Zoom: From Atoms and Galaxies to Blizzards and Bees: How Everything Moves (14 page)

We’re used to this. But Aristotle, on one of his bad hair days, insisted that air exerts no weight on us at all. And Galileo, normally the iconoclast, meekly accepted Aristotle’s incorrect call without argument.

This was the airy mind-set into which Evangelista Torricelli was born, in Faenza, part of the Papal States, in 1608. He’s another unsung hero, virtually unknown today, even though he was the one who figured out why the wind blows.

Torricelli lost his father at the age of four. He was raised and educated by an uncle and studied mathematics at a Jesuit college. When he was twenty-four he read Galileo’s Dialogue Concerning the Two Chief World Systems and wrote to the great man, telling him that he, too, believed in the Copernican sun-centered model. It was a quick way to get on the irritable man’s good side.

Torricelli didn’t know it yet, but that was a perilous opinion to commit to in writing, given that Galileo was condemned by the Vatican the next year, 1633, and nearly burned at the stake for that very belief. No Jesuit could safely afford to ally himself with such heresy, and Torricelli remained silent thereafter.

The bearded Galileo, soon a prisoner under house arrest, invited Torricelli to visit him, and Torricelli accepted, though it took him five judicious years before he showed up at the door. It was around this time that he started to make scientific breakthroughs in understanding the air and brainstormed inconclusively with Galileo about a very puzzling issue brought up by yet another Italian mathematician and astronomer, Gasparo Berti.

Between 1639 and 1641, Berti experimented with long vertical glass tubes more than three stories tall, filled with water, which had both ends plugged with corks. The bottom end was placed in a pool of water and its stopper removed. What happened next produced the head-scratching.

Some water drained out into the pool, but most of it stayed in the tube. At a height of thirty-five feet—three and a half stories—the water’s surface settled a little to leave an empty space in the top of the cylinder. The issue was why the water always remained piled up that high.

The long column of enclosed water always stopped draining when it was thirty-five feet tall, never significantly more or less. Galileo believed the vacuum at the top had enough sucking power to hold up the weight of all that water, the way a milk-filled straw remains full as long as you keep your finger over one end.

But in 1644 Torricelli hit on a different explanation. What if it wasn’t the vacuum sucking and holding the water up but rather our atmosphere’s weight pressing down on the pond that supported the water? In other words, perhaps the apparatus was like a balance. Maybe it weighed the air above the pond, whose downward pressure was exactly sufficient to keep aloft a thirty-five-foot-high water column. He noticed another oddity, too: the level changed from day to day, going up or down by about a foot.

Berti and Torricelli kept ordering these custom-made, frustratingly fragile four-story glass cylinders and had carpenters build special openings in their homes to let them poke skyward, while others followed their experiments with interest. What the heck did it really mean? A century earlier those suspended water columns would have represented a simple oddity of nature, one of thousands that earned no more than shrugs. But in seventeenth-century northern Italy, nature’s foibles had become mesmerizing. They beckoned like some fabled El Dorado, pregnant with the promise of revealing profound underlying secrets.

Those tubes. Those freaking unwieldy glass tubes. They were causing Torricelli’s neighbors to whisper “witchcraft.” He’d already dodged a bullet with his ally Galileo, but he could still get in trouble. Anxious to end all the staring at his strange through-the-roof straws, and already experimentally filling his tubes with heavier liquids, including honey, Torricelli had a brainstorm for a truly portable device that could be hidden from prying eyes. Because liquid mercury—quicksilver, as it was then called—weighs fourteen times more than water, a tube of that liquid metal could be relatively short and still be useful for his experiments. Torricelli then filled a tube with a mercury column that stood only about thirty inches high and placed it in a pan that was also filled with liquid mercury, thus creating the first barometer.

Its level varied from day to day by as much as an inch, and Torricelli correctly surmised that the weight of air pushing on the mercury pool in the pan must change by about three percent. The way it varied was intriguing, too. The mercury tended to stand highest on cool, clear days and lowest when the weather was stormy.

The French mathematician and physicist Blaise Pascal heard about Torricelli’s apparatus in 1646, along with the furor over what, exactly, was keeping those columns of water and mercury standing so strangely erect. Was it the vacuum in the tube pulling or the atmosphere outside the tube pushing down the liquid in the pan or pond? Pascal had a brainstorm, a way to find out once and for all.

If air had weight, there’d be less of it as a person ascended a mountain. Logically, a barometer in an elevated location would display a lower quicksilver column. Was that true? Pascal asked his brother-in-law, who lived in the hills, to perform this decisive experiment. In September of 1648, the height of a mercury column was noted at the base of the Puy de Dôme and then periodically during the ascent to the summit. Bingo: the barometer got lower the higher one went. And not by a little, either. It wasn’t subtle. The mercury plummeted a full inch for each thousand feet of ascent. At the top of the 4,800-foot mountain, the mercury stood 24.5 inches tall instead of the twenty-nine inches seen at the base.

Case closed. Not only did Pascal prove the weight of the atmosphere, he also effectively created an altimeter, a way to find one’s elevation. Today, newer models using dry diaphragms instead of mercury grace every airplane cockpit.

In 1644 Torricelli wrote the famous line: “We live submerged at the bottom of an ocean of elementary air, which is known by incontestable experiments to have weight.” He also soon delivered the world’s first scientific description of the cause of air motion: “Winds are produced by differences of air temperature, and hence density, between two regions of the earth.”

Torricelli went on to design and build microscopes and telescopes but did not live long enough to gain world renown. Just three years after Pascal had proved him right, he contracted typhoid fever in Florence and died at the age of thirty-nine.

But his invention became all the rage. As we’ve seen, humans are quick to perceive patterns, and the daily rises and falls of barometers were intriguingly linked with the approach of sunny and rainy weather respectively. It was a forecasting device!

Everyone wanted one. By 1670, many clock makers started producing them for wealthy patrons. A century later, most upper-class homes prominently displayed ornate wooden barometers decorated with magnificent inlaid designs. There were more than 3,500 registered barometer makers in the Western world between 1670 and 1900.

Around 1860, the British admiral Robert FitzRoy, former captain of the Beagle, on which Darwin made his famous voyage, started publishing forecasting instructions linked to changes in barometric pressure. He explained newly discovered intricacies. For example, he found that unusually strong barometric highs and lows as well as rapid pressure changes are often followed by wild winds as air frantically tries to go from a high-pressure to a low-pressure region. From that point on, all mariners obsessively consulted barometers before embarking on voyages of any length. Such was the importance of changing air pressure.5

Today we’re aware of a fascinating cornucopia of pressure events. As you travel to a new location higher above sea level, the temperature falls by around five degrees per thousand feet of climb. This is huge. It means that Denver, up at five thousand feet, is fully twenty-five degrees cooler, on average, than a sea-level city at a comparable latitude.

Dwarfing a cruise ship is a shelf cloud of a thunderstorm. Beneath it, winds often hit fifty miles per hour.

Thanks to the compression of lower air layers by the weight of everything above, exactly half the atmosphere lies below eighteen thousand feet. A barometer therefore falls to half its sea-level reading when at that height.

Want to feel what it’s like up there? You can get close. The highest you can easily ascend and still have your feet on the earth is not in Europe or the United States but in South America. I went there in 1988. First you fly into the Venezuelan city of Mérida, snuggled in the Andes in the westernmost part of that country, where you’re already a mile high. Then you go to an amazing cable car that takes your breath away as you dangle a zillion miles above nothingness. It vertically climbs an astonishing ten thousand feet—equal to nine Empire State Buildings stacked one atop the other. You go up and up, swaying with every breeze, until you reach 15,629 feet. Now you’re on the top of Pico Espejo, a stone’s throw from the summit of the famous Pico Bolívar, the highest point in Venezuela, a mere seven hundred feet higher.

In aviation classes they teach pilot trainees that some people feel the effects of altitude at a mere five thousand feet—after all, few small planes are pressurized. Because the blood of people who live or spend a week or more at high altitudes has far more red blood cells than that of people at sea level—unless you are conditioned as well as the Hulk and have a major upgrade over his presumed blood composition—your arrival at Pico Espejo will make you instantly dizzy and maybe euphoric. Walking more than a couple of steps will be exhausting. Here you can perform high-altitude experiments if you can remember what you were doing from one minute to the next. Yet this lofty, picturesque perch in the Andes is still some two thousand feet below the half-atmosphere threshold.

A handful of Himalayan mountaineers have gone way beyond that and experienced even Mount Everest’s 29,035 feet without supplemental oxygen. But they, of course, are pretty much space aliens.

Forget about climbing. If we stay with the lazy concept of simply driving as high as possible, there are a few places outside of Leh—in northwestern India, north of the Himalayas—where the pothole-ridden dirt road goes through passes that are seventeen thousand feet high. Still not quite at that magical eighteen-thousand-feet, halfway-to-outer-space milestone. For that there is supposedly a motorable pass called Suge La, west of Lhasa, Tibet, situated at 17,815 feet, and at Semo La, at 18,258 feet, between Raka and Tsochen in central Tibet. Let me know if you ever do it. You probably will not need E-ZPass.

As you ascend to any new height, wind speed generally increases, and the boiling point of water drops by roughly 1.5 degrees for each thousand feet. It adds up. Sherpas simply shrug and serve tepid tea, because water boils off before it can get very hot.

With the advent of truly high-altitude balloons and, especially, rocket-mounted instruments, the discoveries got weirder. In the 1950s, scientists learned of a frightening point called Armstrong’s line. (No relation to Neil, the first man on the moon. It is named after Harry George Armstrong, who commanded the United States Air Force’s School of Aviation Medicine at Randolph Field, near San Antonio, Texas, between 1946 and 1949.) Pegged at between 62,000 and 63,500 feet, or twelve miles high, it is the elevation at which water boils at body temperature. There, exposed body fluids—such as those in your eyes, your saliva, and any blood outside pressurized veins and arteries—simply boil away. This isn’t good for you.

As for high-altitude air motion, during every preflight check when I fly my own plane, I use a great aviation resource, the National Weather Service’s Aviation Digital Data Service (http://aviationweather.gov/adds/winds/), to check how the current wind increases at various heights. Right now in Ohio it’s calm at the surface. But the wind blows at twenty miles per hour at three thousand feet, whistles at thirty-five miles per hour at six thousand feet, screams at 115 miles per hour at twenty-four thousand feet, and blows a tornado-like 180 miles per hour at thirty-six thousand feet.

That’s the jet stream. It’s a strange, narrow cylinder of superfast westerly winds that exists on several other planets, too. Its discovery unfolded when scientists watching the skies after the famous 1883 eruption of the Krakatoa volcano saw high-altitude ash whizzing toward the east at tremendous speed. They called this phenomenon the equatorial smoke stream. Then in the 1920s, Japanese meteorologist Wasaburo Oishi detected identical high winds going eastward from Mount Fuji and released balloons to track it. But it took World War II aviators to confirm that, indeed, if your plane runs into a jet stream, it can speed up by as much as two hundred miles per hour. This helps explain why a coast-to-coast flight in the United States is an hour shorter when heading eastward. The jet makes the trip using 20 percent less fuel. Strangely enough, airlines don’t offer a discount for flights in that direction.

I finally reached the Presidential Range, in northern New Hampshire, one of the least populated areas east of the Mississippi. I turned into the entrance to the park and paid my fee. There I learned that one’s car had better be in good shape to make the climb up Mount Washington, and the brakes better be good enough to make the unrelenting descent, and some models were simply not allowed: you had to have an operational first gear, for example, which eliminated some Lincoln Continentals. But I did, so I stepped on the gas, and my Solara convertible whined against the incline, tackling a road built in 1861.

I did not hit the mountain at the right time. I had no chance to witness people being blown off their feet. In August, when I was there, the summit’s average wind speed of twenty-four miles per hour is only about half what it is in January, which is when things get crazy. Five of Mount Washington’s Januarys have seen gusts higher than 170 miles per hour—the same as the strongest-level hurricane. But it’s never happened in summer. This was a place of extremes, but where was my dramatic story?

A hurricane-force gust blows a scientist off his feet at the observing station atop New Hampshire’s Mount Washington, the windiest place in the Northern Hemisphere. (Mount Washington Observatory)