A Short History of Nearly Everything: Special Illustrated Edition

by Bill Bryson

  Mosaic of a Roman wine jug and glass from the second century AD. The wine almost certainly was flavoured with lead—an odd and dangerous practice. (credit 16.7)

  I have brought you a long way to make a small point: a big part of the reason that Earth seems so miraculously accommodating is that we evolved to suit its conditions. What we marvel at is not that it is suitable to life but that it is suitable to our life—and hardly surprising really. It may be that many of the things that make it so splendid to us—well-proportioned Sun, doting Moon, sociable carbon, more molten magma than you can shake a stick at and all the rest—seem splendid simply because they are what we were born to count on. No-one can altogether say.

  Other worlds may harbour beings thankful for their silvery lakes of mercury and drifting clouds of ammonia. They may be delighted that their planet doesn’t shake them silly with its grinding plates or spew messy gobs of lava over the landscape, but rather exists in a permanent non-tectonic tranquillity. Any visitors to the Earth from afar would almost certainly, at the very least, be bemused to find us living in an atmosphere composed of nitrogen, a gas sulkily disinclined to react with anything, and oxygen, which is so partial to combustion that we must place fire stations throughout our cities to protect ourselves from its livelier effects. But even if our visitors were oxygen-breathing bipeds with shopping malls and a fondness for action movies, it is unlikely that they would find the Earth ideal. We couldn’t even give them lunch because all our foods contain traces of manganese, selenium, zinc and other elemental particles at least some of which would be poisonous to them. To them the Earth might not seem a wondrously congenial place at all.

  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.

  So it is possible that the events and conditions that led to the rise of life on the Earth are not quite as extraordinary as we like to think. Still, they were extraordinary enough, and one thing is certain: they will have to do until we find some better.

  1 The discovery of extremophiles in the boiling mudpots of Yellowstone and of similar organisms elsewhere made scientists realize that actually life of a type could range much further than that—even perhaps beneath the icy skin of Pluto. What we are talking about here are the conditions that would produce reasonably complex surface creatures.

  2 Of the remaining four, three are nitrogen and the remaining atom is divided among all the other elements.

  3 Oxygen itself is not combustible; it merely facilitates the combustion of other things. This is just as well, for if oxygen were combustible, each time you lit a match all the air around you would burst into flame. Hydrogen gas, on the other hand, is extremely combustible, as the dirigible Hindenburg demonstrated on 6 May 1937, in Lakehurst, New Jersey, when the hydrogen that gave it lift exploded, killing thirty-six people.

  The ceaseless majesty of “the Great Aerial Ocean,” as Alfred Russel Wallace called Earth’s atmosphere, becomes immediately evident in this photograph from space taken from Skylab. The central swirls are known as von Karman vortices, after the man who first studied them. (credit 17.1)

  INTO THE TROPOSPHERE

  Thank goodness for the atmosphere. It keeps us warm. Without it, Earth would be a lifeless ball of ice with an average temperature of minus 50 degrees Celsius. In addition, the atmosphere absorbs or deflects incoming swarms of cosmic rays, charged particles, ultraviolet rays and the like. Altogether, the gaseous padding of the atmosphere is equivalent to a 4.5-metre thickness of protective concrete, and without it these invisible visitors from space would slice through us like tiny daggers. Even raindrops would pound us senseless if it weren’t for the atmosphere’s slowing drag.

  The most striking thing about our atmosphere is that there isn’t very much of it. It extends upwards for about 190 kilometres, which might seem reasonably bounteous when viewed from ground level, but if you shrank the Earth to the size of a standard desktop globe it would only be about the thickness of a couple of coats of varnish.

  For scientific convenience, the atmosphere is divided into four unequal layers: troposphere, stratosphere, mesosphere and ionosphere (now often called the thermosphere). The troposphere is the part that’s dear to us. It alone contains enough warmth and oxygen to allow us to function, though even it swiftly becomes uncongenial to life as you climb up through it. From ground level to its highest point, the troposphere (or “turning sphere”) is about 16 kilometres thick at the equator and no more than 10 or 11 kilometres high in the temperate latitudes where most of us live. Eighty per cent of the atmosphere’s mass, virtually all the water and thus virtually all the weather are contained within this thin and wispy layer. There really isn’t much between you and oblivion.

  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 sort used in modern skyscrapers would get you there in about twenty minutes, though you would be well advised not to make the trip. Such a rapid ascent without pressurization would, at the very least, result in severe cerebral and pulmonary oedemas, a dangerous excess of fluids in the body’s tissues. When the doors opened at the viewing platform, anyone inside would almost certainly be dead or dying. Even a more measured ascent would be accompanied by a great deal of discomfort. The temperature 10 kilometres up can be minus 57 degrees Celsius and you would need, or at least very much appreciate, supplementary oxygen.

  After you have left the troposphere the temperature soon warms up again, to about 4 degrees Celsius, thanks to the absorptive effects of ozone (something else de Bort discovered on his daring 1902 ascent). It then plunges to as low as minus 90 degrees Celsius in the mesosphere before skyrocketing to 1,500 degrees Celsius or more in the aptly named but very erratic thermosphere, where temperatures can vary by over 500 degrees from day to night—though it must be said that “temperature” at such a height becomes a somewhat notional concept. Temperature is really just a measure of the activity of molecules. At sea level, air molecules are so thick that one molecule can move only the tiniest distance—about eight-millionths of a centimetre, to be precise—before banging into another. Because trillions of molecules are constantly colliding, a lot of heat gets exchanged. But at the height of the thermosphere, at 80 kilometres or more, the air is so thin that any two molecules will be miles apart and hardly ever come into contact. So although each molecule is very warm, there are few interactions between them and thus little heat transference. This is good news for satellites and spaceships, because if the exchange of heat were more efficient any manmade object orbiting at that level would burst into flame.

  Léon-Philippe Teisserenc de Bort, who discovered the invisible but important boundary between troposphere and stratosphere on a balloon flight in 1902. (credit 17.2)

  Even so, spaceships have to take care in the outer atmosphere, particularly on return trips to Earth, as the space shuttle Columbia demonstrated all too tragically in February 2003. Although the atmosphere is very thin, if a craft comes in at too steep an angle—more than about 6 degrees—or too swiftly it can strike enough molecules to generate drag of an exceedingly combustible nature. Conversely, if an incoming vehicle hit the thermosphere at too shallow an angle, it could well bounce
back into space, like a pebble skipped across water.

  But you needn’t venture to the edge of the atmosphere to be reminded of what hopelessly ground-hugging beings we are. As anyone who has spent time in a lofty city will know, you don’t have to rise too many hundreds of metres from sea level before your body begins to protest. Even experienced mountaineers, with the benefits of fitness, training and bottled oxygen, quickly become vulnerable at height to confusion, nausea, exhaustion, frostbite, hypothermia, migraine, loss of appetite and a great many other stumbling dysfunctions. In a hundred emphatic ways the human body reminds its owner that it wasn’t designed to operate so far above sea level.

  “Even under the most favorable circumstances,” the climber Peter Habeler has written of conditions atop Everest, “every step at that altitude demands a colossal effort of will. You must force yourself to make every movement, reach for every handhold. You are perpetually threatened by a leaden, deadly fatigue.” In The Other Side of Everest, the British mountaineer and filmmaker Matt Dickinson records how Howard Somervell, on a 1924 British expedition up Everest, “found himself choking to death after a piece of infected flesh came loose and blocked his windpipe.” With a supreme effort Somervell managed to cough up the obstruction. It turned out to be “the entire mucous lining of his larynx.”

  Bodily distress is notorious above 7,500 metres—the area known to climbers as the Death Zone—but many people become severely debilitated, even dangerously ill, at heights of no more than 4,500 metres or so. Susceptibility has little to do with fitness. Grannies sometimes caper about in lofty situations while their fitter offspring are reduced to helpless, groaning heaps until conveyed to lower altitudes.

  The flight deck of the space shuttle Discovery during a mission in 1992, undergoing the dangerous heating that spacecraft experience during the re-entry phase of a journey—evident here in the pink glow through the windscreens. This danger was dramatically underscored in February 2003 when the space shuttle Columbia broke up on re-entry. (credit 17.3)

  The absolute limit of human tolerance for continuous living appears to be about 5,500 metres, but even people conditioned to living at altitude could not tolerate such heights for long. Frances Ashcroft, in Life at the Extremes, notes that there are Andean sulphur mines at 5,800 metres, but that the miners prefer to descend 460 metres each evening, and climb back up the following day, rather than live continuously at that elevation. People who habitually live at altitude have often spent thousands of years developing disproportionately large chests and lungs, and increasing their density of oxygen-bearing red blood cells by almost a third, though there are limits to how much thickening with red cells the blood supply can stand before it becomes too thick to flow smoothly. Moreover, above 5,500 metres even the most well-adapted women cannot provide a growing foetus with enough oxygen to bring it to its full term.

  In the 1780s, when people began to make experimental balloon ascents in Europe, something that surprised them was how chilly it got as they rose. Logic would seem to indicate that the closer you get to a source of heat, the warmer you should feel. Part of the explanation is that you are not really getting nearer the Sun in any meaningful sense. The Sun is 93 million miles away. To move a few hundred metres closer to it is like taking one step closer to a bushfire in Australia and expecting to smell smoke when you are standing in Ohio. The answer again takes us back to the question of the density of molecules in the atmosphere. Sunlight energizes atoms. It increases the rate at which they jiggle and jounce, and in their enlivened state they crash into one another, releasing heat. When you feel the sun warm on your back on a summer’s day, it’s really excited atoms you feel. The higher you climb, the fewer molecules there are, and so the fewer collisions between them. Air is deceptive stuff. Even at sea level, we tend to think of the air as being ethereal and all but weightless. In fact, it has plenty of bulk, and that bulk often exerts itself. As a marine scientist named Wyville Thomson wrote more than a century ago: “We sometimes find when we get up in the morning, by a rise of an inch in the barometer, that nearly half a ton has been quietly piled upon us during the night, but we experience no inconvenience, rather a feeling of exhilaration and buoyancy, since it requires a little less exertion to move our bodies in the denser medium.” The reason you don’t feel crushed under that extra half-ton of pressure is the same reason your body would not be crushed deep beneath the sea: it is made mostly of incompressible fluids, which push back, equalizing the pressures within and without.

  But get air in motion, as with a hurricane or even a stiff breeze, and you will quickly be reminded that it has very considerable mass. Altogether there are about 5,200 million million tonnes of air around us—25 million tonnes for every square mile of the planet—a not inconsequential volume. When you get millions of tonnes of atmosphere rushing past at 50 or 60 kilometres an hour, it’s hardly a surprise that tree-limbs snap and roof tiles go flying. As Anthony Smith notes, a typical weather front may consist of 750 million tonnes of cold air pinned beneath a billion tonnes of warmer air. Hardly a wonder that the result is at times meteorologically exciting.

  Certainly there is no shortage of energy in the world above our heads. One thunderstorm, it has been calculated, can contain an amount of energy equivalent to four days’ use of electricity for the whole United States. In the right conditions, storm clouds can rise to heights of 10 to 15 kilometres and contain updraughts and downdraughts of over 150 kilometres an hour. These are often side by side, which is why pilots don’t want to fly through them. In all the internal turmoil, particles within the cloud pick up electrical charges. For reasons not entirely understood, the lighter particles tend to become positively charged and to be wafted by air currents to the top of the cloud. The heavier particles linger at the base, accumulating negative charges. These negatively charged particles have a powerful urge to rush to the positively charged Earth and good luck to anything that gets in their way. A bolt of lightning travels at 435,000 kilometres an hour and can heat the air around it to a decidedly crisp 28,000 degrees Celsius, several times hotter than the surface of the sun. At any one moment 1,800 thunderstorms are in progress around the globe—some 40,000 a day. Day and night across the planet, every second about a hundred lightning bolts hit the ground. The sky is a lively place.

  A classic tornado: few forces in nature more potently demonstrate that air, when sufficiently activated, is anything but ethereal. (credit 17.4)

  Much of our knowledge of what goes on up there is surprisingly recent. Jet streams, usually located about 9,000–10,000 metres up, can bowl along at up to nearly 300 kilometres an hour and vastly influence weather systems over whole continents, yet their existence wasn’t suspected until pilots began to fly into them during the Second World War. Even now a great deal of atmospheric phenomena is barely understood. A form of wave motion popularly known as clear-air turbulence occasionally enlivens aeroplane flights. About twenty such incidents a year are serious enough to need reporting. They are not associated with cloud structures or anything else that can be detected visually or by radar. They are just pockets of startling turbulence in the middle of tranquil skies. In a typical incident, a plane en route from Singapore to Sydney was flying over central Australia in calm conditions when it suddenly fell 90 metres—enough to fling unsecured people against the ceiling. Twelve people were injured, one seriously. No-one knows what causes such disruptive cells of air.

  Every second a hundred bolts of lightning streak to Earth across the globe as the electric charges that build up within storm clouds are attracted by the positively charged ground. Earth experiences about 40,000 thunderstorms a day. (credit 17.5)

  The process that moves air around in the atmosphere is the same process that drives the internal engine of the planet, namely convection. Moist, warm air from the equatorial regions rises until it hits the barrier of the tropopause and spreads out. As it travels away from the equator and cools, it sinks. When it hits bottom, some of the sinking air looks for an area of l
ow pressure to fill and heads back for the equator, completing the circuit.

  At the equator the convection process is generally stable and the weather predictably fair, but in temperate zones the patterns are far more seasonal, localized and random, which results in an endless battle between systems of high-pressure and low-pressure air. Low-pressure systems are created by rising air, which conveys water molecules into the sky, forming clouds and eventually rain. Warm air can hold more moisture than cool air, which is why tropical and summer storms tend to be the heaviest. Thus low areas tend to be associated with cloud and rain, and highs generally spell sunshine and fair weather. When two such systems meet, it often becomes manifest in the clouds. For instance, stratus clouds—those unlovable, featureless sprawls that give us our overcast skies—happen when moisture-bearing updraughts lack the oomph to break through a level of more stable air above, and instead spread out, like smoke hitting a ceiling. Indeed, if you watch a smoker sometime, you can get a very good idea of how things work by observing how smoke rises from a cigarette in a still room. At first, it goes straight up (this is called a laminar flow if you need to impress anyone) and then it spreads out in a diffused, wavy layer. The greatest supercomputer in the world, taking measurements in the most carefully controlled environment, cannot accurately predict what forms these ripplings will take, so you can imagine the difficulties that confront meteorologists when they try to forecast such motions in a spinning, windy, large-scale world.

  This photograph taken from the Gemini 12 spacecraft in 1966 shows a jet stream carrying clouds over Egypt and the Red Sea. (credit 17.6)