Zoom: From Atoms and Galaxies to Blizzards and Bees: How Everything Moves (8 page)

Here’s the explanation that, guaranteed, nobody on your block knows.

When the current system was set in place in the 1950s, astronomers had been using earth-rotation data collected over the previous three hundred years. The official length of a day was codified in 1900. But during those centuries of observation, a day’s length slowly grew. Careful analysis now shows that a day was exactly 86,400 seconds long in 1820. Before that each day was shorter. Since then it’s been longer.

We generally labor under the illusion that 86,400 seconds make up a day. But this hasn’t been true for nearly two hundred years. A modern day is 86,400.002 seconds long. So we messed up. When the current system was put into place a half century ago, we could have then defined each second a little differently by adding a couple hundred more of those microwave beats to each official second. Who would care? Then our clocks would almost never need leap seconds. But we didn’t. So every year or two now, the little daily error accumulates enough so that we must take care of the accrued discrepancy.

To sum up, the real problem is not that Earth is slowing, which happens too gradually to matter much. It’s that each of our current days is longer than a day was in 1820, upon which our timekeeping system is, bewilderingly, based.

Because we foolishly designed the “second” around the 1820 data, we now need to compensate for the difference between a day now and a day when James Monroe was president. That means adding a second every five hundred days or so. It’s a “patch” to keep Earth-spin time and atomic-seconds time in agreement.4

As the Earth slows, the sun moves more leisurely across the sky. Its gradual slowdown is of course unnoticed in human lifetimes. Instead the dominant rhythm that affects us is its position in the sky. The sun is low and feeble during winter and high and fierce in summer. The daily light-darkness ratio—winter’s short days and long nights—is also critical. Other than that, most folks are oblivious to the sun’s motion. How many people even realize that throughout the Northern Hemisphere, in the United States, Europe, China, and so on, the sun always moves to the right? Meaning the sun rises diagonally upward to the right, then moves directly rightward at midday, and sets by slinking rightward into the western horizon.

Equatorial residents view something different. There the sun rises straight up until it gets overhead. Then, through the afternoon, it drops straight down like a lead ball. Because of this, it quickly buries itself below the horizon after sunset. Twilight in the tropics is always short. In the Southern Hemisphere, the sun moves leftward during the day. It’s a quick way of knowing where you are in case you’re ever shanghaied and wake up on another continent.

Can you handle one more solar oddity? Over the course of a year, day and night are not balanced. Thanks to our atmosphere, which bends light, the sun seems to sit on the horizon when it’s actually already set. At that point we see a ghost, a solar phantom. This air trickery, refraction, grants most locations seven minutes of extra daily sunlight. It’s why days and nights are not equal at the equinoxes: sun dominates.

This undeserved sunshine adds up. We enjoy forty extra hours of sunlight annually. The year is not even close to a fifty-fifty day-night mix.

On top of that, as we all know, sunset is never followed by sudden blackness. On the moon, yes, but not here. Refraction delivers its enchanting gift of twilight. Its brightest portion bestows yet another hour of useful light split between dawn and dusk.

The brightest afterglow is called civil twilight. Although it sounds vague, the term twilight is precisely, legally defined, dictated by the sun’s unseen motion below the horizon. In the evening it’s the interval between sunset and the time when the sun has sunk six degrees, or a dozen sun widths. Civil twilight lasts about a half hour in most places. At its conclusion, according to many municipal ordinances, streetlights must be on.5

But the bottom-line sun motion is its speed as it crosses the sky. Most people don’t know about angles or degrees, so let’s simply use the sun’s own width as a measuring tool. Think about all the sunsets you’ve watched. How long does it take the sun to move a distance equivalent to its own diameter? Or ponder the moon instead, which moves at the same visible speed. The answer:

Crossing the sky, the sun traverses its own width in exactly two minutes.

During a sunset, because the sun slides into the horizon at an angle, the interval from first contact to complete disappearance is about three minutes. This is right on the borderline of perceptible motion. The sun appears to move at the same speed as the minute hand of a kitchen clock when viewed from a few feet away.

Our final desert-motion phenom is its most renowned specialty: the mirage. As we all know, mirages are common on hot surfaces, such as a highway on a summer afternoon. The culprit is the changing speed of light. Despite its reputation as a constant, light travels more slowly through cool air. But the hot air above a summer road or broiling sand lets light move faster right there, closer to its vacuum speed, and this change bends, or refracts, images hitting it. The result is a mirror effect. The air reflects the sky, perfectly mimicking a puddle of water.

But finding any movement was an impossible job when I was in the desert. Nothing budged once those dust devils died. The absence of flowing water, moving clouds, circling birds, buzzing insects, or rustling leaves makes the desert visually frozen. A still photograph. Its landscape offers the antithesis of animation.

But later there came a few hot afternoon gusts. Bits of sand blew momentarily. The still life came alive. Clearly the dunes migrate over time. And when it comes to shifting sands, only one person is associated with their vagaries. British brigadier Ralph Alger Bagnold.

He was the archetypical English stiff-upper-lip, military-cum-Renaissance man. Bagnold was born in 1896, son of a derring-do colonel in the Royal Engineers who gloriously participated in the 1884–85 rescue expedition that attempted to free Major General Charles George Gordon from Khartoum. His sister was Enid Bagnold, who wrote the bestselling 1935 novel National Velvet.

Armed with this odd genetic pedigree, Bagnold attended Malvern College, joined the Royal Engineers, as his dad did, and received medals for serving in the miserable World War I French trenches for three years. After the war Bagnold studied engineering and earned a master of arts degree at Cambridge University. He returned to active duty in 1921 and then got swept into his lifelong calling. He served in Cairo and the Thar wastelands of northwestern India, and at both places he spent every spare minute exploring the desert.

Bagnold described his extensive excursions in his book Libyan Sands: Travel in a Dead World (1935). He developed a special type of compass that would not go awry around the iron ore often buried in arid regions. It was he who discovered that one really could drive a car across the Sahara as long as you let most of the air out of the tires and kept punching the gas pedal when the sands got deep. You got the feeling this was knowledge gained the hard way.

Although a third of the world’s deserts are covered with sand, there has been very little research into these ergs, as sand-covered desert areas are, oddly, called—probably because it’s hard to travel there or even reach many of them, and at that point it’s very slow going to make much physical progress. Bagnold changed that with his still-definitive book, published in 1941, The Physics of Blown Sand and Desert Dunes, which is every bit as tedious as it sounds. After the first two or three chapters I discovered that it is not a page-turner, despite the Amazon five-star rating that lured me to purchase it. But no one to this day has improved on its revelations. Bagnold used wind-tunnel experiments to predict sand movement and confirmed these expectations with extensive observations in the Libyan desert.

Basically, sand is characterized by its size rather than its composition. Bagnold defines sand as any particle between 0.02 millimeter and 1.0 millimeter in diameter, although later experts generously expanded the upper range by more than 50 percent, to 1.6 millimeters—a fifteenth of an inch. Size matters, because sand is defined as consisting of grains small enough to be moved by the wind but too heavy to remain in suspension in the air, as dust and silt do. Particles too heavy to be blown by wind are classified as pebbles or gravel. If it’s smaller than a thousandth of a millimeter, a particle essentially remains suspended in the atmosphere and scarcely falls at all. But then it’s called smoke or dust, not sand. It’s not rocket science.

Although sand can be composed of nearly anything, most of it is quartz, essentially because quartz is common and, Bagnold explained, “resistant to both mechanical and chemical breakup into smaller sizes.”

Wind, needless to say, is responsible for sand piling up into dunes and also for abrading and rounding each grain. (Sand beneath rivers and seas is another story, of course, because there water is the erosive force.) Because sand is two thousand times heavier than air, it doesn’t blow easily. It’s not house dust. No action at all is observed when the wind is less than ten miles per hour, which was my initial experience in the Atacama. But then, when the wind blows between ten and twenty miles per hour, lots of activity unfolds all at once.

The wind moves sand in two ways. The main method is called saltation, which is the picking up of grains. In this method the weight of the grains quickly brings them back down a short distance away. Carefully watching the process is like observing the quick hops of millions of kangaroos. The other transport method is called creep, in which wind rolls or bounces grains. In this method the grains typically move forward at about half the speed of the wind. Both courses of transport are in-your-face obvious if you spend time in a sandy desert on a breezy day. There’s really no other action to observe.

You’d also think—wandering among the endless dunes—there’d be no possible sound but the wind. That’s usually true. But on rare occasions the desert sings. Says Bagnold at the very end of his extensive sand-physics study:

We now pass from the squeaks made by small quantities of beach sand when trodden underfoot, to the great sound which in some remote places startles the silence of the desert. Native tales have woven it into fantasy… sometimes it is said to come upwards from bells still tolling underground in a sand-engulfed monastery; or maybe it is merely the anger of the jinn! But the legends… are hardly more astonishing than the thing itself.

Bagnold then shares his personal experience: “I have heard it in southwestern Egypt 300 miles from the nearest habitation. On two occasions it happened on a still night, suddenly—a vibrant booming so loud that I had to shout to be heard by my companion.”

The security and serenity of the dunes, Bagnold’s life’s obsession, had been suddenly replaced by spookiness. At the far end of the earth this scrupulous man of science was enveloped by irrational mystery. He knew that sounds are always caused by motion. But how on earth can dry sand create an earsplitting detonation or the equally bewildering “singing”?6

Dark horizontal markings on rock structures at Utah’s Lake Powell are boundary layers that once existed below the sea. Such long-term alterations in our planet’s appearance, unknown to classical thinkers, unfold too slowly for human perception.

Ultimately Bagnold admitted, seventy-five years ago, that these desert cacophonies are a mystery. The acoustic puzzle has persisted through the years despite being the subject of two recent TV specials. Bagnold did, however, notice that the bizarre booming or singing, which sometimes continued for more than five minutes, “always came from the lower part of a sand avalanche.”

After completing his epic study, Bagnold founded and was the first commander of the British Army’s Long Range Desert Group during World War II. He wrote scientifically useful papers through the 1980s before leaving Earth for the great cosmic desert in 1990 at the age of ninety-four.

My special time in the Atacama duly noted, I trudged back to the now-baking car and reached the fishing village in another hour. There I met upbeat people who spoke so slowly that even I could understand their Spanish. I hired a fisherman to take me out to see penguin colonies in a boat that looked only marginally seaworthy in the large swells, and with the engine off we sat quietly while several dolphins came to the starboard side, where we listened to them breathe. Glorious. But this was enough leisurely slow-mo time. Within a few days I made my way back to Santiago and a flight to the place where our world turns at its fastest rate.

I had a specific goal in mind: the unique events found only at the equator. What awaited me instead was a surprise.

Weird Goings-On at the Equator, and the Frenchmen Who Died Young

By heaven, man, we are turned round

and round in this world…

—HERMAN MELVILLE, MOBY-DICK (1851)

In Quito, perched at nearly ten thousand feet above sea level, the air is so thin that a visitor can scarcely walk two of its hilly blocks before stopping to catch his breath. I was here, very simply, because the capital of Ecuador is the world’s only city that sits right smack on the equator—where our planet’s spin hurls every pedestrian around the earth’s axis faster than it does anywhere else—1,038 miles per hour.1

Supposedly the equator also offers unique opportunities to witness Earth’s strange effects on moving water. Because human bodies and brains are mostly H2O, I wanted to see firsthand this relationship between our most intimate companions, the whirling world and swirling water. I’d heard that the Ecuadoran government had built a major museum precisely on the equator and that there were daily demonstrations.

The equator is more than merely the fastest-spinning place on earth, the place where the moon and stars whiz fastest through the sky. Thanks to the centrifugal force that makes Earth a bit like a carnival ride, people at the equator are partially lifted off our world, like those on the periphery of a high-speed carousel. A beefy man weighs a pound less in Quito than he does in Fairbanks, making it a potentially lucrative place for a weight-loss clinic guaranteeing instant results.