FoundationalConceptsNeuroscience

Near the equator the vector’s direction is nearly horizontal and
parallel to the surface. The magnitude and direction of this geomag-
netic field provide information useful in navigation. We humans use
an instrument, a magnetic compass, to measure the direction of the
geomagnetic field.
Humans began to appreciate the navigational utility of Earth’s
magnetic field about a thousand years ago. For eons animals have
been moving long distances around the planet; many animals—in-
cluding birds, fish, and turtles—migrate these distances with great
accuracy. Some are known to return after journeying thousands of
miles to the exact same locations year after year. If humans during the
past few centuries have figured out how to build magnetic compasses
and use the geomagnetic field as a source of navigational information,
it certainly is the case that animals, given millions of years of evolu-
tionary time, have also figured out ways to do this.