Before Galileo's experiment on the leaning tower of Pisa, Aristotle in ancient Greece thought that the speed of falling objects was different. Its falling speed is proportional to its weight. The heavier the object, the faster it falls.

2. 1953, worked in Brookhaven National Laboratory for one year, and published the paper Isospin Conservation and Isospin gauge invariance in cooperation with Mills, in which the later famous Young-Mills gauge field equation was put forward.

However, at that time, Li Zhengdao had serious doubts about whether the starting point of this paper was correct. Once, when he came to Columbia to give the right way, Li told Yang his opinion. After a heated discussion, Yang agreed with Li and signed his name on * * *. After Li Qianyang, he published a paper "Conservation of Heavy Particles and Transformation of Universal Norms".

This incident enabled them to cooperate again, which was also a romantic and magical period in their physics career.

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The above information is for reference only, and I hope it will help you to study the problem.

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