Radiation: the Pure Energy of Radiant Heat and Microwaves

We all know that the earth is warmed by the sun. How does solar energy reach us across millions of miles of nearly empty space, where there’s nothing there to conduct or convect? The answer is thermal radiation, a process that does not require direct physical contact between heat source and object. All matter emits thermal radiation all the time, though normally we can detect it only when something is very hot. The warmth we feel from sunlight or a stove burner comes from thermal radiation. It’s emitted by atoms and molecules which, having absorbed energy, release it again not in the form of faster movement, but as waves of pure energy.