Genius_ The Life and Science of Richard Feynman - James Gleick [9]
In the 1920s, a generation before the coming of solid-state electronics, one could look at the circuits and see how the electron stream flowed. Radios had valves, as though electricity were a fluid to be diverted by plumbing. With the click of the knob came a significant hiss and hum, just at the edge of audibility. Later it was said that physicists could be divided into two groups, those who had played with chemistry sets and those who had played with radios. Chemistry sets had their appeal, but a boy like Richard Feynman, loving diagrams and maps, could see that the radio was its own map, a diagram of itself. Its parts expressed their function, once he learned to break the code of wires, resistors, crystals, and capacitors. He assembled a crystal set, attached oversized earphones from a rummage sale, and listened under the bedcovers until he fell asleep. Sometimes his parents would tiptoe in and take the earphones off their sleeping boy. When atmospheric conditions were right, his radio could pull in signals from far away—Schenectady in upstate New York or even station WACO from Waco, Texas. The mechanism responded to the touch. To change channels he slid a contact across a wire coil. Still, the radio was not like a watch, with gears and wheels. It was already one step removed from the mechanical world. Its essential magic was invisible after all. The crystal, motionless, captured waves of electromagnetic radiation from the ether.
Yet there was no ether—no substance bearing these waves. If scientists wished to imagine radio waves propagating with the unmistakable undulating rhythm of waves in a pond, they nonetheless had to face the fact that these waves were not in anything. Not in the era of relativity: Einstein was showing that if an ether existed it would have to be motionless with respect to any and all observers—though they themselves moved in different directions. This was impossible. “It seems that the aether has betaken itself to the land of the shades in a final effort to elude the inquisitive search of the physicist!” the mathematician Hermann Weyl wrote in 1918, the year Feynman was born. Through what medium, then, were radio waves sweeping in their brief journey from the aerials of downtown New York to Feynman’s second-story bedroom in a small frame house on the city’s outskirts? Whatever it was, the radio wave was only one of the many sorts of oscillations disturbing every region of space. Waves of light, physically identical to radio waves but many times shorter, crisscrossing hectically; infrared waves, perceptible as heat on the skin; the ominously named X rays; the ultra-high-frequency gamma rays, with wavelengths smaller than atoms—all these were just different guises of one phenomenon, electromagnetic radiation. Already space was an electromagnetic babel, and human-built transmitters were making it busier still. Fragmented voices, accidental clicks, slide-whistle drones: strange noises passed through one another, more waves in a well-corrugated waviness. These waves coexisted not in the ether but in a rather more abstract medium, the precise nature of which was posing difficulties for physicists. They could not imagine what it was—a problem that was only mildly allayed by the fact that they had a name for it, the electromagnetic field, or just the field. The field was merely a continuous surface or volume across which some quantity varied. It had no substance, yet it shook; it vibrated. Physicists were discovering that the vibrations sometimes behaved like particles, but this just complicated the issue. If they were particles, they were nonetheless particles with an undeniably wavelike quality that enabled boys