Sixty-eight years ago today, on February 22, 1957 (January 23, 1957), Chinese-American scientists Li Zhengdao and Yang Zhenning proposed the law of parity non-conservation. Parity conservation means that under any circumstances, the mirror image of any particle has exactly the same properties as the particle except for the spin direction. The law was proposed in 1926 and proved successively in the strong force, electromagnetic force and universal gravitation, but in 1956 it was confirmed that it did not hold in the weak interaction. This conclusion was proposed by Chinese-American scientists Yang Zhenning and Li Zhengdao, and won the Nobel Prize for it. On February 22, 1956, Yang Zhenning (right) and Li Zhengdao (left) jointly published an article that overturned one of the central messages of physics - the conservation of parity? The behavior of elementary particles and their mirror images is exactly the same. The law of parity non-conservation refers to the asymmetry of the motion of matter that are mirror images of each other in weak interactions. It was verified by Wu Jianxiong in 1956 with cobalt 60. Yang Zhenning and Li Zhengdao won the Nobel Prize in 1957. Yang Zhenning, born in Hefei, Anhui Province on October 1, 1922, graduated from Southwest United University in 1942 and entered the research institute of Tsinghua University. Two years later, he received a master's degree and was admitted to the United States at a public expense. He went to the United States in 1945 to enter the University of Chicago and received a doctorate in 1948. In 1949, as a postdoctoral fellow at the Institute for Advanced Study in Princeton, Yang began his research in particle physics with Tseng-Dao Li, whose contributions to physics included particle physics, statistical mechanics, and condensed matter physics. In addition to discovering parity non-conservation with Li Zhengdao, Yang Zhenning also pioneered the "Yang-Mills gauge field" with R. L. Mills and the "Yang-Bacchus equation" with R. Baxter. The American physicist and Nobel laureate E. Segre praised Yang Zhenning as "one of three theoretical physicists in the world who can be regarded as all-rounders for decades." Li Zhengdao was born in Shanghai on November 25, 1926. A Chinese-American physicist, he studied at the University of Chicago Graduate School in 1946. Three years later, he passed his doctoral dissertation with "special insights and achievements". He was known as "Doctor Prodigy" at the age of 23 and was promoted to professor at Columbia University at the age of 30 in 1956. When he met with Chairperson Mao Zedong on May 30, 1974, he suggested opening a youth class at the University of Science and Technology of China, and his suggestion was adopted.