After graduating from high school, Helmholtz served in the army for 8 years and entered the Royal Academy of Medical Sciences in Berlin at public expense. 1842, after obtaining the doctor's degree in medicine, he was appointed as a Potsdam military doctor. From 65438 to 0847, he gave a lecture on the conservation of force at the German Physical Society, which won great prestige in the scientific community. The following year, he became an associate professor of physiology at the University of Konigsberg. Helmholtz put forward the law of conservation of energy mathematically for the first time in this speech. The main arguments are as follows: ① All sciences can be attributed to mechanics. ② It is emphasized that Newton's mechanics and Lagrange's mechanics are mathematically equivalent, so we can use Laplace's method to measure force by the energy transmitted by force or the work it has done. All these energies are conserved. Helmholtz developed the work of J.R. Meyer and J.P. Joule, discussed various known scientific achievements in mechanics, heat, electricity and chemistry, and rigorously demonstrated the law of conservation of energy in various movements. The content of this speech was later published as a monograph called "Conservation of Force".