From 1842 to 1847, the law of conservation of energy was discovered. First, in 1842, Meyer discovered the law of conservation of energy and measured the mechanical equivalent of heat. Subsequently, Joule and Helmholtz independently discovered the law of conservation of energy at 1843 and 1847 respectively. Helmholtz also studied the thermal phenomenon of muscle movements through experiments and published a paper "On Material Consumption in Muscle Movements". Through this series of theoretical and experimental preparations, he delivered a speech entitled "On the Conservation of Force" at the Physical Society of Berlin on July 23rd, 1847. He not only expressed the law of conservation of energy experimentally but also theoretically, and gave a convincing proof. Helmholtz expanded the application scope of the law of conservation of energy, making it not only limited to mechanical energy and thermal energy; In addition, he also pointed out the universality of this law: all processes including force, heat, electricity and physiology obey the law of conservation of energy.
Since Helmholtz University studied in medical school, many research achievements in his life were the products of the combination of physics and physiology. He initiated the field of music physics, and published many papers in this field, such as On the Combined Tone (1856), On the Physical Causes of Harmony Interval and Disharmony Interval (1858), On the Vowel Sound Quality (1859) and On the Open Tube Vibration.
Li Zhengdao once commented on Helmholtz: physics and music, sound waves and scientific symphonies. Helmholtz truly combined art and science, music and physics with the thoughts of scientists and artists closely and organically.