The Food Lab: Better Home Cooking Through Science

out some invisible rays, and all of a sudden, your food is
cooked and hot. Must be magic, right?
The reality is far more benign. A microwave works by
sending out long waves of electromagnetic radiation that
create an oscillating magnetic field inside the chamber.
Because water molecules are polar—that is, they are sort of
like tiny magnets with a positive end and a negative end—
the oscillating magnetic field causes them to rapidly jostle
up and down. It’s the friction that this jostling water creates
that in turn heats up your food. That’s why a microwave
won’t affect objects that don’t contain water or some other
magnetic molecules.
But hold on, back up. Electromagnetic radiation. Isn’t that
like, all dangerous and stuff? Well, sure, certain types of it
are dangerous. But EM radiation (as we’ll refer to it from
now on) comes in many forms. Indeed, the very light that
you see coming from the sun, from a flashlight, or from the
quiet glow of your iPad is a form of EM radiation. It just
happens to be of a wavelength that your eyes can detect.
(That’s right—your head has radiation detectors built right
into it.) Radio waves are another form of EM radiation. The
X-rays a doctor shoots at your chest when you accidentally
swallow a lobster whole when eating too fast are a more
dangerous form of EM radiation. Even the heat from an
oven or a red-hot poker is EM radiation. It’s everywhere,
but again, not all radiation is dangerous. Microwaves fall
squarely into the “nondangerous” category. At least, so long
as you don’t try and stick yourself behind the shielded door
of the cooker.
That said, the microwave has some severe limitations as a