A Short History of Nearly Everything

by Bill Bryson

Unknown to them, just 50 kilometres away at Princeton University a team of scientists led by Robert Dicke was working on how to find the very thing they were trying so diligently to get rid of. The Princeton researchers were pursuing an idea that had been suggested in the 1940s by the Russian-born astrophysicist George Gamow: that if you looked deep enough into space you should find some cosmic background radiation left over from the Big Bang. Gamow calculated that by the time it had crossed the vastness of the cosmos the radiation would reach Earth in the form of microwaves. In a more recent paper he had even suggested an instrument that might do the job: the Bell antenna at Holmdel. Unfortunately, neither Penzias and Wilson, nor any of the Princeton team, had read Gamow’s paper.

Still unaware of what caused the noise, Wilson and Penzias phoned Dicke at Princeton and described their problem to him in the hope that he might suggest a solution. Dicke realized at once what the two young men had found. “Well, boys, we’ve just been scooped,” he told his colleagues as he hung up the phone.

Incidentally, disturbance from cosmic background radiation is something we have all experienced. Tune your television to any channel it doesn’t receive and about 1 per cent of the dancing static you see is accounted for by this ancient remnant of the Big Bang. The next time you complain that there is nothing on, remember that you can always watch the birth of the universe.

Neither Penzias nor Wilson altogether understood the significance of what they had found until they read about it in the New York Times

For a long time the Big Bang theory had one gaping hole that troubled a lot of people—namely, that it couldn’t begin to explain how we got here. Although 98 per cent of all the matter that exists was created with the Big Bang, that matter consisted exclusively of light gases: the helium, hydrogen and lithium that we mentioned earlier. Not one particle of the heavy stuff so vital to our own being—carbon, nitrogen, oxygen and all the rest—emerged from the gaseous brew of creation. But—and here’s the troubling point—to forge these heavy elements, you need the kind of heat and energy thrown off by a Big Bang. Yet there has been only one Big Bang and it didn’t produce them.

So if Pluto really is a planet, it is certainly an odd one. It is very tiny: just one quarter of 1 per cent as massive as Earth. If you set it down on top of the United States, it would cover not quite half the lower forty-eight states.

Neptune in reality isn’t just a little bit beyond Jupiter, it’s way beyond Jupiter—five times further from Jupiter than Jupiter is from us, so far out that it receives only 3 per cent as much sunlight as Jupiter.

On a diagram of the solar system to scale, with the Earth reduced to about the diameter of a pea, Jupiter would be over 300 metres away and Pluto would be two and a half kilometres distant (and about the size of a bacterium, so you wouldn’t be able to see it anyway). On the same scale, Proxima Centauri, our nearest star, would be 16,000 kilometres away.

Maskelyne realized that the nub of the problem lay with finding a mountain of sufficiently regular shape to judge its mass. At his urging, the Royal Society agreed to engage a reliable figure to tour the British Isles to see if such a mountain could be found. Maskelyne knew just such a person—the astronomer and surveyor Charles Mason. Maskelyne and Mason had become friends eleven years earlier while engaged in a project to measure an astronomical event of great importance: the passage of the planet Venus across the face of the Sun. The tireless Edmond Halley had suggested years before that if you measured one of these passages from selected points on the Earth, you could use the principles of triangulation to work out the distance from the Earth to the Sun, and thence to calibrate the distances to all the other bodies in the solar system. Unfortunately, transits of Venus, as they are known, are an irregular occurrence. They come in pairs eight years apart, but then are absent for a century or more, and there were none in Halley’s lifetime.3 But the idea simmered and when the next transit fell due in 1761, nearly two decades after Halley’s death, the scientific world was ready—indeed, more ready than it had been for an astronomical event before.

Unluckier still was Guillaume le Gentil, whose experiences are wonderfully summarized by Timothy Ferris in Coming of Age in the Milky Way. Le Gentil set off from France a year ahead of time to observe the transit from India, but various setbacks left him still at sea on the day of the transit—just about the worst place to be, since steady measurements were impossible on a pitching ship. Undaunted, Le Gentil continued on to India to await the next transit in 1769. With eight years to prepare, he erected a first-rate viewing station, tested and retested his instruments and had everything in a state of perfect readiness. On the morning of the second transit, 4 June 1769, he awoke to a fine day; but, just as Venus began its pass, a cloud slid in front of the Sun and remained there for almost exactly the duration of the transit of three hours, fourteen minutes and seven seconds. Stoically, Le Gentil packed up his instruments and set off for the nearest port, but en route he contracted dysentery and was laid up for nearly a year. Still weakened, he finally made it onto a ship. It was nearly wrecked in a hurricane off the African coast. When at last he reached home, eleven and a half years after setting off, and having achieved nothing, he discovered that his relatives had had him declared dead in his absence and had enthusiastically plundered his estate.

Cavendish is a book in himself. Born into a life of sumptuous privilege—his grandfathers were dukes, respectively, of Devonshire and Kent—he was the most gifted English scientist of his age, but also the strangest. He suffered, in the words of one of his few biographers, from shyness to a “degree bordering on disease.” Any human contact was for him a source of the deepest discomfort.

When assembled, Michell’s apparatus looked like nothing so much as an eighteenth-century version of a Nautilus weight-training machine. It incorporated weights, counterweights, pendulums, shafts and torsion wires. At the heart of the machine were two 350-pound lead balls, which were suspended beside two smaller spheres. The idea was to measure the gravitational deflection of the smaller spheres by the larger ones, which would allow the first measurement of the elusive force known as the gravitational constant, and from which the weight (strictly speaking the mass)5 of the Earth could be deduced.

Because gravity holds planets in orbit and makes falling objects land with a bang, we tend to think of it as a powerful force, but it isn’t really. It is only powerful in a kind of collective sense, when one massive object, like the Sun, holds onto another massive object, like the Earth. At an elemental level gravity is extraordinarily unrobust. Each time you pick up a book from a table or a coin from the floor you effortlessly overcome the gravitational exertion of an entire planet. What Cavendish was trying to do was measure gravity at this extremely featherweight level.

Among the questions that attracted interest in that fanatically inquisitive age was one that had puzzled people for a very long time—namely, why ancient clam shells and other marine fossils were so often found on mountaintops. How on earth did they get there? Those who thought they had a solution fell into two opposing camps. One group, known as the Neptunists, were convinced that everything on the Earth, including sea shells in improbably lofty places, could be explained by rising and falling sea levels. They believed that mountains, hills and other features were as old as the Earth itself, and were changed only when water sloshed over them during periods of global flooding.

Opposing them were the Plutonists, who noted that volcanoes and earthquakes, among other enlivening agents, continually changed the face of the planet but clearly owed nothing to wayward seas. The Plutonists also raised awkward questions about where all the water went when it wasn’t in flood. If there was enough of it at times to cover the Alps, then where, pray, was it during times of tranquillity, such as now? Their belief was that the Earth was subject to profound internal forces as well as surface ones. However, they couldn’t convincingly explain how all those clam shells got up there.

In 1785 Hutton worked his ideas up into a long paper, which was read at consecutive meetings of the Royal Society of Edinburgh. It attracted almost no notice at all. It’s not hard to see why. Here, in part, is how he presented it to his audience: In the one case, the forming cause is in the body which is separated; for, after the body has been actuated by heat, it is by the reaction of the proper matter of the body, that the chasm which constitutes the vein is formed. In the other case, again, the cause is extrinsic in relation to the body in which the chasm is formed. There has been the most violent fracture and divulsion; but the cause is still to seek; and it appears not in the vein; for it is not every fracture and dislocation of the solid body of our earth, in which minerals, or the proper substances of mineral veins, are found. Needless to say, almost no-one in the audience had the faintest idea what he was talking about. Encouraged by his friends to expand his theory, in the touching hope that he might somehow stumble onto clarity in a more expansive format, Hutton spent the next ten years preparing his magnum opus, which was published in two volumes in 1795.

Not quite as remarkable in character but more influential than all the others combined was Charles Lyell. Lyell was born in the year that Hutton died and only 70 miles away, in the village of Kinnordy. Though Scottish by birth, he grew up in the far south of England, in the New Forest of Hampshire, because his mother was convinced that Scots were feckless drunks. As was generally the pattern with nineteenth-century gentlemen scientists, Lyell came from a background of comfortable wealth and intellectual vigour. His father, also named Charles, had the unusual distinction of being a leading authority on the poet Dante and on mosses. (Orthotricium lyelli, which most visitors to the English countryside will at some time have sat on, is named for him.) From his father Lyell gained an interest in natural history, but it was at Oxford, where he fell under the spell of the Reverend William Buckland—he of the flowing gowns—that the young Lyell began his lifelong devotion to geology.

Between Hutton’s day and Lyell’s there arose a new geological controversy, which largely superseded, but is often confused with, the old Neptunian-Plutonian dispute. The new battle became an argument between catastrophism and uniformitarianism—unattractive terms for an important and very long-running dispute. Catastrophists, as you might expect from the name, believed that the Earth was shaped by abrupt cataclysmic events—floods, principally, which is why catastrophism and Neptunism are often wrongly bundled together. Catastrophism was particularly comforting to clerics like Buckland because it allowed them to incorporate the biblical flood of Noah into serious scientific discussions. Uniformitarians, by contrast, believed that changes on Earth were gradual and that nearly all earth processes happened slowly, over immense spans of time. Hutton was much more the father of the notion than Lyell, but it was Lyell most people read, and so he became in most people’s minds, then and now, the father of modern geological thought.

Lyell believed that the Earth’s shifts were uniform and steady—that everything that had ever happened in the past could be explained by events still going on today. Lyell and his adherents didn’t just disdain catastrophism, they detested it. Catastrophists believed that extinctions were part of a series in which animals were repeatedly wiped out and replaced with new sets—a belief that the naturalist T. H. Huxley mockingly likened to “a succession of rubbers of whist, at the end of which the players upset the table and called for a new pack.” It was too convenient a way to explain the unknown. “Never was there a dogma more calculated to foster indolence, and to blunt the keen edge of curiosity,” sniffed Lyell.

Because the British were the most active in the early years of the discipline, British names are predominant in the geological lexicon. Devonian is of course from the English county of Devon. Cambrian comes from the Roman name for Wales, while Ordovician and Silurian recall ancient Welsh tribes, the Ordovices and Silures. But with the rise of geological prospecting elsewhere, names began to creep in from all over. Jurassic refers to the Jura Mountains on the border of France and Switzerland. Permian recalls the former Russian province of Perm in the Ural Mountains. For Cretaceous (from the Latin for chalk) we are indebted to a Belgian geologist with the perky name of J. J. d’Omalius d’Halloy.

Originally, geological history was divided into four spans of time: primary, secondary, tertiary and quaternary. The system was too neat to last, and soon geologists were contributing additional divisions while eliminating others. Primary and secondary fell out of use altogether, while quaternary was discarded by some but kept by others. Today only tertiary remains as a common designation everywhere, even though it no longer represents a third period of anything.

Then come Lyell’s epochs—the Pleistocene, Miocene, and so on—which apply only to the most recent (but palaeontologically busy) 65 million years; and finally we have a mass of finer subdivisions known as stages or ages. Most of these are named, nearly always awkwardly, after places: Illinoian, Desmoinesian, Croixian, Kimmeridgian and so on in like vein. Altogether, according to John McPhee, these number in the “tens of dozens.” Fortunately, unless you take up geology as a career, you are unlikely ever to hear any of them again.

By the middle of the nineteenth century most learned people thought the Earth was at least a few million years old, perhaps even some tens of millions years old, but probably not more than that. So it came as a surprise when in 1859, in On the Origin of Species, Charles Darwin announced that the geological processes that created the Weald, an area of southern England stretching across Kent, Surrey and Sussex, had taken, by his calculations, 306, 662, 400 years to complete. The assertion was remarkable partly for being so arrestingly specific but even more for flying in the face of accepted wisdom about the age of the Earth.3 It proved so contentious that Darwin withdrew it from the third edition of the book. The problem at its heart remained, however. Darwin and his geological friends needed the Earth to be old, but no-one could come up with a way to make it so.

The sentiment is understandable, for Kelvin really was a kind of Victorian superman. He was born in 1824 in Belfast, the son of a professor of mathematics at the Royal Academical Institution who soon afterwards transferred to Glasgow. There Kelvin proved himself such a prodigy that he was admitted to Glasgow University at the exceedingly tender age of ten. By the time he had reached his early twenties, he had studied at institutions in London and Paris, graduated from Cambridge (where he won the university’s top prizes for rowing and mathematics, and somehow found time to launch a musical society as well), been elected a fellow of Peterhouse, and written (in French and English) a dozen papers in pure and applied mathematics of such dazzling originality that he had to publish them anonymously for fear of embarrassing his superiors. At the age of twenty-two he returned to Glasgow to take up a professorship in natural philosophy, a position he would hold for the next fifty-three years.

In 1787, someone in New Jersey—exactly who now seems to be forgotten—found an enormous thigh bone sticking out of a stream bank at a place called Woodbury Creek. The bone clearly didn’t belong to any species of creature still alive, certainly not in New Jersey. From what little is known now, it is thought to have belonged to a hadrosaur, a large duckbilled dinosaur. At the time, dinosaurs were unknown. The bone was sent to Dr Caspar Wistar, the nation’s leading anatomist, who described it at a meeting of the American Philosophical Society in Philadelphia that autumn. Unfortunately, Wistar failed completely to recognize the bone’s significance and merely made a few cautious and uninspired remarks to the effect that it was indeed a whopper. He thus missed the chance, half a century ahead of anyone else, to be the discoverer of dinosaurs. Indeed, the bone excited so little interest that it was put in a storeroom and eventually disappeared altogether. So the first dinosaur bone ever found was also the first to be lost.

To interpret rocks, there needs to be some means of correlation, a basis on which you can tell that those carboniferous rocks from Devon are younger than these Cambrian rocks from Wales. Smith’s insight was to realize that the answer lay with fossils. At every change in rock strata certain species of fossils disappeared while others carried on into subsequent levels. By noting which species appeared in which strata, you could work out the relative ages of rocks wherever they appeared. Drawing on his knowledge as a surveyor, Smith began at once to make a map of Britain’s rock strata, which would be published after many trials in 1815 and would become a cornerstone of modern geology. (The story is comprehensively covered in Simon Winchester’s popular book The Map that Changed the World.)

It wasn’t simply that Anning was good at spotting fossils—though she was unrivalled at that—but that she could extract them with the greatest delicacy and without damage. If you ever have the chance to visit the hall of ancient marine reptiles at the Natural History Museum in London, I urge you to take it, for there is no other way to appreciate the scale and beauty of what this young woman achieved working virtually unaided with the most basic tools in nearly impossible conditions. The plesiosaur alone took her ten years of patient excavation. Although untrained, Anning was also able to provide competent drawings and descriptions for scholars. But even with the advantage of her skills, significant finds were rare and she passed most of her life in considerable poverty. It would be hard to think of a more overlooked person in the history of palaeontology than Mary Anning, but in fact there was one who came painfully close. His name was Gideon Algernon Mantell and he was a country doctor in Sussex.

Mantell prepared a paper for delivery to the Royal Society. Unfortunately, it emerged that another dinosaur had been found at a quarry in Oxfordshire and had just been formally described—by the Reverend Buckland, the very man who had urged him not to work in haste. It was the megalosaurus, and the name was actually suggested to Buckland by his friend Dr. James Parkinson, the would-be radical and eponym for Parkinson’s disease. Buckland, it may be recalled, was foremost a geologist, and he showed it with his work on megalosaurus. In his report, for the Transactions of the Geological Society of London, he noted that the creature’s teeth were not attached directly to the jawbone, as in lizards, but placed in sockets, in the manner of crocodiles. But, having noticed this much, Buckland failed to realize what it meant: namely, that megalosaurus was an entirely new type of creature. Still, although his report demonstrated little acuity or insight, it was the first published description of a dinosaur—and so it is to Buckland, rather than the far more deserving Mantell, that the credit goes for the discovery of this ancient line of beings.

But it was for his work with dinosaurs that Owen is remembered. He coined the term dinosauria in 1841. It means “terrible lizard” and was a curiously inapt name. Dinosaurs, as we now know, weren’t all terrible—some were no bigger than rabbits and probably extremely retiring—and the one thing they most emphatically were not was lizards, which are actually of a much older (by 30 million years) lineage. Owen was well aware that the creatures were reptilian and had at his disposal a perfectly good Greek word, herpeton, but for some reason chose not to use it. Another, more excusable error (given the paucity of specimens at the time) was his failure to note that dinosaurs constitute not one but two orders of reptiles: the bird-hipped ornithischians and the lizard-hipped saurischians.

And his fancy equipment did in fact come in very handy. For years, he and Mme Lavoisier occupied themselves with extremely exacting studies requiring the finest measurements. They determined, for instance, that a rusting object doesn’t lose weight, as everyone had long assumed, but gains weight—an extraordinary discovery. Somehow, as it rusted the object was attracting elemental particles from the air. It was the first realization that matter can be transformed but not eliminated. If you burned this book now, its matter would be changed to ash and smoke, but the net amount of stuff in the universe would be the same. This became known as the conservation of mass, and it was a revolutionary concept. Unfortunately, it coincided with another type of revolution—the French one—and in this one Lavoisier was entirely on the wrong side. Not only was he a member of the hated Ferme Générale, but he had enthusiastically built the wall that enclosed Paris—an edifice so loathed that it was the first thing attacked by the rebellious citizens. Capitalizing on this, in 1791 Marat, now a leading voice in the National Assembly, denounced Lavoisier and suggested that it was well past time for his hanging.

A hundred years after his death, a statue of Lavoisier was erected in Paris and much admired until someone pointed out that it looked nothing like him. Under questioning, the sculptor admitted that he had used the head of the mathematician and philosopher the Marquis de Condorcet—apparently he had a spare—in the hope that no-one would notice or, having noticed, would care. In the second regard he was correct.

Soon after taking up his position, Davy began to bang out new elements one after another—potassium, sodium, magnesium, calcium, strontium, and aluminum or aluminium (depending on which branch of English you favour).1 He discovered so many elements not so much because he was serially astute as because he developed an ingenious technique of applying electricity to a molten substance—electrolysis, as it is known. Altogether he discovered a dozen elements, a fifth of the known total of his day. Davy might have done far more, but unfortunately as a young man he developed an abiding attachment to the buoyant pleasures of nitrous oxide.

Chemists also used a bewildering variety of symbols and abbreviations, often self-invented. Sweden’s J. J. Berzelius brought a much-needed measure of order to matters by decreeing that the elements be abbreviated on the basis of their Greek or Latin names, which is why the abbreviation for iron is Fe (from the Latin ferrum) and for silver is Ag (from the Latin argentum). That so many of the other abbreviations accord with their English names (N for nitrogen, O for oxygen, H for hydrogen and so on) reflects English’s latinate nature, not its exalted status. To indicate the number of atoms in a molecule, Berzelius employed a superscript notation, as in H2O. Later, for no special reason, the fashion became to render the number as subscript: H2O.

As is often the way in science, the principle had actually been anticipated three years previously by an amateur chemist in England named John Newlands. He suggested that when elements were arranged by weight they appeared to repeat certain properties—in a sense to harmonize—at every eighth place along the scale. Slightly unwisely, for this was an idea whose time had not quite yet come, Newlands called it the Law of Octaves and likened the arrangement to the octaves on a piano keyboard. Perhaps there was something in Newlands’ manner of presentation, but the idea was considered fundamentally preposterous and widely mocked. At gatherings, droller members of the audience would sometimes ask him if he could get his elements to play them a little tune. Discouraged, Newlands gave up pushing the idea and soon dropped out of sight altogether. Mendeleyev used a slightly different approach, placing his elements into groups of seven, but employed fundamentally the same premise. Suddenly the idea seemed brilliant and wondrously perceptive. Because the properties repeated themselves periodically, the invention became known as the Periodic Table.

Mendeleyev was said to have been inspired by the card game known as solitaire in North America and patience elsewhere, wherein cards are arranged by suit horizontally and by number vertically. Using a broadly similar concept, he arranged the elements in horizontal rows called periods and vertical columns called groups. This instantly showed one set of relationships when read up and down and another when read from side to side. Specifically, the vertical columns put together chemicals that have similar properties. Thus copper sits on top of silver and silver sits on top of gold because of their chemical affinities as metals, while helium, neon and argon are in a column made up of gases. (The actual, formal determinant in the ordering is something called their electron valences, and if you want to understand them you will have to enrol in evening classes.) The horizontal rows, meanwhile, arrange the chemicals in ascending order by the number of protons in their nuclei—what is known as their atomic number.

Today we have “120 or so” known elements—92 naturally occurring ones plus a couple of dozen that have been created in labs. The actual number is slightly contentious because the heavy, synthesized elements exist for only millionths of seconds and chemists sometimes argue over whether they have really been detected or not. In Mendeleyev’s day just sixty-three elements were known, but part of his cleverness was to realize that the elements as then known didn’t make a complete picture, that many pieces were missing. His table predicted, with pleasing accuracy, where new elements would slot in when they were found.

If you needed to illustrate the idea of nineteenth-century America as a land of opportunity, you could hardly improve on the life of Albert Michelson. Born in 1852 on the German-Polish border to a family of poor Jewish merchants, he came to the United States with his family as an infant and grew up in a mining camp in California’s gold rush country where his father ran a dry goods business. Too poor to pay for college, he travelled to Washington, DC, and took to loitering by the front door of the White House so that he could fall in beside Ulysses S. Grant when the President emerged for his daily constitutional. (It was clearly a more innocent age.) In the course of these walks, Michelson so ingratiated himself with the President that Grant agreed to secure for him a free place at the US Naval Academy. It was there that Michelson learned his physics.

Ten years later, by now a professor at the Case School in Cleveland, Michelson became interested in trying to measure something called the ether drift—a kind of headwind produced by moving objects as they ploughed through space. One of the predictions of Newtonian physics was that the speed of light as it pushed through the ether should vary with respect to an observer depending on whether the observer was moving towards the source of light or away from it, but no-one had figured out a way to measure this. It occurred to Michelson that if you took careful measurements, with a very precise instrument, at opposite seasons, and compared light’s travel time between the two, you would have your answer.

Midgley was an engineer by training and the world would no doubt have been a safer place if he had stayed so. Instead, he developed an interest in the industrial applications of chemistry. In 1921, while working for the General Motors Research Corporation in Dayton, Ohio, he investigated a compound called tetraethyl lead (also known, confusingly, as lead tetraethyl), and discovered that it significantly reduced the juddering condition known as engine knock.

Lead is a neurotoxin. Get too much of it and you can irreparably damage the brain and central nervous system. Among the many symptoms associated with over-exposure are blindness, insomnia, kidney failure, hearing loss, cancer, palsies and convulsions. In its most acute form it produces abrupt and terrifying hallucinations, disturbing to victims and onlookers alike, which generally then give way to coma and death. You really don’t want to get too much lead into your system.

Buoyed by the success of leaded petrol, Midgley now turned to another technological problem of the age. Refrigerators in the 1920s were often appallingly risky because they used insidious and dangerous gases that sometimes seeped out. One leak from a refrigerator at a hospital in Cleveland, Ohio, in 1929 killed more than a hundred people. Midgley set out to create a gas that was stable, non-flammable, non-corrosive and safe to breathe. With an instinct for the regrettable that was almost uncanny, he invented chlorofluorocarbons, or CFCs. Seldom has an industrial product been more swiftly or unfortunately embraced. CFCs went into production in the early 1930s and found a thousand applications in everything from car air-conditioners to deodorant sprays before it was noticed, half a century later, that they were devouring the ozone in the stratosphere. As you will be aware, this was not a good thing.

Thomas Midgley, the American inventor who had the distinction of devising two of the twentieth century’s most regrettable compounds—chlorofluorocarbons and leaded petrol.

If you were interested in finding out the ages of things, the University of Chicago in the 1940s was the place to be. Willard Libby was in the process of inventing radiocarbon dating, allowing scientists to get an accurate reading of the age of bones and other organic remains, something they had never been able to do before.

Libby’s idea was so useful that he would be awarded a Nobel Prize for it in 1960. It was based on the realization that all living things have within them an isotope of carbon called carbon-14, which begins to decay at a measurable rate the instant they die. Carbon-14 has a half-life—that is, the time it takes for half of any sample to disappear—of about 5,600 years, so by working out how much of a given sample of carbon had decayed, Libby could get a good fix on the age of an object—though only up to a point. After eight half-lives, only 0.39 per cent of the original radioactive carbon remains, which is too little to make a reliable measurement, so radiocarbon dating works only for objects up to forty thousand or so years old.

Harrison Brown, who created a refined technique for determining the age of very ancient rocks, enabling Clair Patterson finally to make an accurate assessment of Earth’s age: 4.55 billion years.

Patterson quickly established that we had a lot of lead in the atmosphere—still do, in fact, since lead never goes away—and that about 90 per cent of it appeared to come from car exhaust pipes; but he couldn’t prove it. What he needed was a way to compare lead levels in the atmosphere now with the levels that existed before 1923, when tetraethyl lead began to be commercially produced. It occurred to him that ice cores could provide the answer. It was known that snowfall in places like Greenland accumulates into discrete annual layers (because seasonal temperature differences produce slight changes in coloration from winter to summer). By counting back through these layers and measuring the amount of lead in each, he could work out global atmospheric lead concentrations at any time for hundreds, or even thousands, of years. The notion became the foundation of ice core studies, on which much modern climatological work is based. What Patterson found was that before 1923 there was almost no lead in the atmosphere, and that since that time lead levels had climbed steadily and dangerously. He now made it his life’s quest to get lead taken out of petrol. To that end, he became a constant and often vocal critic of the lead industry and its interests.

To his great credit, Patterson never wavered. Eventually his efforts led to the introduction of the Clean Air Act of 1970 and finally to the removal from sale of all leaded petrol in the United States in 1986. Almost immediately lead levels in the blood of Americans fell by 80 per cent. But because lead is for ever, Americans alive today each have about 625 times more lead in their blood than people did a century ago. The amount of lead in the atmosphere also continues to grow, quite legally, by about a hundred thousand tonnes a year, mostly from mining, smelting and industrial activities. The United States also banned lead in indoor paint, “44 years after most of Europe,” as McGrayne notes. Remarkably, considering its startling toxicity, lead solder was not removed from American food containers until 1993.

Other organisms do, of course, manage to deal with the pressures at depth, though quite how some of them do so is a mystery. The deepest point in the ocean is the Mariana Trench in the Pacific. There, some 11.3 kilometres down, the pressures rise to over 16,000 pounds per square inch. We have managed just once, briefly, to send humans to that depth in a sturdy diving vessel, yet it is home to colonies of amphipods, a type of crustacean similar to shrimp but transparent, which survive without any protection at all. Most oceans are of course much shallower, but even at the average ocean depth of 4 kilometres the pressure is equivalent to being squashed beneath a stack of fourteen loaded cement trucks.

The physicist Richard Feynman used to make a joke about a posteriori conclusions—reasoning from known facts back to possible causes. “You know, the most amazing thing happened to me tonight,” he would say. “I saw a car with the licence plate ARW 357. Can you imagine? Of all the millions of licence plates in the state, what was the chance that I would see that particular one tonight? Amazing!” His point, of course, is that it is easy to make any banal situation seem extraordinary if you treat it as fateful.

Beyond the troposphere is the stratosphere. When you see the top of a storm cloud flattening out into the classic anvil shape, you are looking at the boundary between the troposphere and the stratosphere. This invisible ceiling is known as the tropopause and was discovered in 1902 by a Frenchman in a balloon, Léon-Philippe Teisserenc de Bort. Pause in this sense doesn’t mean to stop momentarily but to cease altogether; it’s from the same Greek root as menopause. Even at the troposphere’s greatest extent, the tropopause is not very distant. A fast lift of the