Beyond the God Particle by Leon M. Lederman, Christopher T. Hill
Authors: Leon M. Lederman, Christopher T. Hill
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Hastings-on-Hudson, Dobbs Ferry, Tarrytown. On a particular Friday afternoon, January 5, 1957, my mind was occupied with the lunchtime conversation led by Columbia's leading theoretical physicist and gourmet, Professor Tsung Dao Lee. The issue was an experiment suggested some months earlier by Lee and his Princeton colleague, Frank Yang. The experiment was designed to test a centuries-old idea in a new domain of physics. The old idea was a belief in the symmetry between the real world and the mirror world. It had long been believed that the mirror reflections of real world processes were also real world processes. Look in the mirror. A man's jacket has its buttons on the right side of the coat. In the mirror, the buttons appear to be on the left side. But there is no law against securing the buttons on the left side.
Which side gets the buttons is a matter of convention. Similarly, turning a screwdriver clockwise (as judged by the guy turning the screwdriver) advances the screw further into the block of wood. This is a “right-handed” screw, of course. By convention, screws are right-handed. The mirror image of the process makes the screw look left-handed. But again, there is no law that prevents you from going to the manufacturer and ordering left-handed screws. They may charge you too much, but the law of mirror symmetry says it can be done and experience confirms it.
Mirror symmetry has vast implications in science. It is the same as the bilateral symmetry of the human body and of so many animals. Draw a vertical line down the center of a face and the two halves are mirror images. Molecules in which the atoms have a specific three-dimensional structure often have mirror images, which have different chemical behaviors; chemists and biologists are intensely interested in these mirror relations, but in all cases, the basic symmetry, i.e. the mirror world, obeys the same laws of physics, chemistry, and biology as the real world. Until January 6, 1957.
And until Lee and Yang had published a paper questioning whether the mirror image of radioactive processes obey mirror symmetry. What makes radioactive processes different from buttons, screws, and biological molecules, is that radioactivity is a signature of the “weak force.” Certain puzzling reactions seen in the study of weak force driven decays would make sense if the weak force did not respect the symmetry. Incidentally, the validity of weak force symmetry (in the spirit of Emmy Noether's theorem) gives rise to a conservation law: the Law of Conservation of Parity. Parity is a measure of the “handedness” of a system.
Earlier in the summer of 1950, Lee and Yang had suggested a number of processes that could be studied in order to verify mirror symmetry, or to disprove the symmetry. C. S. Wu, a Columbia colleague and a skilled experimenter and expert on radioactive decays, had decided then to attempt one of the experiments which involved the radioactive decay of Cobalt 60.
The talk at our weekly Chinese lunch was that Wu had been recently seeing some interesting data, that the effect she was observing indicated a failure of mirror symmetry and that the effect could be large.
It was this information that kept circulating in my head: “A large effect?” Back in August 1956 physicists collected at the Brookhaven Laboratory, conveniently situated near some of the finest ocean beaches bordering Long Island's Atlantic shore—summers at Brookhaven were a favorite for family fun and for more serious physics discussions. Hearing Lee and Yang's proposal that perhaps mirror symmetry may fail if we concentrate on only those processes controlled by the weak forces—those that produce radioactive decays—was a revelation.
The idea sparkled for two reasons. The first was that this could explain some data that seemed totally contradictory—where 99 and 7/8ths of all reactions rigorously obeyed mirror
Which side gets the buttons is a matter of convention. Similarly, turning a screwdriver clockwise (as judged by the guy turning the screwdriver) advances the screw further into the block of wood. This is a “right-handed” screw, of course. By convention, screws are right-handed. The mirror image of the process makes the screw look left-handed. But again, there is no law that prevents you from going to the manufacturer and ordering left-handed screws. They may charge you too much, but the law of mirror symmetry says it can be done and experience confirms it.
Mirror symmetry has vast implications in science. It is the same as the bilateral symmetry of the human body and of so many animals. Draw a vertical line down the center of a face and the two halves are mirror images. Molecules in which the atoms have a specific three-dimensional structure often have mirror images, which have different chemical behaviors; chemists and biologists are intensely interested in these mirror relations, but in all cases, the basic symmetry, i.e. the mirror world, obeys the same laws of physics, chemistry, and biology as the real world. Until January 6, 1957.
And until Lee and Yang had published a paper questioning whether the mirror image of radioactive processes obey mirror symmetry. What makes radioactive processes different from buttons, screws, and biological molecules, is that radioactivity is a signature of the “weak force.” Certain puzzling reactions seen in the study of weak force driven decays would make sense if the weak force did not respect the symmetry. Incidentally, the validity of weak force symmetry (in the spirit of Emmy Noether's theorem) gives rise to a conservation law: the Law of Conservation of Parity. Parity is a measure of the “handedness” of a system.
Earlier in the summer of 1950, Lee and Yang had suggested a number of processes that could be studied in order to verify mirror symmetry, or to disprove the symmetry. C. S. Wu, a Columbia colleague and a skilled experimenter and expert on radioactive decays, had decided then to attempt one of the experiments which involved the radioactive decay of Cobalt 60.
The talk at our weekly Chinese lunch was that Wu had been recently seeing some interesting data, that the effect she was observing indicated a failure of mirror symmetry and that the effect could be large.
It was this information that kept circulating in my head: “A large effect?” Back in August 1956 physicists collected at the Brookhaven Laboratory, conveniently situated near some of the finest ocean beaches bordering Long Island's Atlantic shore—summers at Brookhaven were a favorite for family fun and for more serious physics discussions. Hearing Lee and Yang's proposal that perhaps mirror symmetry may fail if we concentrate on only those processes controlled by the weak forces—those that produce radioactive decays—was a revelation.
The idea sparkled for two reasons. The first was that this could explain some data that seemed totally contradictory—where 99 and 7/8ths of all reactions rigorously obeyed mirror
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