Back in the 1930s, when physicists were just starting to get used to the new mathematics of the quantum theory, Lev Landau, a russian physics professor, proposed a new conservation law. It was a law of conservation of symmetry which said, in simple form, that the dynamics of a quantum reaction would be the same whether you were looking at the reaction itself or a mirror image of that reaction. That seemed to make sense according to all the experiments that had been done and, more importantly, it explained why some reactions that conserved energy and mass weren’t observed. So everybody immediately said that because nature was symmetric that obviously ought to be true and it was called “The Law Of Conservation Of Parity” and everybody believed in it. Nobody had the slightest smigin of doubt about it: the conservation of parity was so obvious.
Fast forward twenty-plus years. Professor Lee Tsung-Dao of Columbia University and Professor Yang Chen-Ning of the Institute of Advanced Study in Princeton were studying the peculiar behavior of a certain meson. It seemed to have two modes of decay. That wasn’t unusual in itself, but the two modes had different values of parity. If the Law of Conservation of Parity held, that shouldn’t happen. So either we had two mesons with different parity that otherwise looked so much alike we couldn’t tell the difference between them (which was unlikely) or the “Law of Conservation of Parity” didn’t hold (which was unthinkable).
Lee and Yang thought hard and figured out two experiments that could be performed that would have different results if parity was or was not conserved. They were not easy experiments. One involved the measurement of the relative angular distribution of beta and gamma radiation from polarized radioactive nuclei. The nuclei had to be kept still, which meant holding them at around absolute zero in temperature. That required a facility that was capable of detecting beta and gamma radiation from a sample held at cryogenic temperatures.
The other involved the measurement of the angular distribution of the decay of a pi meson into a mu meson and the subsequent decay of that mu meson into an electron. That was not only difficult but it required access to a relatively high energy accellerator.
I happened to be present when Lee and Yang presented this discussion (in greater scientific detail) as a seminar to the Physics Department of Columbia University. It went over like a lead baloon. Not only did all the attendants (possibly including Lee and Yang) firmly believe in the Laws of Physics including the conservation of Parity, but the experiments were very difficult and, if they got negative results, would not be suitable for publication because everybody expected that they would get negative results. The consensus (with the exception of Lee and Yang) was that it was interesting to know there had been no direct experimental proof of the conservation of parity in weak interactions, but it wasn’t interesting enough to risk their professional reputations on a wild goose chase.
Lee and Yang then went to Professor Wu Chen-Shung who was a world class experimenter in the area of beta decay. They didn’t think they could convince her to do the experiment, so they asked if they could borrow enough equipment to do it themselves. She told them that because they were theoreticians they couldn’t be trusted with her precious equipment, but she’d consider doing the experiment if she could recruit a cryogenic partner to handle the low temperature aspects. She was turned down by the low temperature facility at Columbia, but she convinced the cryogenic lab at the National Bureau Of Standards to provide her with facilities. After some considerable difficulty, she succeeded in getting some data that shown an agreement with Lee and Yang’s suggestion. It seemed possible that Parity was not conserved.
Madame Wu might have wanted to repeat the experiment to make sure of the result, but she didn’t have a chance. It was customary for some members of the physics department to have lunch at Lucky’s Chinese Restaurant on Fridays and on this friday “TD” Lee mentioned Wu’s preliminary result. Leon Lederman and xxx Garwin, on hearing this, thought they had a chance to do the Pi-Mu-E experiment at Columbia’s Synchrotron. They immediately drove there and elicited the cooperation of graduate student xxx yyy who was scheduled to work on the accellerator that weekend. By monday they had the result that Lee and Yang had predicted and were ready to announce it on the front page of the New York Times. Cooler heads pursuaded them to hold off and make a joint announcement with Madame Wu on Wednesday. It was a world sensation. The American Physical Society was having its major yearly meeting in New York in a short time, and the special session for last minute papers was held in a large ballroom and overflowed into the corridors.
Within a month an experiment was done that proved that parity was not conserved using equipment that could have been found in a good high school, but the calculation that showed it was possible was so complicated it would not have been done if the result had not been expected.
The important result was not that parity wasn’t conserved in interactions involving the weak nuclear force. The important result was that if an experiment is difficult enough, or a calculation is difficult enough, scientists are as likely to believe something convenient but untrue as are any other professionals like theologians. The Law of Conservation of Parity, though completely untrue, reigned as a “Law Of Nature” for a quarter-century.
So just because the current generation of scientists believes something, as long as that something can’t be proven, it is no more to be relied upon than any other religious dogma.
The particular religious belief that gets us into trouble the most is “survival of the fittest”, Spenser’s paradigm. Darwin’s original paradigm, “survival of the just barely fit enough” is accurate, but it requires modern mathematics to get results out of it, so Darwin was conned into accepting Spenser’s as a substitute. But a mistaken paradigm, even if the math is easier, is still a mistake.
I will be approaching this same conclusion from other directions in future blogs.