Zoom: From Atoms and Galaxies to Blizzards and Bees: How Everything Moves (19 page)

Which brings up the issue of our entire bodies in motion. Walking. All around us, people swing their limbs. The average person’s leg and arm completes its back-and-forth cycle in about a second and a half. Meaning we take two full steps in three seconds.

We can deliberately choose to walk faster or slower, of course. Yet people and animals have a natural gait they’ll unconsciously use whenever possible. A leg “wants” to oscillate just the way a playground swing does. It has a natural cycle whose period depends solely on its length. We all know that a playground swing on a nice long chain has a satisfying, long-period oscillation, while a short chain yields a quick, jumpy back-and-forth ride. This is the pendulum effect.

It was discovered by none other than Galileo. The place where Galileo first noticed this fantastic property of naturally swinging objects is still there, unchanged to this day. If you ever go to the Leaning Tower of Pisa, you can’t miss the duomo, the cathedral, adjacent to it. Within that huge, dark, musty space, chandeliers still hang on chains from the ceiling far above. Sometimes, especially on a windy day, these chandeliers display a slight, achingly slow, back-and-forth motion. In 1582, during mass, Galileo—perhaps so enraptured by the liturgy that he stared blankly up toward the ceiling—made the startling discovery that the length of time it took for these chandeliers to complete each swing never varied. It was about nine seconds, whether they were moving a few inches or several feet. This observation apparently stewed in his brain awhile.

The Piazza del Duomo, in Pisa, Italy, is the site of two great motion-related events. According to his pupil Vincenzo Viviani, Galileo dropped a light object and a heavy object from the leaning tower in 1589, proving that they fall at the same speed. Seven years earlier, in 1582, in the great duomo in the foreground, Galileo first noticed the pendulum effect.

A long while. Fully twenty years later, he decided to make a study of this pendulum effect. Beginning in 1602, he wrote to tell someone that the heaviness of the bob, or weight, at the end of a chain, wire, or string doesn’t influence the period of the swing. Nor, essentially, does the amplitude. Meaning that if you give a child a tiny, barely noticeable push on a swing so that it only moves a few inches, the time it takes to go back and forth won’t be different from what it’ll be if you deliver a huge push that takes her high up, nearly sideways, and then wildly back up the other side.

Galileo realized that this property, called isochronism, would make pendulums useful as clocks. It means that the period of swing depends solely on the length of the string. There’s a natural swing rate to everything. Any weight on a thirty-nine-inch string—very close to but not exactly one meter—creates a perfect one-second swing, meaning two seconds for the complete back-and-forth period. (This length might logically seem the basis for the meter, but no: the meter was originally fashioned to equal one ten-millionth the distance between the equator and either pole.) Eventually, grandfather clocks were duly built with pendulums of the correct length to tick-tick faultless seconds.

By chance, most men have legs of about that same length or a few inches more. As they swivel from their hip sockets, these hairy weights “want” to complete a back-and-forth swing in about 1.5 seconds.1 For a five-feet-four-inch woman, the gait is a bit faster.

Again, the body naturally uses the easiest, least energy-consuming gaits. If you’re in a hurry you can obviously expend extra energy and go as fast as you like. These days we physically hurl ourselves at speeds that would have bewildered all but the last eight of the 12,500 generations of Homo sapiens that went (more slowly) before us.

Do human travel velocities count as “natural” motion? We normally separate our technological triumphs from things like blowing sand and charging elephants. But maybe that’s too arbitrary. Our brains and our restlessness developed beyond our control; perhaps our own meanderings are as natural as that of the Mississippi.

So let’s briefly outline how fast entire bodies move. This would have been an easy task during the first two thousand centuries of human history. We walked or ran. An hour of effort let us sweatily advance ourselves between three and ten miles. After we tamed horses, we galloped for short distances.

Average Americans walk 65,000 miles in their lives. More than twice around the world. That’s not so different from our ancestors. But this is: we each travel a million miles over the course of a lifetime. Such a degree of movement was unheard of until recently. (And not just because the word million didn’t exist until the fourteenth century, before which the largest number was a myriad—ten thousand.) Danger per mile was so much higher, even as recently as the Civil War era, that few would have lived to accumulate that many frequent-traveler points. True, an extraordinary nineteenth-century railway conductor or seaman might have accrued enough to join the million-mile club—but he’d likely have lots of scars to prove it.

The pivotal point in human travel arrived two centuries ago. Huge changes unfolded between 1790 and 1830. At the start of that period, most people traveled by carriage, riding along potholed dirt roads at between four and six miles per hour. By all accounts it was torture. If your route took you over the best roads, between major cities such as New York and Boston, you could make the trip in five or six days. You’d be hot or cold, beset by buzzing insects attracted by the horses themselves, and it was not fun.

Two major improvements boosted long-distance transportation to a new and celebrated average speed of between eight and nine miles per hour. The first was the introduction of raised macadamized roads with side trenches for drainage. This meant laying three courses of stones, the largest on the bottom and the finest compacted at the top. Riding on these “high” ways dramatically reduced lurching and bumping.2

The second speed booster was the stagecoach. By the 1830s, carriage companies used relays of horses that would be changed every forty miles or so along the route. With fresh horses attached at regular intervals, or stages, the New-York-to-Boston run was cut to one and a half days.

At around this time, steamboats increasingly plied waterways, starting with the North River Steamboat, soon popularly called the Clermont, which journeyed up the Hudson beginning in 1807, aided by the Erie Canal, which opened in 1825. Railroads (always called railways then) grew dramatically, too, and in the late 1830s they were routinely clocking in at between fifteen and twenty miles per hour. This was unprecedented, nonstop speed, and people paused from working in their fields to watch the wood-fired, smoke-belching, canopied carriages pass by, their occupants inhaling facefuls of soot and embers. By 1840, three thousand miles of track had been laid, mostly in the northeast, and that Boston trip now took a single day.

Children in the 1790s grew up to be astonished at the rapid change in travel speed they’d witnessed by the time they were grandparents in their fifties. It was a whole new world. There was a downside, however. As people increasingly voyaged by train and boat, roads were neglected and took on a rutted dilapidation by the mid-nineteenth century. They became suitable for local transportation only—the way you’d get into town from your farm or visit relatives a few towns over. This turnaround didn’t reverse until the infatuation with the automobile took hold two generations later.

Cars were originally hailed as environmental saviors because they held the promise of eradicating the stench of horses, the thick swarms of flies and disease their feces attracted, and the unrelenting din of horseshoes on urban cobblestones. In today’s Los Angeles and Beijing, few probably regard cars as “green”—but they do carry our story to the present, when we routinely hurl ourselves at seventy miles per hour along the freeway. Our very fastest body speeds? On the ground it’s 180 miles per hour. That’s the rate of European, Japanese, and Chinese bullet trains. It’s also the takeoff speed of heavy jumbo jets just before they’re airborne. It’s the fastest most of us have ever moved on the ground.

In the air (a method of travel that marked a third major milestone), the speed depends on the jet. The normal, most efficient cruising speed of the good old Boeing 747 is 655 miles per hour. The newer giant double-deck Airbus A380 is a tad slower at 647 miles per hour, as is the Boeing 787.3

When we’re not relying on technology to propel our bodies, our fastest movements are involuntary. One of these is legendary. Yet the sneeze usually begins in slow motion. The first phase of the sneezing reflex is a nasal tingling that follows stimulation by a chemical or physical irritant. Or sometimes by a strange bright-light response called the photic sneeze reflex, as when people emerge from a movie matinee into brilliant sunshine. Whatever the basis, the initial odd tingling grows until it reaches a level that triggers the far more animated second phase.

It’s this so-called efferent phase that consists of eye closing, a sudden, uncontrollable deep inhalation, and then blowing out air while closing the throat and increasing air pressure in the chest. The reflexive sudden opening of the throat releases a supernova-type air rush through the mouth and nose, explosively expelling any irritants.

A sneeze can release forty thousand particles at high speed. What speed is it, exactly? You’ll find all sorts of disparate velocity figures on the Web. Some claim that this is the only human-body movement that breaks the sound barrier. The truth, while still impressive, doesn’t come close to such a 768-mile-an-hour achievement. The TV show MythBusters actually measured sneezes; their subjects’ fastest was thirty-nine miles per hour. In a medical setting and using trustworthy equipment, the fastest recorded sneeze was clocked at 102 miles per hour. For some reason, the Guinness World Records lists the greatest sneeze a bit slower than this, at 71.5 miles per hour, or 115 kilometers per hour. Definitely fast enough to count as the highest-velocity body motion.4

A longstanding puzzle is why sneezers involuntarily close their eyes during the event. The best guess is that we are protecting our eyes from the ultrafast spray of germs and particulate matter. Another possible reason is that a sneeze is a unique reflex that involves nearly the entire body. Many muscles contract—including those in the nose, throat, abdomen, diaphragm, and back. Even the sphincters contract. This is why people with weak bladders may release a bit of urine during a sneeze. So the closing of the eyes is just part of a much larger, unique display of physiological violence.

It all originates in a primitive part of the brain called the medulla oblongata, in the brain stem, which is present in countless other animals who sneeze pretty much the same way we do.

So we just can’t escape this hurry-up universe. We can’t even avoid it by staying in bed.

We take it with us, inside our skulls and under our skin.

Earth’s Greatest Assets Are Liquid

But ol’ man river,

He jes’ keeps rollin’ along.

—OSCAR HAMMERSTEIN II, “OL’ MAN RIVER” (1927)

The headline was grim.

FIFTY-FOUR MIGRANTS DIE OF THIRST IN MEDITERRANEAN BOAT DRAMA.

Datelined Geneva, July 11, 2012, it recounted a horrific ordeal. Nearly five dozen migrants from Africa trying to reach Italy died of thirst when their inflatable boat ruptured in the Mediterranean, according to testimony from the sole survivor, Abbes Settou. The UN refugee agency UNHCR said that Settou, who drank seawater to survive, was spotted clinging to the remains of the stricken boat off the Tunisian coast by fishermen who alerted the coast guard. The man said there was no fresh water on board and people started to perish within days, including three members of his family.

It’s the cruelest irony to die of thirst while immersed in water.

It also highlights water’s critical importance. Of all the moving entities that surround and permeate our lives, the most vital are water and air—curiously, the only essentials that are transparent.

Our bodies are two-thirds water. Our brains are mostly made of it. No wonder these same brains enjoy watching it move as we dreamily stare at rivers and marvel at waterfalls. We bathe in water and jump into it at the slightest provocation; it’s the centerpiece around which vacations revolve. And, as with everything on this yin-yang planet, it sometimes turns on us, as my niece and Abbes Settou, sadly, learned.

Walls of water have always been terrifying. Yet aquatic fact and fiction competitively marched side by side for countless centuries. It took until passable science knowledge arrived in the nineteenth century before Noah’s flood went from literal truth to mere parable. This happened only when it became obvious that if every ounce of water vapor in the atmosphere precipitated as rain, it would raise the sea level by only a single inch. No need for an ark. Noah’s forty days of rain notwithstanding, floods, then as now, can never be more than regional events.

Still, the connection between water and humans may be even deeper than we suspect. Though generally ignored by anthropologists, the theory that Homo sapiens may be an aquatic ape linked genetically with lakes or the sea may explain such puzzles as our relative hairlessness, the size of our noses, and why we, unlike other primates, gasp when startled.1

In any event, Earth’s existence as a water planet, where 70 percent of the surface is liquid to an average depth of twelve thousand feet, is unique in the solar system. But it’s also logical, because H2O is the most common compound in the cosmos.

This, too, makes perfect sense. The universe’s most abundant elements are hydrogen, helium, and oxygen. Helium doesn’t combine with anything, so cross that off the “most important” list. And even though oxygen is a thousand times less prevalent than hydrogen, it’s always eager to join the party—any party. Small wonder that the H-and-O courtship and perennial “exchange of rings” is repeated in every corner of space and time.

Telescopes show water virtually everywhere. Steam envelops most stars. Comets are balls of dirty ice that turn into million-mile vapor streams, the stunning tail. Saturn’s rings, among nature’s grandest sights, are made up of countless chunks of ordinary ice.