Джеймс Глик - Genius - The Life and Science of Richard Feynman

Matter would crumple in on itself. Only in terms of quantum mechanics was that impossible, because it would give the electron a definite pointlike position. Quantum-mechanical uncertainty was the air that saved the bubble from col apse.

Schrödinger’s equation showed where the electron clouds would find their minimum energy, and on those clouds depended al that was solid in the world.

Often enough, it became possible to gain an accurate picture of where the electrons’ charge would be distributed

in the three-dimensional space of a solid crystal lattice of molecules. That charge distribution in turn held the massive nuclei of the atoms in place—again, in places that kept the overal energy at a minimum. If a researcher wanted to calculate the forces working on a given nucleus, there was a way to do it—a laborious way. He had to calculate the energy, and then calculate it again, this time with the nucleus slightly shifted out of position. Eventual y he could draw a curve representing the change in energy. The slope of that curve represented the sharpness of the change—the force. Each varied configuration had to be computed afresh. To Feynman this seemed wasteful and ugly.

It took him a few pages to demonstrate a better method.

He showed that one could calculate the force directly for a given configuration, without having to look at nearby configurations at al . His computational technique led directly to the slope of the energy curve—the force—

instead of producing the ful curve and deriving the slope secondarily. The result caused a smal sensation among MIT’s physics faculty, many of whom had spent enough time working on applied molecular problems to appreciate Feynman’s remark, “It is to be emphasized that this permits a considerable saving of labor of calculations.”

Slater made him rewrite the first version. He complained that Feynman wrote the way he talked, hardly an acceptable style for a scientific paper. Then he advised him to submit a shortened version for publication. The Physical Review accepted it, with the title shortened as wel , to

“Forces in Molecules.”

Not al computational devices have analogues in the word pictures that scientists use to describe reality, but Feynman’s discovery did. It corresponded to a theorem that was easy to state and almost as easy to visualize: The force on an atom’s nucleus is no more or less than the electrical force from the surrounding field of charged electrons—the electrostatic force. Once the distribution of charge has been calculated quantum mechanical y, then from that point forward quantum mechanics disappears from the picture. The problem becomes classical; the nuclei can be treated as static points of mass and charge.

Feynman’s approach applies to al chemical bonds. If two nuclei act as though strongly attracted to each other, as the hydrogen nuclei do when they bond to form a water molecule, it is because the nuclei are each drawn toward the electrical charge concentrated quantum mechanical y between them.

That was al . His thesis had strayed from the main line of his thinking about quantum mechanics, and he rarely thought about it again. When he did, he felt embarrassed to have spent so much time on a calculation that now seemed trivial and self-evident. As far as he knew, it was useless.

He had never seen a reference to it by another scientist. So he was surprised to hear in 1948 that a controversy had erupted among physical chemists about the discovery, now known as Feynman’s theorem or the Feynman-Hel mann theorem. Some chemists felt it was too simple to be true.

Is He Good Enough?

A few months before graduation, most of the thirty-two brothers of Phi Beta Delta posed for their portrait photograph. Feynman, seated at the left end of the front row, stil looked smal er and younger than his classmates.

He clenched his jaw, obeyed the photographer’s instruction to rest his hands on his knees, and leaned gravely in toward the center. He went home at the end of the term and returned for the ceremony in June 1939. He had just learned to drive an automobile, and he drove his parents and Arline to Cambridge. On the way he became sick to his stomach—from the tension of driving, he thought. He was hospitalized for a few days, but he recovered in time to graduate. Decades later he remembered the drive. He remembered his friends teasing him when he donned his academic robe—Princeton did not know what a rough guy it was getting. He remembered Arline.

“That’s al I remember of it,” he told a historian. “I remember my sweet girl.”

Slater left MIT not many years after Feynman. By then the urgency of war research had brought I. I. Rabi from Columbia to become the vigorous scientific personality driving a new laboratory, the Radiation Laboratory, set up to develop the use of shorter and shorter radio wavelengths for the detection of aircraft and ships through night and clouds: radar. It seemed to some that Slater, unaccustomed to the shadow of a greater col eague, found Rabi’s presence unbearable. Morse, too, left MIT to take a

Rabi’s presence unbearable. Morse, too, left MIT to take a role in the growing administrative structure of physics. Like so many scientists of the middle rank, both men saw their reputations fade in their lifetimes. Both published smal autobiographies. Morse, in his, wrote about the chal enges in guiding students toward a career as esoteric as physics.

He recal ed a visit from the father of a graduating senior named Richard. The father struck Morse as uneducated, nervous merely to be visiting a university. He did not speak wel . Morse recal ed his having said (“omitting his hesitations and apologies”):

My son Richard is finishing his schooling here next spring. Now he tel s me he wants to go on to do more studying, to get stil another degree. I guess I can afford to pay his way for another three or four years.

But what I want to know is, is it worth it for him? He tel s me you’ve been working with him. Is he good enough to deserve the extra schooling?

Morse tried not to laugh. Jobs in physics were hard to get in 1939, but he told the father that Richard would surely do al right.

PRINCETON

The apostle of Niels Bohr at Princeton was a compact, gray-eyed, twenty-eight-year-old assistant professor named John Archibald Wheeler who had arrived the year before Feynman, in 1938. Wheeler had Bohr’s rounded brow and soft features, as wel as his way of speaking about physics in oracular undertones. In the years that fol owed, no physicist surpassed Wheeler in his appreciation for the mysterious or in his command of the Delphic catchphrase: A black hole has no hair was his. In fact he coined the term “black hole.”

There is no law except the law that there is no law.

I always keep two legs going, with one trying to reach ahead.

In any field find the strangest thing and then explore it.

Individual events. Events beyond law. Events so numerous and so uncoordinated that, flaunting their freedom from formula, they yet fabricate firm form.

He dressed like a businessman, his tie tightly knotted and his white cuffs starched, and he fastidiously pul ed out a pocket watch when he began a session with a student (conveying a message: the professor wil spare just so much time …). It seemed to one of his Princeton col eagues, Robert R. Wilson, that behind the gentlemanly façade lay a perfect gentleman—and behind that façade another perfect gentleman, and on and on. “However,”

Wilson said, “somewhere among those polite façades

there was a tiger loose; a reckless buccaneer … who had the courage to look at any crazy problem.” As a lecturer he performed with a magnificent self-assurance, impressing his audience with elegant prose and provocative diagrams.