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Chapter 16
Themes
Key
LitCharts assigns a color and icon to each theme in A Short History of Nearly Everything, which you can use to track the themes throughout the work.
Science, Discovery, and Mystery
Writing, Wonder, and Inspiration
Progress, Sexism, and Dogma
Existence, Awe, and Survival
Summary
Analysis
Without the atmosphere, Earth would be frozen over. Its “gaseous padding” also protects us from deadly objects in space, and without its drag, raindrops would knock us unconscious. Surprisingly, the atmosphere isn’t all that vast. If Earth were the size of a desktop globe, the atmosphere would be as thick as a couple coats of varnish. The atmosphere has four layers: troposphere, stratosphere, mesosphere, ionosphere (or thermosphere). The troposphere is the most vital to us. It rises from ground level up to 7-10 miles high, and it contains all the water and weather we need. Beyond that, Bryson says, is “oblivion.”
Bryson addresses Earth’s atmosphere to emphasize how delicate it is and how essential it is to human survival. Humans can only survive in the first level of the atmosphere (the troposphere), which is essential for our climate. Anything beyond the narrow band of the troposphere is inaccessible to us, meaning that humans can neither descend too far (into the oceans or underground) nor ascend too far (into the atmosphere).
Themes
The stratosphere comes next: its boundary is marked by clouds flattening out. In 1902, Léon-Philippe Teisserenc de Bort discovers the stratosphere while traveling in an air balloon, though humans can’t survive up there because it is oxygen-deprived and -70°F. Beyond the troposphere, the temperature rises again (due to ozone) and then plummets to -130°F, before rising to 2,700°F in the thermosphere. Temperature marks the density of molecules in the atmosphere: it’s warmer at sea level because there are lots of molecules bumping into each other and creating heat. Higher up, the molecules are sparser. When “hopelessly ground-hugging” humans ascend too far, the sparseness of molecules can cause confusion, nausea, hypothermia, and frostbite.
Bort’s experiments show that life beyond the troposphere is impossible for humans, since we can’t survive at the temperatures sustained farther out in the atmosphere. In fact, the higher up humans go, the less oxygen there is, underscoring the extent to which we are limited to Earth’s surface, which Bryson believes we should treat much more carefully than we do. Humans require a very specific density of molecules in the atmosphere to survive, a condition that only exists a few miles into the atmosphere. This shows, once again, how limited our tolerance of the universe at large is.
Themes
Mountaineers call the area above 25,000 feet the “Death Zone,” though altitude sickness sets in above 15,000 feet. Humans can’t tolerate living above 18,000 feet (fetuses, for example, can’t survive pregnancies at those altitudes due to oxygen deprivation). In the 1780s, experimental balloon ascenders assume it’s hotter higher up because they’ll be closer to the sun, but it turns out that the sparsity of molecules actually makes it colder. On a hot day, when one feels the sun on one’s back, this isn’t actually the sun’s heat—rather, the heat is generated by excited molecules that are moving faster and colliding more.
Bryson discusses the “Death Zone” to reemphasize how much of Earth’s surface is off limits to us—specifically, we can’t dwell at high altitudes for extended periods of time. Experimental balloon flights also show that scientific speculation is often fallible, since our prior assumptions about the temperatures in the outer atmosphere are disproved by this ascension.
Themes
Air seems weightless, but actually it’s quite heavy. For instance, changes in air pressure can pile an extra half-ton of air on a sleeping person, but they won’t feel it because their body presses back on the weight and finds equilibrium. Storms expose air’s mass more adequately—when air picks up speed, it can destroy everything in its way. Particles in storm clouds pickup electric charges. Scientists don’t know why, but lighter particles become positively-charged and heavier particles (at the base of clouds) become negatively-charged. Negatively-charged particles are drawn toward the positively-charged Earth, which is what creates lightning. A bolt of lightning travels at 270,000 miles per hour and heats the air around it to 50,000°F, which is hotter than the sun’s surface.
Bryson discusses weather to explain that even the air in the atmosphere that we can tolerate is deceptive—when air moves quickly enough, it’s life-threatening. Similarly, the atmosphere we can tolerate is deadly to us once it picks up an electric charge. Bryson further exposes the limitations of scientific knowledge by stressing that scientists have a limited grasp of why storm clouds pick up electric charges in the first place, showing once again that scientists have much to learn about the world around us.
Themes
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Humans didn’t know much about the atmosphere until aviation took off. Clear-air turbulence, for example, is a random and undetectable pocket of lively air cells in an otherwise calm sky. We have no idea what causes it. More generally, convection causes air currents. Moist, warm air rises until it hits the top of the troposphere and spreads out, cooling as it goes. The cooling makes the air sink, and at ground level it spreads out into the low-pressure spaces that hot air has just left before warming and rising again. At the Equator, weather is the most stable and predictable; elsewhere, it’s far more erratic.
Even when the skies are calm, there are phenomena that scientists can’t explain, such as clear-air turbulence. Part of the reason why humans know so little about the atmosphere is because we’ve only been able to travel at high altitudes in very recent history. All this reinforces the idea that scientific knowledge of the atmosphere is in its infancy, and it has a long way to go.
Themes
The sun’s heat is unevenly distributed, causing differences in air pressure. The atmosphere tries to create equilibrium, which causes wind. Halley first predicts this mechanism in the 1600s, though it takes until 1835 for an engineer named Gustav-Gaspard de Coriolis to work out the details (which is why we now call the mechanism the “Coriolis effect”). Meteorology only takes off as a science in the 19th century, after Dutch instrument maker Daniel Gabriel Fahrenheit invents the first thermometer in 1717 and devises the Fahrenheit scale (which puts freezing at 32° and boiling at 212°). In 1742, a Swedish man named Anders Celsius devises a competing (and more intuitive scale) running from zero to 100.
Bryson again emphasizes how recent our knowledge of the weather is, since adequate tools to measure the weather didn’t exist until the 1700s. Scientific discovery is often limited, as it is here, by technology. Once sufficiently accurate technology develops, however, it’s important for the measurement systems scientists devise (like the way they express their theories) to be clear and accessible. Bryson implies that Celsius’s temperature scale, for example, is more intuitive and therefore better than Fahrenheit’s scale.
Themes
The “father of meteorology,” however, is an English pharmacist named Luke Howard, who names the cloud types in 1803. His system divides clouds into three groups: stratus (layered clouds), cumulous (fluffy clouds), and cirrus (high, thin, feathery clouds). A fourth term, “nimbus” identifies rain clouds. Bryson thinks “the beauty of Howard’s system” is that the terms can be combined to account for every type of cloud, such as “cirrostratus” or “cumulonimbus.” Though Howard’s system has been expanded upon over the years, many of the newer cloud names (like “mammatus” and “mediocris”) haven’t caught on outside esoteric scientific circles. Incidentally, the expression “on cloud nine” comes from cumulonimbus, the ninth and fluffiest cloud in the system.
Bryson further emphasizes the importance of clear and accessible frameworks for making sense of scientific phenomena when he discusses the “beauty” of Howard’s system, which is manageable and flexible, and it accounts for a lot of phenomena without being confusing. Subsequent efforts to render Howard’s system more specific end up being too convoluted to catch on. Bryson stresses this to show that clear expression is an essential part of facilitating scientific progress, which applies as much to systems of classification as it does to other aspects of scientific communication.
Themes
About 60 percent of rainwater returns to the atmosphere within a of couple days through evaporation, though some goes down into ground water and may take thousands of years to return to the sky. Water molecules live in lakes for about a decade before evaporating and for about 100 years in the ocean. Evaporation itself is a fast process. About six million years ago, continental movement closed the Strait of Gibraltar, and the entire Mediterranean dried up in just 1,000 years. The evaporated water fell as freshwater rain in other oceans, reducing their salinity and making them freeze more, triggering an ice age. As Bryson puts it, “a little change in Earth’s dynamics can have repercussions beyond our imagining.”
Bryson shows that even though there are numerous factors contributing to the precarious nature of life of Earth—including asteroids, geological activity, and climate—there are even more factors to consider when scientists think about the ways in which these factors interact. The combination of precipitation and continental movement can dry up oceans and trigger ice ages, showing how vulnerable humans are to the whims of the planet and how lucky we are to have enjoyed a tolerable climate thus far.
Themes
Oceans are also important in meteorology, since rising and falling water molecules (saltier water is denser and falls) create ocean currents, moving water around that subsequently heats and rises as air, with huge effects on Earth’s climate. Changes in salinity, for example, can trigger ice ages. Oceans are also essential for creating stability on Earth. The sun burns 25 percent brighter than it did when the solar system was young, and it should have had “catastrophic” effects on Earth—but tiny marine organisms capture carbon dioxide in rainfall and use it to make their shells, preventing the element from rising back up into the atmosphere and creating a worse greenhouse effect that would warm the planet to disastrous effects.
Bryson emphasizes the extent to which human existence depends on other creatures—for example, tiny marine organisms that that absorb carbon dioxide and prevent Earth from overheating to a temperature that can’t sustain life. Bryson’s motivation is to prompt the reader to question how recklessly humans treat the ecosystems of other creatures. Even if they seem remote or insignificant, even the slightest changes could severely impact our ability to survive.
Themes
Before industrial activity, the atmosphere’s carbon dioxide level is 280 parts per million. By 1958, it rises to 315 parts per million, and today it’s over 360 parts per million. Scientists predict that by the end of the 21st century, it will be 560 parts per million. Earth’s oceans (and forests, which also absorb carbon) are effectively saving us from ourselves, but if we cross over a certain threshold, plants will die and release their carbon, rendering life unsustainable. Luckily, Earth is remarkably good at returning itself to a stable state. The last time this happened, it took only 60,000 years.
Bryson shows that human-caused pollution is on the brink of catastrophe that could render life unsustainable. So far, the effects of industrial activity have been masked by the carbon-absorbing life forms on Earth, but if carbon levels rise too high, humans won’t even be able to rely on them. The planet itself will be fine, but life as we know it will not. Bryson wants the reader to question why humans endanger themselves by wreaking havoc on our already fragile environment.
Themes
