If I move a block of stone into the green-wood sector of the bagua, will my children grow up to be dull? If I put my desk next to a window, will my thoughts become insipid? Where is the dragon sleeping? Practitioners of feng shui, the Chinese art of geomancy, worry about such things—and not least whether in calculating the most propitious placement of a building, the orientation should be to magnetic north or to true north.
North, to a proto-Indo-European traversing the steppes a few thousand years back, was simply the direction the left hand pointed in when one faced the rising sun, a position that changed throughout the year. Our notion of north is based on a finer but still inexact science, its core assumption that we live on a perfect orb that spins along at a uniform rate. We do not, and it does not. Still, true north is a geometric concept that posits a line, a meridian, wrapping neatly around the planet. Also called geodetic north, it is constant to the extent that, for our lifetimes, it points pretty much toward Polaris, our North Star for the next few thousand years.
True north, in other words, does not really exist in nature. Neither does grid north, a term used in mapmaking to account for the difference between north on a presumed round Earth and north on a flat map. In most places the variations between true and grid north are minor, but substantial enough that they’re noted on modern maps. Astronomic north is formally calculated from the vertical direction of gravity and the axis of rotation of the planet, and not, as is true north, from its presumed roundness; the difference between astronomic and geodetic north is called the Laplace’s correction, used mostly by surveyors.
Among all the different norths, including record and assumed, the most important, if only because the most real, is magnetic north. Consult a compass, and unless weird circumstances obtain, the point toward which the needle freely spins is the north magnetic pole, the place—now geodetically north of Canada’s Axel Heiberg Island—where the planet’s northerly magnetic field intersects with the surface. This pole wanders by tens of miles each year, yielding a cartographic problem that cries for constancy. Thus, presto, the polite fiction of geodetic and grid norths.
True north and magnetic north, the differences between which are measured by an angle of declination, are the same only here and there on the planet, including points along an agonic line that stretches from the Gulf of Mexico to the Arctic and that for much of its southern course more or less coincides with the Mississippi River valley. Another is said to lie within the eerie area called the Bermuda Triangle, a place of many navigational errors and not a few shipwrecks and downed planes.
If you travel there, you don’t have to bother changing your iPhone’s compass setting to “Use true north,” as you might want to do elsewhere in your wanderings. Just watch the reefs. Or, elsewhere, the Guernseys, since cows seem to have an uncanny propensity for aligning themselves toward geomagnetic north as they browse. Call it bovine feng shui.