodynamics implied that although energy could not be destroyed in any conversion between its forms, it was inevitably ‘dissipated’ into other forms (mainly heat) less able to do work. Thus although work could be fully converted into heat, heat could not be completely converted into work, because, as Carnot had indicated, part of the heat had to be released to the cold sink in order that the flow of heat could continue and this heat could not then be converted to work. The implication of the Second Law was that all energy was continually running down or ‘dissipating’ into heat. Therefore the clockwork Universe must eventually run down unless there was something – or someone – outside the Universe to wind it back up again.

The First Law showed that heat could not be indestructible and this led to the resurrection of an old theory that heat (and perhaps all forms of energy) were hidden forms of motion. In hot water, water molecules move around very rapidly, while in cold water the molecules move slowly: when hot and cold water are mixed, the rapidly moving molecules of the hot collide with the slow-moving molecules of the cold, slowing the rapid molecules and speeding up the slow molecules which results in lukewarm water. Thus, the transfer of heat is really a transfer of motion. The exchange between all types of physical force in a common currency of energy gave a great unity to late-nineteenth-century science; a unity missing in the eighteenth century when electricity, magnetism, heat, light and work were all different and discussed in different terms. In the nineteenth century, because these apparently different physical forms could be interconverted they came to be regarded as different forms or manifestations of one thing: energy. But energy was not a type of matter but rather the motion or arrangement of matter. This concept of energy gave a new boost to the hopes of mechanists, who thought they might finally be able to describe everything in the Universe in terms of matter in motion. It has been argued that the origin of this energy concept was partly due to new concepts in accountancy accompanying the rise of industrialization: it is certainly true that energy acted as a new currency within physics keeping track of mechanical transactions. Prior to the 1850s ‘energy’ did not exist as a useful concept in science, afterwards it became the central concept. However, the word ‘energy’ entered the English language in the sixteenth century, meaning roughly ‘vigour of expression’, and later ‘vigour of activity’. Originally the word was derived from Aristotle’s term energeia, meaning actuality/activity; this in turn is derived from the Greek en for in or at and ergon for work. Today the word ‘energy’ has a rather schizoid existence, meaning something technical and quantifiable to scientists, but having a variety of metaphorical meanings in the wider community.

The scientific concept of energy did not arise purely from physics, but also at the same time from biology. Indeed the principle of energy conservation was simultaneously discovered by about twelve different scientists but was first formulated by the physicians Mayer and Helmholtz with reference to the forces of life. Robert Mayer (1814– 1878) was a German physician with an unlucky life. A mediocre student, he was arrested and expelled for joining a secret society. He eventually graduated and joined a ship bound for the East Indies as the ship’s doctor. At that time doctors still followed Hippocrates and Galen’s advice to bleed patients for a variety of maladies. While bleeding sailors in the East Indies, Mayer was alarmed to find that blood from the veins was much redder than usual, almost like arterial blood. At first, he worried he was puncturing arteries by mistake but local doctors assured him it was normal for venous blood to be redder in the tropics than in the cold north. This set Mayer thinking. He knew that Lavoisier had proposed respiration functioned to produce heat for the body and he also knew that the change from red to blue blood from arteries to veins was due to the removal of oxygen from the blood for respiration. Thus redder blood in the veins of a sailor in the tropics might be due to less respiration and heat production, which would make sense since the body needed to produce less heat in the tropics than the cold north. He also knew Lavoisier had shown men doing hard work respired more but had not given a convincing explanation of this important finding. Mayer proposed that fuel, heat and work were interconvertible: that it was possible to convert one into the others. Thus work done by men could be produced from heat (as in a steam engine) and this heat could in turn be produced by respiration (the burning of food). More work required more heat and more respiration as Lavoisier and Séguin had found experimentally. This reasoning, although partly wrong, was definitely getting closer to the secret of the energy of life.

When Mayer got back to Germany he wrote up his ideas in a scientific paper, but his thinking was muddled and the paper was rejected. On a second attempt he sent the paper to von Liebig, who published it in 1842. However, when von Liebig published soon after a related theory, Mayer accused him of plagiarism. As Schwann would have agreed, it was not wise to oppose the powerful von Liebig. Mayer then got into even deeper water when he started a priority dispute with Joule as to who had first thought of the conservation of energy. But Mayer lost both arguments due to his unestablished position. The ‘Joule’ is now the standard scientific unit of energy and the ‘Kelvin’ the standard unit of temperature, while Mayer’s name is nowhere to be seen in the virtual world of scientific units. Understandably, he became depressed, suffering a mental breakdown and attempting suicide.

Mayer’s ideas on the conservation of forces were not sufficiently general and quantitative to convince most scientists that something important had been discovered. This situation was dramatically changed by the great German physiologist Hermann von Helmholtz (1821–94), who in 1847 at twenty-six published his famous paper on the conservation of force. Helmholtz gave an exact quantitative definition of energy, explaining how the conservation of energy followed naturally from the known laws of physics. Using these principles, he suggested that heat and work generated by animals must derive entirely from the burning of food in respiration. Although Helmholtz was strongly sympathetic to von Liebig’s work, he pointed out that the vital force was incompatible with the conservation of energy (because the vital force could be converted into physical forces but not vice versa), and must thus be discarded by the new science of energy. Helmholtz was a founding member of a school of German physiologists (known variously as the Helmholtz, Berlin or 1847 School of Physiologists) who sought to explain all biological processes in terms of known physical, rather than vital, forces.

According to Helmholtz’s version of the conservation of energy, there was a single, indestructible and infinitely transformable energy basic to all nature. This ‘Energy’ was more fundamental to the Universe than matter and force, as the overarching theory of the conservation of energy constrained the manifest forms of matter and motion. Energy was well on its way to replacing God. The good news of the First Law was that the Universe was now a vast reservoir of protean energy awaiting conversion into work. The bad news of the Second Law was that this conversion was taxed by the dissipation of some energy into heat. Although all forms of energy were equal, some forms were more equal than others.

The discovery of the conservation of energy was partly due to the recognition that any quest to build a perpetual-motion machine was doomed. In the eighteenth century the French Academy of Sciences had set up a commission to examine proposals for building such a mythical machine: although many tried (including the young Mayer) all had failed. Such a machine would produce motion and work out of nothing. It would be an ‘unmoved mover’, something that Aristotle had associated with God alone. The recognition that perpetual motion was impossible led to the idea that all motion must arise from some prior, actual or potential motion: no change without a prior change. Therefore the whole history of the Universe was locked into one single causal web. Helmholtz criticized von Liebig’s concept of the vital force powering muscle contraction because the concept allowed the possibility of a perpetual motion machine which he considered impossible. But if energy conservation prevented the vital force from acting, some thought it would also prevent God interfering with the material world. Lord Kelvin magnanimously gave God a special dispensation to create or destroy energy. But others were less generous, relegating Him to the role of creating a fixed amount of energy at the start of the Universe and then sitting impotently on the sidelines as the consequences of His creation unfolded. Surprisingly some physicists now believe that the net amount of energy at the beginning of the Universe was zero, so perhaps it was God who was lacking in generosity.

The ancient Greeks said Prometheus had stolen fire from the gods, given it to mankind and with it part of their divine knowledge and power. Now, through Helmholtz and the others, mankind had acquired the concept of energy itself, and with it a greatly increased power for good or evil. If this concept of energy could be used to understand the secret of life and death, then perhaps death itself could be conquered and humans might at last become immortal gods.

The relation between respiratory heat production and muscle work and in general the coupling between respiration and energy use in the body still remained obscure throughout the nineteenth century. It was gradually established that respiration – oxygen consumption, carbon dioxide and heat production – occurred within the tissue cells, rather than in the lungs or blood. It was thus suggested that muscles might work as biological steam engines using the heat generated by respiration to drive contraction. But by the end of the century, it was realized that this would not work, as the Second Law of Thermodynamics indicates that heat is a very inefficient source of work unless the temperature difference between machine and environment is very high. At normal physiological temperatures a heat engine would therefore be extremely inefficient, generating very little work for the amount of food burnt. The only realistic way of using respiration to drive muscle contraction was to bypass heat production and pass the energy released by respiration through some intermediate energy store to muscle contraction, without releasing the energy as heat. But it took another century to work out how this feat was achieved.

The historical trail we have followed in pursuit of the secrets of life and energy has branched many times as the questions have multiplied, and the answers have led us off into territory ever more obscure and abstruse. To summarize, before pressing on in the next chapters to the summit of present understanding of body energy: we started by looking at the general modes of biological explanation in early cultures where energy and life were not distinguished from each other and where all movement and change were attributed to anthropomorphic souls, gods or spirits. Energy, enthusiasm and life were given by the gods and equally spirit and health could be taken away by the gods or devils. Mechanisms were not considered, because ‘mechanism’ was not involved. In ancient Greece and Rome the role of gods and souls gradually diminished. Energy came in the form of pneuma, a spirit of the air, circulating in the body and providing the ‘go’ of life. In Renaissance and Enlightenment Europe, spurred on by advances in technology, gods and souls were ejected from science and replaced by cold mechanics. Crucially, hypotheses were now tested by experiment rather than rational plausibility and this was aided by the injection of mathematics into scientific theories and experiments. Pneuma and spirits were replaced by ‘forces’ and ‘laws’. A component of the air, oxygen, was found to be essential to life and consumed inside the living body in the process of burning digested food, resulting in the production of body heat. This process of respiration was eventually found to be located in the cells of the body and carried out by enzymes, the molecular machines of the cell. The various forces of nature were found convertible between each other and into movement and heat and, thus, were united in the common concept of energy, the universal source of all movement and change. The body then became an energy converter (or engine), channelling the energy released by burning food into movement and thought, but how exactly this was effected was unknown.

The appealing idea of the history of science as a continuous ascent towards the pinnacle of modern truth, is, of course, anathema to most historians. They point out this view of history arises from taking the contemporary truth and weaving a narrative towards it – carefully selecting from the past. My brief historical overview gives little idea of how scientists really thought and operated in the past. It does, however, give us a sense of where our present-day concept of energy came from and how it evolved; and now we must follow it right up to the constantly moving present, where a number of shocks await.

Chapter 3 ENERGY ITSELF (#ulink_3314fb49-301c-543b-a04e-55e82c544977)

WHAT IS ENERGY?

I taught bioenergetics (the science of body energy) in Cambridge for many years before I realized that I did not, myself, understand what energy was. Tutorials are meant to be cosy but fiercely intellectual chats between a teacher and one or two students. However, teachers can often rattle on without knowing what they are talking about. One fine day I discovered that was true of me and energy. Part of the problem with energy is that it is an abstract idea, so that one answer to the question ‘What is energy?’ is ‘A concept existing in a scientist’s head’. But another, more subtle problem is how the concept of energy has evolved historically, so that many layers of meaning, not always consistent, have been superimposed on the words and symbols. So take heart, if at first you do not understand the meaning of energy, it will not necessarily disqualify you from either 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 and cooking up thoughts in the brain like some benign ghost dashing around pulling the levers of body and mind. The modern idea of energy is more like that of money. Money gives the capacity to buy things, coming in many forms, such as coins, notes, cheques, credit cards, bank accounts, bonds, gold etc. It can be used to buy many sorts of things, such as hats, houses and horses. Money allows the exchange of these things at a fixed rate, so that I can, for example, exchange a fixed quantity of coins for one horse. ‘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 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, so that, for example, a certain amount of heating requires the expenditure of a certain amount of chemical energy. One important difference between money and energy is, however, that money and monetary value are not exactly conserved. You may pay £100,000 for a house one year, selling it for £110,000 or £90,000 the next year without having altered or improved the house and this £10,000 does not suddenly appear or disappear from elsewhere in the economy. You can burn a £10 note and money simply disappears in smoke. Neither money nor monetary value is absolutely conserved: there is no Economic equivalent to the First Law in Thermodynamics. If there was, Economics would be easier but we might also be poorer. Energy is strictly conserved, as expressed by the First Law of Thermodynamics, which states that during any change of any sort the total amount of energy in the Universe stays the same. If you use one hundred units of energy to raise a rock one hundred feet in the air, on your return a year later lowering the rock to the ground one hundred units of energy will be released. It may not be released in wholly desirable ways – the energy may be released as heat, sound or work depending on how the rock is lowered, but when the energy released is added up the total will be one hundred units.

Money or monetary value is an abstract concept since it can reside in very different objects, such as coins or a bank account. Energy is similarly abstract since it is contained in many different types of thing, while not actually being them; energy rather is their capacity to produce movement or change. Energy is not in addition to the things themselves: it is rather as if an accountant were examining the situation, assessing the capacity for movement or change. For example if a rock is balanced at the edge of a chasm, it is possible to work out that if it were tipped into the chasm so much energy would be released as movement, noise, heat etc. Before the rock is moved, this energy does not reside in the rock or chasm any more than monetary value resides in coins or horses: this is because energy or monetary value are not tenuous forms of matter, but rather ways of quantifying the potential for change. Energy quantifies the capacity for movement or physical change within any particular situation.

Energy is like money in another way. Money does not determine how or when it 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 or not. The presence of a million dollars does not determine how or when it will be spent but does mean that x number of houses, y amount of strawberries or z number of horses could be bought. Similarly the presence of one million units of energy does not determine how or when the energy will be used, but it does mean that x amount of heat, y amount of movement or z amount of electricity could be produced.

The great American physicist Richard Feynman warned us of the abstract nature of energy in his famous 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, using the figures for predictions, but have no idea what it is in itself. Energy seems just an abstract accounting concept like money quantifying the amount of movement that could be produced by a particular system. How boring! Yet, according to physics, energy is perhaps the most fundamental property of the Universe. Energy is the one constant conserved through all change. Everything can be created from or dissolved into energy, including even matter itself: which is demonstrated by atomic explosions and Einstein’s famous equation E = mc

. In this rather abstract scheme of things, 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? Newton said all movement or change is brought about by forces. In our lives we experience only two types: gravitation and contact forces. Gravitational force pulls everything towards the earth’s centre 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. Gravitational force exists because every bit of matter is attracted to every other bit, causing them to accelerate towards each other. All the contact forces are different manifestations of one immensely powerful force: the electric force. Electric force is the force of attraction or repulsion between all charged matter. Gravitational force and electric force account for virtually all movement and change in our universe. There are two other forces known: strong nuclear force and weak nuclear force but their range of action is so small, they can only be observed by breaking open the nucleus of an atom. Thus nuclear forces have no apparent effect either on biology or our everyday lives.