The article of autumn water is not stained with dust! Commemorating the 120th anniversary of the birth of Dirac, the pioneer of quantum mechanics
On August 8, 2022, the 120th anniversary of the birth of Paul Dirac, the pioneer of quantum mechanics, was awarded the Nobel Prize in Physics in 1933 for "the discovery of new forms useful in atomic theory" (i.e., the Schrödinger and Dirac equations, the fundamental equations of quantum mechanics). Dirac and Erwin Schrödinger were jointly awarded the Nobel Prize in Physics.
In his famous lecture "Beauty and Physics", the famous physicist Yang Zhenning, who is also a Nobel Prize winner in physics, gave Dirac high praise and described him as "an essay in autumn water that does not stain the dust". The following is an excerpt from "Beauty and Physics".
Dirac 1969 in Stony Brook, New York, USA (Photo by L. Eisenbud)
This story is extremely popular because it does describe one of Dirac's characteristics: not many words, and the simple, direct, raw logic contained within them. Once he captured his unique logic, which no one else would have thought of, his essay reads smoothly, like "an essay in autumn water without dust", without any dross, straight to the depths, straight to the mysteries of the universe.
Dirac's most remarkable work is the two short articles published in 1928, in which he wrote down the Dirac equation
(pcα+mc2β)ψ=Eψ
where p is momentum, c is the speed of light, m is the mass of the electron, E is energy, and Ψ is the wave function, all of which were already familiar ideas at the time. α and β were new ideas introduced by Dirac, very simple but extremely influential, and played a superb role in both physics and mathematics.
The Dirac equation on Dirac's tombstone
This simple equation was an astounding achievement, an epoch-making milestone: it gave a new dimension and a new and extremely accurate understanding of both atomic and molecular structure. Without this equation, atomic and molecular physics and chemistry would not exist today. The magnetic resonance imaging (MRI) technology used in hospitals today would not be possible without the ideas introduced by Dirac, but this technology is really only a very small application of Dirac's equations.
Dirac's equation "creates something out of nothing," and "breaks the ice" by showing why electrons have "spin" and why "spin angular momentum" is 1/2 rather than an integer. Anyone who first understood this mystery could not help but marvel at it as a "stroke of genius", a brilliant calculation that no one else could think of. W. Heisenberg (1901-1976), the most famous man of his time, read Dirac's article and, unable to understand how Dirac could have come up with this miracle, wrote a letter to W. Pauli (1900-1958) on May 3, 1928, describing his troubles.
In order not to be continually annoyed by Dirac, I have done a different subject and got some results. (Note: This result is another important contribution: why magnets are magnets)
Dirac
Although the beauty of Dirac's equation was immediately recognized by his peers at that time, it had an unprecedented property called "negative energy", which was absolutely unacceptable to everyone. In 1931, Dirac boldly proposed the theory of antiparticles to explain the negative energy phenomenon. This theory was not accepted by his peers, and many stories of half envy and half ridicule were circulated. It was not until the discovery of the antiparticle of the electron by C.D. Anderson (1905-1991) in the autumn of 1932 that the theory of antiparticles was gradually recognized as another milestone in physics.
Among the physicists of the twentieth century, Dirac was the one with the most unique style. I wanted to write down his style for my friends in literature, history, and art, but I never knew how to write. Last year, I happened to read an article in the "Great Park" section of the Hong Kong Ta Kung Pao, which quoted a poem by Gao Shi (700-765) in his "Reply to Hou Shaofu": "The spirit of nature is out of ten thousand images, and the bones are beyond the ordinary." I was very happy to see that these two lines could not be better used to describe the Dirac equation and the theory of inverse particles: on the one hand, the Dirac equation is indeed all-encompassing, and the use of the word "out" to describe Dirac's inspiration is particularly evocative. On the other hand, he defied the cynicism of N. Bohr (1885-1962), Heisenberg, and Pauli and other great physicists of the time in the four years after 1928, and always insisted on his theory, and finally won all the victories, which is just like "the spirit is more than normal".
But what is "spirituality"? The dictionary explanation of these two words together is not pertinent. "inspiration", "spirituality", "spirit" (ghost), etc. seem to be added up to mean direct, original, unrefined thought, which happens to be the spirit of Dirac's equation. It was just at this time that I spoke with Dr. Tong Yuan-fang of the Chinese University of Hong Kong about an article by Qian Lockqiao in the June 1996 issue of Twenty-first Century, and learned about the spiritualism of Yuan Hongdao (1568-1610) [and later Zhou Zuoren (1885-1967), Lin Yutang (1895-1976), etc.]. Yuan Hongdao said that his brother Yuan Zhongdao's (1570-1623) poems were "unique in expressing the nature of the spirit and not in a formal way", which is also the characteristic of Dirac's style. This is also a characteristic of Dirac's style. "He refuses to write unless it flows from his own heart", which describes Dirac's originality!
