Magnetic north has never sat still. In the last hundred years or so, the direction in which our compasses steadfastly point has lumbered ever northward, driven by Earth's churning liquid outer core some 1,800 miles beneath the surface. Yet in recent years, scientists noticed something unusual: Magnetic north's routine plod has shifted into high gear, sending it galloping across the Northern Hemisphere—and no one can entirely explain why.

The changes have been so large that scientists began working on an emergency update for the World Magnetic Model, the mathematical system that lays the foundations for navigation, from cell phones and ships to commercial airlines. But then the U.S. government shut down, placing the model's official release on hold, as