Microwaves can transform a frozen pizza into hot, melted
goodness in four minutes flat, but they can’t rescue your melted
ice-cream sundae. To cook food, a microwave oven converts
voltage into high-frequency electromagnetic microwaves. The
molecules in food—especially water and fat—absorb this energy
and wiggle at high speeds, causing them to heat rapidly and warm
the surrounding food. Although quickly turning leftovers cold
would be handy, this is a one-way operation, explains David
Pozar, a professor and microwave expert at the University of
Massachusetts. Microwaves can only speed up atoms, not slow them
down. Scientists do have a high-tech method for slowing atoms,
however: lasers. Shoot a moving atom with a laser, and it will
absorb the laser’s photons and re-emit them every which way,
causing the atom to hold nearly still. Placing an atom at the
junction of multiple beams can slow its momentum in all
directions, decreasing its energy and cooling it. This drops an
atom’s temperature a couple hundred degr