Instead, he deduced that the faint hiss had to be coming from somewhere in the center of the Milky Way. At the age of twenty-six, Jansky had made a historic discovery. As a physicist, Jansky understood that all forms of energy waves passing through the universe, including light, were electromagnetic waves of varying lengths. All are generated when atoms and molecules collide with each other, forming waves, much as a stone tossed into a pool of water forms waves. One of the characteristics of long radio waves that differentiate them from visible light waves is that they can be heard but not seen. Therefore, Jansky concluded that bodies deep in space could and did emit invisible light rays as well as visible ones.

Light waves that are characterized by a particular range of electromagnetic wavelengths between seven hundred...