Until the arrival of GPS, the magnetic compass was the single most useful navigational tool available to humans. But it’s a recent invention. Although Chinese explorers understood the principles of the compass earlier, it entered service in Europe in the 12th century.
Other animals have been magnetic navigators for much, much longer. Many different species—ranging from newts and insects to sea turtles, fish, and birds—are able to orient themselves relative to the Earth’s magnetic field. Among mammals, naked mole rats, deer, and even dogs also seem to have this gift. Researchers have recently shown that the brainwaves of human beings respond to changes in magnetic fields, though it’s far from clear whether or not we can make any navigational use of this effect.
But how all these different species actually detect the Earth’s magnetic field remains largely mysterious.
We know that certain bacteria that respond to magnetic fields carry within ...
