It was Isaac Newton, guiding a beam of light through a prism, who first discovered that white light was a mixture of many colors. Next scientists found that light consisted of waves, and the length of the wave determined the color.

But red and violet were not the ends of the spectrum. More experiments showed that beyond red were waves that we could not see, but could feel as heat. And beyond violet were shorter waves.

What caused all these waves? How could we measure them? What can we do with them?

In their laboratories, scientists found that the waves can help us “see” to the depths of the oceans and through the clouds. We can cook foods, send messages, and even find out how the universe began by studying invisible waves. Read how it all happened!

One of the “energy” “How Did We Find Out” books (including, of course, How Did We Find Out About Energy? itself), this one concentrates more heavily on physics and astronomy than one might expect. That is, it does mention microwave ovens but only briefly (and doesn’t even have a picture of one!), which is odd considering that most children today are bound to say “oven” in a free-association test including the word “microwave.” Still, microwaves do enough in physics and astronomy to justify the attention Asimov gives them. Older readers might find books like Understanding Physics, Volume Two more useful as an introduction to microwaves, but younger readers should find this volume well worth while.