The Wild File
Your urgent inquiries about the world, answered
By Hampton Sides

I've heard that the magnetic North Pole is moving! Is my 1950 compass out-of-date?
— Mel Saltaine, Ojai, California

The more we learn about the capricious ways of our planet, the more we discover that those concepts we revere for their sense of permanence and order are only shadowy readings of a world in flux. Witness the geomagnetic field, which, far from being stable, can be a wildly idiosyncratic force.

Suffice it to say, the magnetic North Pole is indeed shifting, thanks to the perpetual sloshing around of molten iron in Earth's liquid core. These days, magnetic north — ground zero for the planet's conductive fluids and the "N" to which our compasses point — can be found at latitude 79.8 degrees north and longitude 106.8 degrees west, which puts it in the Peary Channel, off Canada's Sverdrup Islands. Scientists at the U.S. Geological Survey who track its migration tell us that it has been pinballing around the Arctic Circle for some 750,000 years, at one point straying as far as 30 degrees southward, about the equivalent of Anchorage. Currently, however, it's sliding northwest at a couple of miles a year.

So how does all this polar freewheeling affect the precision of an antique compass? Not at all. Your 1950 model can locate magnetic north as accurately as a new one. Maps, however, are a different story: All charts are oriented toward geographic north, but only the most reliable make allowances for declination (the discrepancy between geographic and magnetic north) by including calculations that enable you to adjust your compass heading. Refer to an old map and chances are the declination figures will be obsolete — a surefire way to get yourself lost. Which explains why the USGS updates its maps every five years and why it's always wise to check the vintage of yours. The good news? Most handheld GPS devices are programmed to adjust automatically to the whimsical nature of magnetic north. But not so their high-tech brethren: GPS units installed in planes must undergo a fine-tuning every 28 days.

This may sound goofy, but are elephants really afraid of mice?
— Stacy Sadler, Honolulu, Hawaii

From the bizarre-but-true department: Six-ton elephants really do shy away from some members of the rodent world. Despite what the cartoonists at Disney would have you believe, however, it's nothing personal. The long-nosed pachyderms have no atavistic dread of mice — they just have crummy vision. Because an elephant's eyes are set on the sides of its enormously broad head, it is unable to focus at close range and thus is easily startled by small, unidentified objects skittering underfoot. Alarmed, it recoils its trunk and commences stomping the interloper with its cement-block-size feet — at which point you can bet it's the rodent who's running scared.

What makes snow squeak when you walk on it?
— Ann Franklin, St. Louis, Missouri

At times like this, it's comforting to know that there are people in the world who spend large amounts of time peering through microscopes at dainty flakes of snow. What we've learned from these glaciologists is that in particularly chilly temperatures — roughly 20 degrees Fahrenheit or colder — soft, wet snowflakes harden into abrasive ice crystals. That high-pitched crunching noise is the collective sound of thousands of these granules colliding when compressed under the weight of your foot. As the temperature rises, the flakes' molecular structure becomes flexible and a lubricating layer of water develops, leaving us with a stoic substance that — no matter what kind of boot-stomping duress we put it under — won't emit so much as a squeal.