by Oliver Sacks
Between them, Bohr and Moseley had restored arithmetic to me, provided the essential, transparent arithmetic of the periodic table which had been intimated, though only in a muddy way, by atomic weights. The character and identity of the elements, much of it, anyhow, could now be inferred from their atomic numbers, which no longer just indicated nuclear charge but stood for the very architecture of each atom. It was all divinely beautiful, logical, simple, economical, God’s abacus at work.
What made metals metallic? Electronic structure explained why the metallic state seemed to be fundamental, so different in character from any other. Some of the mechanical properties of metals, their high densities and melting points, could now be explained in terms of the tightness with which electrons were bound to the nucleus. A very tightly bound atom, with a high ‘binding energy,’ seemed to go with unusual hardness and density, and high melting point. Thus it was that my favorite metals – tantalum, tungsten, rhenium, osmium: the filament metals – had the highest binding energies of any of the elements. (So there was, I was pleased to learn, an atomic justification for their exceptional qualities – and for my own preference.) The conductivity of metals was ascribed to a ‘gas’ of free and mobile electrons, easily detached from their parent atoms – this explained why an electric field could draw a current of mobile electrons through a wire. Such an ocean of free electrons, on the surface of a metal, could also explain its special luster, for oscillating violently with the impact of light, these would scatter or reflect any light back on its own path. The electron-gas theory carried the further implication that under extreme conditions of temperature and pressure, all the nonmetallic elements, all matter, could be brought into a metallic state. This had already been achieved with phosphorus in the 1920s, and it was predicted, in the 1930s, that at pressures in excess of a million atmospheres it might be achieved with hydrogen, too – there might be metallic hydrogen, it was speculated, at the heart of gas giants like Jupiter. The idea that everything could be ‘metallized’ I found deeply satisfying.«70»
I had long been puzzled by the peculiar powers of blue or violet light, short-wavelength light, as opposed to red or long-wavelength light. This was clear in the darkroom: one could have quite a bright ruby safelight that would not fog a developing film, whereas the least hint of white light, daylight (which of course contained blue), would fog it straightaway. It was clear, too, in the lab, where chlorine, for example, could be safely mixed with hydrogen in red light, but the mixture would explode in the presence of the least white light. And it was clear with Uncle Dave’s mineral cabinet, where one could induce phosphorescence or fluorescence with blue or violet light, but not with red or orange light. Finally, there were the photoelectric cells that Uncle Abe had in his house; these could be activated by the merest pencil of blue light, but would not respond to even a flood of red light. How could a huge amount of red light be less effective than a tiny amount of blue light? It was only after I had learned something of Bohr and Planck that I realized the answer to these apparent paradoxes must lie in the quantal nature of radiation and light, and the quantal states of the atom. Light or radiation came in minimum units or quanta, the energy of which depended on their frequency. A quantum of short-wavelength light – a blue quantum, so to speak – had more energy than a red one, and a quantum of X-rays or gamma rays had far more energy still. Each type of atom or molecule – whether of a silver salt in a photographic emulsion, or of hydrogen or chlorine in the lab, or of cesium or selenium in Uncle Abe’s photocells, or of calcium sulfide or tungstate in Uncle Dave’s mineral cabinet – required a certain specific level of energy to elicit a response; and this might be achieved by even a single high-energy quantum, where it could not be evoked by a thousand low-energy ones.
As a child I thought that light had form and size, the flower-like shapes of candle flames, like unopened magnolias, the luminous polygons in my uncle’s tungsten bulbs. It was only when Uncle Abe showed me his spinthariscope and I saw the individual sparkles in this that I started to realize that light, all light, came from atoms or molecules which had first been excited and then, returning to their ground state, relinquished their excess energy as visible radiation. With a heated solid, such as a white-hot filament, energies of many wavelengths were emitted; with an incandescent vapor, such as sodium in a sodium flame, only certain very specific wavelengths were emitted. (The blue light in a candle flame which had so fascinated me as a boy, I later learned, was generated by cooling dicarbon molecules as they emitted the energy they had absorbed when heated.)
But the sun, the stars, were like no lights on earth. They were of a brilliance, a whiteness, exceeding the hottest filament lamps (some, like Sirius, were almost blue). One could infer, from the radiation energy of the sun, a surface temperature of about 6,000 degrees. No one in his youth, Uncle Abe reminded me, had any idea what could allow the enormous incandescence and energy of the sun. Incandescence was scarcely the right word, for there was no burning, no combustion, in the ordinary sense – most chemical reactions, indeed, ceased above 1,000 degrees.
Could gravitational energy, the energy generated by a gigantic mass contracting, keep the sun going? This, too, it seemed, would be wholly inadequate to account for the blazing heat and energy of the sun and stars, undimmed for billions of years. Nor was radio-activity a plausible source of energy, because radioactive elements were not present in the stars in anywhere near the needed quantities, and their output of energy was too slow and unhurryable.
It was not until 1929 that another idea was put forth: the notion that, given the prodigious temperatures and pressures of a star’s interior, atoms of light elements might fuse together to form heavier atoms – that atoms of hydrogen, as a start, could fuse to form helium; that the source of cosmic energy, in a word, was thermonuclear. Huge amounts of energy had to be pumped into light nuclei to make them fuse together, but once fusion was achieved, even more energy would be given out. This would in turn heat up and fuse other light nuclei, producing yet more energy, and this would keep the thermonuclear reaction going. The inside of the sun reaches enormous temperatures, something on the order of twenty million degrees. I found it difficult to imagine a temperature like this – a stove at this temperature (George Gamow wrote in The Birth and Death of the Sun ) would destroy everything around it for hundreds of miles.
At temperatures and pressures like this, atomic nuclei – naked, stripped of their electrons – would be rushing around at tremendous speed (the average energy of their thermal motion would be similar to that of alpha particles) and continually crashing, uncushioned, into one another, fusing to form the nuclei of heavier elements.
We must imagine the interior of the Sun [Gamow wrote] as some gigantic kind of natural alchemical laboratory where the transformation of various elements into one another takes place almost as easily as do the ordinary chemical reactions in our terrestrial laboratories.
Converting hydrogen to helium produced a vast amount of heat and light, for the mass of the helium atom was slightly less than that of four hydrogen atoms – and this small difference in mass was totally transformed into energy, in accordance with Einstein’s famous e = mc². To produce the energy generated in the sun, hundreds of millions of tons of hydrogen had to be converted to helium each second, but the sun is composed predominantly of hydrogen, and so vast is its mass that only a small fraction of it has been consumed in the earth’s lifetime. If the rate of fusion were to decline, then the sun would contract and heat up, restoring the rate of fusion; if the rate of fusion were to become too great, the sun would expand and cool down, slowing it. Thus, as Gamow put it, the sun represented ‘the most ingenious, and perhaps the only possible, type of ‘nuclear machine,’’ a self-regulating furnace in which the explosive force of nuclear fusion was perfectly balanced by the force of gravitation. The fusion of hydrogen to helium not only provided a vast amount of energy, but also created a new element in the world. And helium atoms, given enough heat, could be fused to make
heavier elements, and these elements, in turn, to make heavier elements still.
Thus, by a thrilling convergence, two ancient problems were solved at the same time: the shining of stars, and the creation of the elements. Bohr had imagined an aufbau, a building up of all the elements starting from hydrogen, as a purely theoretical construct – but such an aufbau was realized in the stars. Hydrogen, element I, was not only the fuel of the universe, it was the ultimate building block of the universe, the primordial atom, as Prout had thought back in 1815. This seemed very elegant, very satisfying, that all one needed to start with was the first, the simplest of atoms.«71»
Bohr’s atom seemed to me ineffably, transcendently beautiful – electrons spinning, trillions of times a second, spinning forever in predestined orbits, a true perpetual-motion machine made possible by the irreducibility of the quantum, and the fact that the spinning electron expended no energy, did no work.
And more complex atoms were more beautiful still, for they had dozens of electrons weaving separate paths, but organized, like tiny onions, in shells and subshells. They seemed to me not merely beautiful, these gossamer but indestructible things, but perfect in their way, as perfect as equations (which indeed could express them) in their balancing of numbers and forces and shieldings and energies. And nothing, no ordinary agency, could upset their perfections. Bohr’s atoms were surely close to Leibniz’s optimum world.
‘God thinks in numbers,’ Auntie Len used to say. ‘Numbers are the way the world is put together.’ This thought had never left me, and now it seemed to embrace the whole physical world. I had started to read a little philosophy at this point, and Leibniz, so far as I could understand him, appealed to me especially. He spoke of a ‘Divine mathematics,’ with which one could create the richest possible reality by the most economical means, and this, it now seemed to me, was everywhere apparent: in the beautiful economy by which millions of compounds could be made from a few dozen elements, and the hundred-odd elements from hydrogen itself; the economy by which the whole range of atoms was composed from two or three particles; and in the way that their stability and identity were guaranteed by the quantal numbers of the atom itself – all this was beautiful enough to be the work of God.
CHAPTER TWENTY-FIVE
The End of the Affair
It was ‘understood,’ by the time I was fourteen, that I was going to be a doctor; my parents were doctors, my brothers in medical school. My parents had been tolerant, even pleased, with my early interests in science, but now, they seemed to feel, the time for play was over. One incident stays clearly in my mind. It was 1947, a couple of summers after the war, and I was with my parents in our new Humber touring the South of France. Sitting in the back, I was talking about thallium, rattling on and on and on about it: how it was discovered, along with indium, in the 1860s, by the brilliantly colored green line in its spectrum; how some of its salts, when dissolved, could form solutions nearly five times as dense as water; how thallium indeed was the platypus of the elements, with paradoxical qualities that had caused uncertainty about its proper placement in the periodic table – soft, heavy, and fusible like lead, chemically akin to gallium and indium, but with dark oxides like those of manganese and iron, and colorless sulphates like those of sodium and potassium. Thallium salts, like silver salts, were sensitive to light – one could have a whole photography based on thallium!
The thallous ion, I continued, had great similarities to the potassium ion – similarities which were fascinating in the laboratory or factory, but utterly deadly to the organism, for, biologically almost indistinguishable from potassium, thallium would slip into all the roles and pathways of potassium, and sabotage the now-helpless organism from within. As I babbled on, gaily, narcissistically, blindly, I did not notice that my parents, in the front seat, had fallen completely silent, their faces bored, tight, and disapproving – until, after twenty minutes, they could bear it no longer, and my father burst out violently: ‘Enough about thallium!’
But it was not sudden – I did not wake up one morning and find that chemistry was dead for me; it was gradual, it stole upon me bit by bit. It happened at first, I think, without my even realizing it. It came upon me sometime in my fifteenth year that I no longer woke up with sudden excitements – ’Today I will get the Clerici solution! Today I will read about Humphry Davy and electric fish! Today I will finally understand diamagnetism, perhaps!’ I no longer seemed to get these sudden illuminations, these epiphanies, those excitements which Flaubert (whom I was now reading) called ‘erections of the mind.’ Erections of the body, yes, this was a new, exotic part of life – but those sudden raptures of the mind, those sudden landscapes of glory and illumination, seemed to have deserted or abandoned me. Or had I, in fact, abandoned them? For I was no longer going to my little lab; I only realized this when I wandered down one day and saw a light layer of dust on everything there. I had scarcely seen Uncle Dave or Uncle Abe for months, and I had ceased to carry my pocket spectroscope with me.
There had been times when I would sit in the Science Library, entranced for hours, totally oblivious to the passage of time. There were times when I seemed to see ‘lines of force’ or electrons dancing, hovering, in their orbitals, but now this half-hallucinatory power was gone too. I was less dreamy, more focused, school reports said – that, perhaps, was the impression I gave – but what I felt was wholly different; I felt that an inner world had died and been taken from me.
I often thought of Wells’s story about the door in the wall, the magic garden the little boy gets admitted to, and his subsequent exile or expulsion from it. He does not notice at first, in the press of life and outer achievement, that he has lost something, then the consciousness of this begins to grow on him, eroding and finally destroying him. Boyle had called his lab an ‘Elysium’; Hertz had spoken of physics as ‘an enchanted fairyland.’ I felt I was now outside this Elysium, that the doors of the fairyland were now closed to me, that I had been expelled from the garden of numbers, the garden of Mendeleev, the magic play realms to which I had had admittance as a boy.
With the ‘new’ quantum mechanics, developed in the mid-1920s, one could no longer see electrons as little particles in orbit, one had to see them now as waves; one could no longer speak of an electron’s position, only of its ‘wave function,’ the probability of finding it in a particular place. One could not measure its position and velocity simultaneously. An electron, it seemed, could be (in some sense) everywhere and nowhere at once. All this set my mind reeling. I had looked to chemistry, to science, to provide order and certainty, and now suddenly this was gone.«72» I found myself in a state of shock, and I was past my uncles now, and in deep water, alone.«73»
This new quantum mechanics promised to explain all of chemistry. And though I felt an exuberance at this, I felt a certain threat, too. ‘Chemistry,’ wrote Crookes, ‘will be established upon an entirely new basis…We shall be set free from the need for experiment, knowing a priori what the result of each and every experiment must be.’ I was not sure I liked the sound of this. Did this mean that chemists of the future (if they existed) would never actually need to handle a chemical; might never see the colors of vanadium salts, never smell a hydrogen selenide, never admire the form of a crystal; might live in a colorless, scentless mathematical world? This, for me, seemed an awful prospect, for I, at least, needed to smell and touch and feel, to place myself, my senses, in the middle of the perceptual world.«74»
I had dreamed of becoming a chemist, but the chemistry that really stirred me was the lovingly detailed, naturalistic, descriptive chemistry of the nineteenth century, not the new chemistry of the quantum age. Chemistry as I knew it, the chemistry I loved, was either finished or changing its character, advancing beyond me (or so I thought at the time). I felt I had come to the end of the road, the end of my road, at least, that I had taken my journey into chemistry as far as I could.
I had been living (it seems to me in retrospect) in a sort of sweet interlud
e, having left behind the horrors and fears of Braefield. I had been guided to a region of order, and a passion for science, by two very wise, affectionate, and understanding uncles. My parents had been supportive and trusting, had allowed me to put a lab together and follow my own whims. School, mercifully, had been largely indifferent to what I was doing – I did my schoolwork, and was otherwise left to my own devices. Perhaps, too, there was a biological respite, the special calm of latency.
But now all this had changed: other interests were crowding in, exciting me, seducing me, pulling me in different ways. Life had become broader, richer, in a way, but it was also shallower, too. That calm deep center, my former passion, was no longer there. Adolescence had rushed upon me, like a typhoon, buffeting me with insatiable longings. At school I had left the undemanding classics ‘side,’ and moved to the pressured science side instead. I had been spoiled, in a sense, by my two uncles, and the freedom and spontaneity of my apprenticeship. Now, at school, I was forced to sit in classes, to take notes and exams, to use textbooks that were flat, impersonal, deadly. What had been fun, delight, when I did it in my own way became an aversion, an ordeal, when I had to do it to order. What had been a holy subject for me, full of poetry, was being rendered prosaic, profane.
Was it, then, the end of chemistry? My own intellectual limitations? Adolescence? School? Was it the inevitable course, the natural history, of enthusiasm, that it burns hotly, brightly, like a star, for a while, and then, exhausting itself, gutters out, is gone? Was it that I had found, at least in the physical world and in physical science, the sense of stability and order I so desperately needed, so that I could now relax, feel less obsessed, move on? Or was it, perhaps, more simply, that I was growing up, and that ‘growing up’ makes one forget the lyrical, mystical perceptions of childhood, the glory and the freshness of which Wordsworth wrote, so that they fade into the light of common day?
