Zoom: From Atoms and Galaxies to Blizzards and Bees: How Everything Moves (6 page)

The planet’s rapid slowdown at higher latitudes soon gets out of hand. Fairbanks spins at just 422 miles per hour. It’s zero at the pole. You’d just stand there nearly motionless, like an idiot, pivoting too slowly for anyone to notice, facing the opposite way twelve hours later.

Since 90 percent of all humans live in the Northern Hemisphere, let’s surrender to our boreal bias, apologize to our Aussie, Kiwi, South African, and South American friends, and focus on the North Pole for the sake of brevity. You reach it by heading due north from anywhere. Reindeer do not live there. No one does. It lies in the Arctic Ocean, which used to be frozen all the time but nowadays is open water during the summer, when the kids are home.

Becoming the first person to reach that spot was once the most prestigious thing you could possibly do. A century or so ago it would make you an instant Neil Armstrong. The problem was that, with no communication with the outside world and no humans within a thousand miles, you and whomever you could talk into joining the party would be utterly on your own. Even if you could somehow contact the Royal Geographical Society’s help line and reach a real person in a cubicle, you can imagine how thrilled they’d be with your problem.

“Hmm. Remember Beardley? Seems he’s trapped in the ice two thousand miles northwest of Iceland. Wants to know if we can send someone to fetch him. Yes, right away.”

Henry Hudson, itching for more adventures after discovering the river that Sully Sullenberger eventually landed in, managed to come within seven hundred miles of the North Pole in 1607. This was an amazing accomplishment for the time. (In the spring of 1611, on an ensuing polar expedition to find the fabled northwest passage to China, his crew mutinied and put Hudson, his teenage son, and a few others off in an open boat into what we now call Hudson Bay. They were never seen again.)

A few Russian and British explorers managed to inch a few miles closer during the next two centuries, but not by much. The race heated up, if that’s even the right word, in the late nineteenth century, when the American James Booth Lockwood and his sledding party got farther north than anyone before him. He died in April of 1884, at the age of thirty-one, during a miserable three-year expedition, two months before a rescue party arrived. He reached latitude 83°24′30″, just 450 miles short of the goal.

Two years later, the rhyming Norwegian explorers Nansen and Johansen reached latitude 86°14′ north on skis and dogsled from the ship Fram, which had been caught and held as if by a vise in drifting ice in the Arctic Basin. They were forced to stop a mere two hundred miles short.

The North Pole was finally attained on April 6, 1909, by the American Robert Peary, who succeeded by dogsled. The South Pole was conquered just two years later, in December of 1911, by the expedition of the Norwegian Roald Amundsen. A month later, the pathetic Brit Robert Scott arrived; his infamous quest not only failed to get him there first but cost the lives of the entire party, thanks to the brutal bad luck of hitting the coldest weather in a decade.

These explorers reached poles that are not nailed in place. Despite their reputation as the steadier of the two types of poles (it’s the magnetic poles that are moving like crazy), these geographic poles do shift back and forth. It isn’t much; there’s a deviation of only about forty feet per year from the average position. The maximum movement is barely over one hundred feet. However, because astronomical and geodetic measurements, not to mention deeds and survey maps, are based on the latitude and longitude system—those horizontal and vertical lines on maps and charts, pinpointing every pond, home, and used-car lot on the planet—and because polar shifts throw these numerical positions slightly out of whack, the variations gather a lot of attention and are constantly monitored.

To obtain accurate information about polar motion, the International Latitude Service was established in 1899; it was renamed the International Polar Motion Service in 1961. Nowadays the ongoing quest is handled by the International Earth Rotation Service. You want to know what our planet is up to? They’re the ones who will tell you. The service’s outposts are dedicated to making continual observations of latitude changes (and rotation hiccups and lots of other arcane stuff). They update the precise coordinates of the geographic poles all the time. This is a serious group, whose members grab the phone and say, “Are you sitting down? You won’t believe this!” if the poles unexpectedly shift a foot, as they do after some major events, such as tsunamis.

The geographic, or physical, poles only “jump” following an especially violent earthquake that redistributes the mass on our spinning globe. More usually, their motion consists of just two smoothly changing components. There’s a circular shift called the Chandler wobble, which completes a cycle every 433 days, or 1.2 years, and there’s an annual movement that goes back and forth in seemingly random directions. The annual component varies from year to year, though it’s always less than fifty feet.

Why does Earth do this? Theories have come and gone for centuries. There’s no hard evidence for anything. One favorite notion was that Earth’s oval orbit makes the solar gravity stronger in January than in July. Nowadays we think it’s due to seasonal redistributions of ice and air masses.

And the Chandler wobble? Named for the American Seth Chandler, who discovered this planetary gyration in 1891, it was finally explained 110 years later, in 2001. Richard Gross of the Jet Propulsion Laboratory, using computer simulations, produced a persuasive analysis showing that most of the 433-day wobble comes from changing pressures on the ocean floors caused by variations in temperature and salinity. Salt shifts the poles! The rest of Chandler wobble results from atmospheric fluctuations.

The geographic poles (a.k.a. the physical poles, or the rotational poles) have never shifted significantly, at least not since the moon’s creation four billion years ago. And they never will. You could walk across each pole’s greatest positional change in twenty seconds.

Obviously, when people speak fearfully of the poles shifting, they can’t mean the geographic poles. In reality, most folks don’t even know which poles worry them. It’s been too many years since earth science. If you ask them, “Which poles do you mean—the geographic or the magnetic?” you’ll likely get a blank stare.

A major sudden shift in the geographic poles would create global destruction, but it’s never happened and is physically impossible. So enough about them.

Time, then, for the poles that don’t just wander in circles a few dozen feet, like my mother-in-law searching for her parked car. We come now to the animated poles.

These are the places where compasses point.

Sloshing liquid iron three thousand miles below the surface, moving around the solid iron ball that sits at Earth’s center like an olive pit, generates a rather wimpy magnetic field. (Our planet’s field averages about 0.5 gauss on the magnetism scale. By comparison, a strong refrigerator magnet is 100 gauss.) Even when a magnetic sliver is balanced on a needle so that it can swivel at the slightest provocation, it only feebly aligns north. There’s not much oomph in our planet’s magnetism—unlike the magnetism on, say, Jupiter.

Here’s a bit of arcana known only by your college physics professor: Earth’s south magnetic pole is the one that’s located in the far north. (A south magnetic pole is one in which the field lines go down, toward Earth’s center.) But to keep our citizens in their normal, happy, unconfused state we call this one the North Magnetic Pole, and I have no problem with that. It’s located in the north, and that’s good enough to merit the label.

As kids, when we’d sprinkle iron filings over paper with a magnet placed beneath it, we’d see the distinctive curving shapes of the magnet’s field. And, similarly, Earth’s magnetic field lines run horizontally over most of the planet and then dive straight down at the, ahem, North Pole. So a magnetic pole is simply where field lines are aligned up and down. But you don’t have to bother trying to visualize magnetism angling into the ground. There’s a simpler way to find that “vertical-field-lines” place: compasses point there.

Does it matter where the North Magnetic Pole is located? Not really. Auroras form a glowing green ring around the place, and they’re beautiful. People in Fairbanks would be sorry to see it migrate too far. But other than that, if it shifts position it affects nothing and no one.

Good thing, too. The North Magnetic Pole is in constant motion, though it has dwelled in Canadian territory since at least before the days of Galileo and Shakespeare. It currently sits five hundred miles from the pole of rotation. That’s closer together than the two competing poles—geographic and magnetic—have been at least since English sounded like anything intelligible to modern ears.

The North Magnetic Pole actually drifted south during the seventeenth and eighteenth centuries until it sat at latitude 69° north, barely in the Arctic at all. Then it started going north. Its location at Ellesmere Island was first discovered by explorer James Clark Ross in 1831. A century ago its northerly motion started accelerating and inexplicably grew from five miles to thirty-seven miles a year. Nowadays the North Magnetic Pole is just west of Ellesmere, the planet’s tenth-largest island, where only 140 winter-sports-loving people live, most of them in the Canadian military. They like to boast that they’re the most northerly group of humans in the world.

During the last century the North Magnetic Pole has berserkly sped a whopping 650 miles almost due north, so that it’s now passing latitude 84° north. It moves twenty-two feet an hour!

In the ocean, it recently crossed Ellesmere’s two-hundred-mile territorial limit, which means the North Magnetic Pole no longer belongs to the Canadians. It was one of their claims to fame, and they’re not happy about this development. First they have a bad maple syrup year, and now this.

If the pole keeps going in the present direction, it will shoot clear across the Arctic Ocean and down the other side into Siberia by the time today’s teenagers start bleaching off their tattoos, around midcentury.

The Buddha preached equanimity—that we should stop having opinions about absolutely everything. Well? Should anyone care about this? Does it matter whether these poles stay put or wildly scamper to a new spot? Here’s why some people do indeed care.

Two or three times each million years, on average, Earth’s entire magnetic field reverses its polarity. In other words, if you were alive a million years ago, and facing what we call north with a compass in your hand, the needle would point to the south. No matter that you and I can’t even sense Earth’s magnetism in the first place. Nor can most animals.3

The idea of a “pole flip” sounds dramatic and worrisome, but actually the science behind it is very cool.

We’ve only known about magnetic reversals since 1959. They weren’t easy to detect at first, because there hasn’t been a single one for the past 780,000 years. Turns out, however, that when lava containing ferrimagnetic minerals solidifies, its iron bits line up with Earth’s prevailing magnetic field. This happens as soon as the lava cools below its Curie temperature of 1,414 degrees Fahrenheit, or 768 degrees Celsius. So we can read these rocks as though they were a novel.

Researchers dug deeper and excitedly turned the pages. Here was a reversal, and here, and here, until they’d unearthed 184 polarity reversals in the last eighty-three million years.

These pole flips were some sort of strange new motion cycle. And you know how we humans love patterns and trying to see if they sync up with others. If it were Christmas, these rhythms would be fabulous puzzle toys tied up with ribbons.

But as we unwrapped each one, it became increasingly clear that the poles reverse randomly. There is no rhyme or reason. No pattern. Using radiometric dating, we found that the North and South Poles changed position every 450,000 years on average. But sometimes they’d flip rapidly. A little less than two million years ago there were five reversals in a mere million years. Another time there were seventeen in a three-million-year period. The rock records even revealed a case of two flips in fifty thousand years.

Each geomagnetic period is called a chron. In between chrons, there is a transition phase: it takes between ten thousand and one hundred thousand years for the new polarity to establish itself. Contrary to today’s paranoid news reports, a magnetic pole reversal was never something that unfolded while you were having a latte. If a pole reversal had begun during the Last Glacial Maximum, when New York’s Central Park lay submerged beneath a mile of ice, the reversal would still not be fully established today.

Researchers also found two or three superchrons, a period when the same magnetic alignment lasted more than ten million years. The Cretaceous Superchron endured for forty million years. An earlier one had lasted fifty million years.4 Their causes are anyone’s guess. Who can fathom what exactly is going on 1,800 miles beneath the surface, where the liquid outer core begins? Analysis of seismic echoes provides a crude picture of Earth’s interior layers, and we can only hope that future refinements will let us understand the hows and whens of magnetic-field production and reversals. One thing is certain: epic patterns of uncountable tons of moving liquid iron are responsible, and they have their own natural animation. The reversals certainly do not correlate with major meteor impacts, sea-level fluctuations, or any other sporadic global events we can find. Nor do they match up with our planet’s orbital shifts or changing axial tilts, which, being recurring and predictable, would have resulted in regular rather than random polarity shifts.

The only real concern has been the state of our magnetosphere during the process. What if our field temporarily vanished? Isn’t that our protection against cosmic radiation? Would that roast earthly life and afflict us with runaway mutations and cancers? This remains the basis for the current near hysteria in some overcaffeinated circles.

The scientific answer: there’s no problem. If they were truly harmful, reversal periods would match up with times of mass extinctions. They don’t. The fossil record shows that pole flips never affect the biosphere. Those weren’t even periods of sudden appearances of new life-forms. Evolution wasn’t being prodded in those interchron periods.