the sky, it will fly straightaway back to its home. So reliable is this
behavior that pigeons have been used since ancient times to carry
messages from one place to another and have also been selectively
bred to enhance their rapid flight home after release in a distant place.
A classic series of experiments conducted around 1970 demonstrated
that a small magnet affixed to the body of a pigeon severely interfered
with its ability to navigate home on cloudy days—days where the
sun’s location was not visible. Decades later, the sensory structure
with which pigeons and other animals detect the geomagnetic field
is still not known. Various hypotheses have been suggested, among
which are the alignment of tiny magnetic particles known to occur in
pigeons and other animals, and magnetic effects on the alignment of
electron spins in certain light-activated molecules in the bird’s eyes.
Another sweet mystery.
Electric and magnetic fields, very low- and very high-frequency
sounds, ultraviolet and infrared radiation, light polarization—these
things are not perceivable by humans, at least as far as we know. In ad-
dition, some animals have more sophisticated odor detection than we
do, others have more refined color vision, and still others have better
visual acuity. The world as experienced by animals having sensory-
perceptual abilities different from our own is likely to differ in sig-
nificant ways from the world as we know it. What is it like to be a fish
living in the murky waters of the Amazon, communicating with other
fish via oscillating electric fields and detecting the presence of nearby
objects by electroreception?
Glowing and pulsing,
microwaves radiating—
from pocket and purse.