Zoom: From Atoms and Galaxies to Blizzards and Bees: How Everything Moves (16 page)

It has recently, of course, fallen out of popular use. In modern times, one never hears anyone say, “Look outside: there’s a strong breeze of Beaufort force six.” And on the rare occasions when Beaufort’s highest number dramatically envelops your neighborhood in eolian violence, you’d think “hurricane” rather than “Beaufort force twelve.”

I’ve nonetheless heard those exact words at sea. In 2006, when I was the astronomy lecturer on a month-long Holland America cruise around South America, our ship hit crazy winds as we approached Tierra del Fuego, at the bottom of Chile. We were inside the famous roaring forties, the name given to the routinely strong westerlies between latitude 40° south and latitude 49° south. Although no Pacific storm had been forecast, the winds just kept growing and growing until the captain made the announcement, “The winds are now Beaufort force twelve.”

The ship rose and fell crazily. The piano slid across the library and smashed into the wall. Dishes kept crashing. Staying in one’s cabin provided little relief: you slid down your bed from the disconcertingly steep seesaw bow-to-stern tiltings. I have it all on video. I went up on deck, which was totally empty except for the rare crewman who stepped out to gawk. Several told me that they’d never before been in a hurricane at sea until then. The waves looked just like Francis Beaufort’s descriptions. Swells reached up to my eye level, seven stories above the sea. These were seventy-foot waves.

Yet everyday winds can be just as exciting when you’re attuned to them. Here are the Beaufort numbers, along with the more useful miles-per-hour equivalents and—most important—how you can tell what’s what.

Beaufort force 0 means no wind. The official description is “calm.” Smoke rises vertically. Water is mirrorlike. Foggy nights are often like that.

Beaufort force 1 is officially termed “light air.” The speed is 1–3 mph (1–5 km / hr). Rising smoke drifts. Weather vanes still don’t budge. Small ripples appear on water surfaces, but these ripples have no crests.

Beaufort force 2, officially termed a “light breeze,” has a speed of 4–7 mph (5.6–11 km / hr). Now you readily feel the wind on your skin. Leaves rustle, but no branches move. Weather vanes begin to turn. Small wavelets develop, but their crests are glassy, not rough.

Beaufort force 3 is a “gentle breeze,” with winds of 8–12 mph (12–18 km / hr). Leaves and small twigs move constantly. Lightweight flags extend. Large wavelets appear, with breaking crests and a rare whitecap.

Beaufort force 4 is a “moderate breeze,” with winds of 13–17 mph (20–28 km / hr). Dust and loose paper is lifted. Small branches begin to move. Small waves appear with many whitecaps.

Beaufort force 5 is a “fresh breeze,” with winds of 18–24 mph (29–38 km / hr). Medium-size branches move. Entire small trees sway if they’re in leaf. Most waves have whitecaps, and there is some spray.

Beaufort force 6 is a “strong breeze.” Winds are blowing around 25–30 mph (39–49 km / hr). Large tree branches move. Telephone and overhead electric wires begin to whistle. Umbrellas are difficult to keep under control. Empty plastic garbage bins tip over. Large waves form; whitecaps and spray are prevalent.

Beaufort force 7 is a “moderate gale.” Winds blow at 31–38 mps (50–61 km / hr). Large trees sway. Walking requires some effort. The sea heaps up. Some foam from breaking waves is blown into streaks along the wind direction.

Beaufort force 8 is a “gale.” Winds are 39–46 mph (62–74 km / hr). Twigs and small branches get broken from trees and litter the roads. Walking is difficult. Moderately large waves form, with blowing foam.

Beaufort force 9 is a “strong gale,” with winds of 47–54 mph (75–88 km / hr). Some large branches snap off trees. Large trees sway wildly. Temporary signs and barricades blow over. High, twenty-foot waves produce rolling seas and dense foam that reduces visibility.

Beaufort force 10 is a “storm” or “whole gale.” Winds roar at 55–63 mph (89–102 km / hr). Weak trees are blown down or uprooted. Saplings are bent and deformed. Weak or old asphalt shingles are peeled off roofs. Large waves of 20–30 feet have overhanging crests. There is a heavy rolling of the sea, which is white with foam. Visibility is reduced.

Beaufort force 11 is a “violent storm,” with winds of 64–72 mph (103–117 km / hr). There is widespread damage to trees and crops. Many trees are blown over. Many roofs are damaged. Many objects left unsecured are blown away and can break glass. The sea has very high waves of 37–52 feet and extensive foam, and there is restricted visibility.

Beaufort force 11 winds of around seventy miles per hour are slightly below hurricane strength but have easily destroyed half the trees in this forest.

Beaufort force 12 is a “hurricane.” Winds are above 72 mph (above 118 km / hr). Crops, plants, and trees suffer widespread damage. Some windows may break; mobile homes and weak sheds and barns are damaged. Heavy debris is hurled about. Waves are huge; over 50 feet. The sea is completely white with foam and spray. Visibility is negligible, thanks to driving spray.

I’m offering the entire Beaufort scale for one reason only: because to recognize what is happening and be able to label it means that you can watch air motion with more attention. And better observation creates better enjoyment. This way if you see branches swaying yet large tree trunks are steady, and overhead wires are whistling, and your plastic garbage pail just blew over, you can say with confidence: “Hey, honey, there’s a strong breeze outside. The wind is between twenty-five and thirty miles per hour.” And you’ll earn a perfunctory nod from your spouse, who really doesn’t care.

No matter. You and your fellow nature lovers are enraptured by the magic of the wind. And perhaps reminded of Alhazen, who figured out a thousand years ago where it ends. And of Evangelista Torricelli, whose words still linger:

“We live submerged at the bottom of an ocean of… air.”

Enigmas of the Most Far-Reaching Force

The whole damn thing, the universe,

Must one day fall.

—HOWARD NEMEROV, “COSMIC COMICS” (1975)

We take for granted the tinkle of falling rain. And we stick to Earth’s surface without giving it a thought. Yet can anyone honestly explain gravity or claim to know what’s going on? The otherwise perspicacious cultures of the ancient Greeks, Chinese, and Mayans didn’t even try.

Even today, how many of us ever really pay attention to the act of falling? Any kid who has belly flopped into a swimming hole knows that the higher the dive, the more it hurts. That’s because the farther up we jump from, the faster we hit the water. In fifth grade they used to cite thirty-two feet per second per second as the rate at which a plummeting body accelerates, until primary school science switched to the metric system, and then it became 9.8 meters squared. Too bad. We might have paid attention if they’d expressed it in everyday language.

Fall for a single second and you hit the ground going twenty-two miles an hour. Simple.

Each additional second you’re airborne makes you land another twenty-two miles an hour faster. Still simple.

If you want to stay in the air for exactly one second, you have to jump from a height of sixteen feet. One and a half stories. If you land on a trampoline this might not hurt. But you should not, as they say on TV, try this at home. To stay aloft for two seconds, however, means leaping from a six-story roof, and you’d then accelerate to forty-four miles an hour, the impact from which is usually not survivable. So humans, unlike squirrels, have a very narrow available range of safe falling. One second of plummeting can sometimes be okay. Two seconds means death.1

This is the hard-nosed reality all people and animals confront from the moment they take their first baby steps. Our motions are a contest between our muscles and the ground beneath us, as it eternally holds us as closely as possible.

As we’ve seen, Aristotle and his friends tackled downward motion by saying that everything made of the elements water and earth wants to fall. In a straight line. After all, a stone tossed off a cliff angles more and more toward a linear trajectory with every second it keeps plummeting.

Watching the sky, the ancients decided that up in the heavens, objects want to move in circles. The sun and moon daily circle around us. The stars nightly wheel around the North Star.2

Moreover, the only celestial objects that aren’t dots are the disks of the sun and moon—more circles. Clearly, the gods like circles in their realm. You can’t blame them. The circle, according to the Greeks, is the perfect geometric form—so perfect it was divine, with a legacy that lingers to this day in traditions such as the exchange of rings at weddings and engagements. It’s the only shape whose boundary contains no special points or direction changes and whose edge is at every point equidistant from the center.

So according to the Greeks, all motion is either linear or circular. Circular up there, linear down here. There was no word for gravity. There wasn’t even the concept of a downward-pulling force. Instead, objects themselves “want” to head downward and will do so the moment obstacles are removed.

That’s how things stood for century after century while children tripped and scraped knees and old men idly threw pebbles into ponds.

It took until modern times for this gravity business to become central to space exploration and bungee jumping and such. Meanwhile the parallel topic of air resistance developed into a major study of its own. It’s a central tenet of aircraft engineering and parachuting and was always a design feature in the animal kingdom—which explains why cats and squirrels usually never accelerate to lethal speeds no matter how far they fall.3

All that technological fun stuff was still to come when the ancient Greeks were alive. But when the sixteenth century dawned, science was dealing with old Greek views that had since been incorporated into Church dogma and was trying to make those square Plato-idea pegs fit into the round holes of actual planet movement.

The problem was that the holes were not round. They were oval. To chart planetary motion against the background stars was to observe loopy trajectories that didn’t jibe with anything circling a stationary Earth. Then in the sixteenth century, nightly observations performed meticulously for twenty years by the obsessive Danish astronomer Tycho Brahe refined the length of the year to within an accuracy of one second, which proves he was a type-A fanatic who refused to “round off” anything. He was good. Yet he failed to unlock the simplest underlying secrets of celestial choreography.

It did not appear as if planets moved in circular paths. But Tycho assumed all sorts of comically jury-rigged systems—planets moving in circles around empty spots of space that in turn orbited still more circles that then circled us—to preserve the traditional Holy Roundness. And to keep a motionless Earth at the center of it all. All his mental gymnastics, a pathetic purgatory of years of intellectual labor, served the single desperate purpose of trying to make the universe jibe with the clergy’s mistaken view of natural motion.

When Tycho died in 1601, his assistant, Johannes Kepler, inherited his notes and pondered them for the next ten years, right through and beyond Galileo’s first telescope discoveries in 1610. Kepler, a brilliant mathematician, came to a startling conclusion. The celestial minuet made sense only if the sun lay at the center of all motion, and the planets—including Earth—moved in elliptical paths.

Ellipses were not sexy, then or now. But they are the fact of the cosmos. They are the way gravity makes nearly all celestial bodies move.

Understanding ellipses is easy if you draw one. Push two thumbtacks partway into a piece of plywood or cardboard and loosely put a loop of string around them. Insert a pencil within the loop, pull it firmly sideways, and you’ll draw an ellipse. In the actual universe, each of those tacks is called a focus, and the sun occupies one focus of every planet’s orbit. (The other is just an empty spot of space. This bothers some people, who feel that such a vital mathematical point merits more than mere vacuity. Well, perhaps some enterprising space-travel company will someday erect a floating café there with a catchy name like the Focal Point.) This is the simple and complete reality of every planet’s path through space.

Kepler found that each planet speeds up as it approaches the sun in its oval path but decelerates as it heads away. Holy cow: Earth and all other worlds continually change their speeds. Nobody had seen that coming.

Obviously, something about the sun pulls on the planets. It was a puzzle pondered at that same time—the opening decade of the seventeenth century—by Galileo Galilei.

Galileo, who, like Kepler, was a longtime subscriber to Heliocentrism Today, decided to study the way things move and fall. He built ramps that had various kinds of slopes, set balls rolling, and watched what happened. He timed things carefully and concluded that, regardless of how steep or gentle the slopes were or how high a ball was when it was released, it would speed down one incline and then up another until it reached the same height as the one from which it was dropped.

If the second ramp was perfectly flat—horizontal—the rolling ball would just keep going and finally stop only, Galileo correctly determined, because of friction. He was struck by an amazing thought. Maybe the moon and planets were rolling sideways, too. In which case they’d continue in motion forever, which is exactly what they appear to be doing.

He used simple math, and the numbers added up as long as planets were not slowed down by any air resistance. They must be orbiting in a realm of emptiness!

These days we’re accustomed to the idea of space being a vacuum. But back then, “nothing” had a long, bumpy history in philosophy and never came out smelling like a rose. The Greeks, for example, made many intriguing arguments as to why nothingness was impossible, while Renaissance clergymen reasoned that “God is everywhere, so there can be no vacuum.”4

Galileo, in the opening years of the seventeenth century, became the very first person who was sure he knew what existed “up there” in the heavens. Nothing.