Genius_ The Life and Science of Richard Feynman - James Gleick [217]
No wonder his colleagues found their nerves jangling as they tried to write problem sets. Before a half-year was gone, he was teaching an uncompromising version of the geometry of relativistic space-time, complete with particle diagrams, geometrical transformations, and four-vector algebra. For college freshmen this was difficult. Along with the mathematics Feynman tried to convey a feeling for how he visualized such problems, placing his “brain” into his diagrams like Alice plunging through the Looking-Glass. He tried to make his students imagine the apparent width and depth of an object:
They depend upon how we look at it; when we move to a new position, our brain immediately recalculates the width and the depth. But our brain does not immediately recalculate coordinates and time when we move at high speed, because we have had no effective experience of going nearly as fast as light to appreciate the fact that time and space are also of the same nature.
The students were sometimes terrified. Yet Feynman also returned to the standard fare of an introductory physics course. When he covered centers of mass and spinning gyroscopes, experienced physicists realized that he was giving the students not just the mathematical methods but also original, physical understanding. Why does a spinning top stand upright on your fingertip and then, as gravity pulls its axis downward, slowly circle about? Even physicists felt they were learning the why for the first time when they heard Feynman explain that the gyroscope began by “falling” an invisibly small distance … (He did not want to leave the students thinking a gyroscope was a miracle: “It is a wonderful thing, but it is not a miracle.”)
No realm of science was out of bounds. After consulting with experts in other fields, he gave two lectures on the physiology of the eye and the physiochemistry of color vision, making a profound connection between psychology and physics. He described the view of time and fields that arose from advanced and retarded potentials, his graduate work with Wheeler. He delivered a special lecture on the principle of least action, beginning with his high-school memories of his teacher Mr. Bader—how does a ball know what path to follow?—and ending with least action in quantum mechanics. He devoted an entire lecture to one of the simplest of mechanical gadgets, the ratchet and pawl, the sawtoothed device that keeps a watch spring from unwinding—but it was a lesson in reversibility and irreversibility, in disorder and entropy. Before he was done he had linked the macroscopic behavior of the ratchet and pawl to the events occurring at the level of its constituent atoms. The history of one ratchet was also the thermodynamic history of the universe, he showed:
The ratchet and pawl works in only one direction because it has some ultimate contact with the rest of the universe… . Because we cool off the earth and get heat from the sun, the ratchets and pawls that we make can turn one way… . It cannot be completely understood until the mystery of the beginnings of the history of the universe are reduced still further from speculation to scientific understanding.
The course was a magisterial achievement: word was spreading through the scientific community even before it ended. But it was not for freshmen. As the months went on, the examination results left Feynman shocked and discouraged. Still, when the year ended, the administration pleaded with him to keep on for a second year, teaching the same students, now sophomores. He did, finally trying to teach a thorough subcourse in quantum mechanics, again reversing the conventional order. Another Caltech physicist, David Goodstein, said long afterward, “I’ve spoken to some of those students in recent times, and in the gentle glow of dim memory, each has told me that having two years of physics from Feynman himself was the experience of a lifetime.