137 - Arthur I. Miller [119]
Pauli firmly believed that principles of symmetry had to prevail. The way to find them lay not only through logic, but in the more irrational dimensions of thought. “With me the mixture of mysticism and mathematics, which finds its main results in physics, is still very dominant,” he wrote.
Two decades earlier Pauli had argued with Bohr when Bohr suggested that the law of the conservation of energy might not entirely hold in the case of beta-decay. It was to preserve this law that Pauli had proposed the existence of the neutrino. As we have seen, the neutrino had been discovered in the laboratory six months earlier and played a role in Wu’s experiment. It is one of the most weakly interacting particles of all.
“[Bohr] was wrong with the energy law, but he was right that the weak interactions are a very particular field where strange things could happen, which don’t happen otherwise,” Pauli wrote. He added that physicists should bear in mind something else Bohr had said: “We have to be prepared for surprises.” Pauli himself was willing to speculate that in interactions much weaker than the weak interactions, not just parity but energy too might not be conserved (that is, the amount of energy involved at the start of a process is not the same as at the end). “‘Be prepared for surprises’ not anywhere but specifically with the beta-decay,” he wrote.
Pauli had met Chien-Shiung Wu in 1941 when he visited the University of California at Berkeley and described her to Jung as impressive, “both as an experimental physicist and an intelligent and beautiful Chinese young lady.” Born in Shanghai in 1912, she had come to America in 1936 and worked first at Berkeley before moving to Columbia. Photographs show her formidable intelligence as well as her beauty. She was a perfectionist—just the person needed to attempt the highly precise experiment to test parity.
Pauli wrote to her that “what had prevented me until now from accepting this formal possibility [of parity violation] is the question why this restriction of mirroring appears only in the ‘weak’ interactions, not the ‘strong’ ones.” But what did the strength of an interaction have to do with a law of conservation? The question has still to be answered. “In any case, I congratulate you (to the contrary of myself),” he added. “This particle neutrino—on which I am not innocent—still persecutes me.”
“God is a weak left-hander after all,” he wrote exuberantly to Jung. A neutrino only spins in one direction. If one looked at it in a mirror, it would still spin in the same direction. Most screws are right-handed—you twist the screwdriver in the same direction as the curl of the fingers on your right hand and turn the screw toward your right thumb. Neutrinos are left-handed in that they spin in a direction opposite to their motion, the direction in which you would twist a screwdriver for a left-handed screw. So God is a left-hander, but a weak one, because he is only a left-hander in the weak interactions—featuring the neutrino—where parity is violated.
The Chinese woman
Pauli could not fail to notice what a supreme example of synchronicity this was. A Chinese woman had played an important part in his dreams, particularly those involving mirrors and their reflections; and a Chinese woman had carried out the critical experiment that brought about the downfall of parity—that is, of mirror symmetry—in physics. He wrote to Jung of his “shock” at this “‘Chinese revolution’ in physics.”
Fierz told him he had “a mirror complex.” “I admitted as much,” Pauli wrote to Jung. “But I was still left with the task of acknowledging the nature of