This idea is called the first law of thermodynamics, and sometimes it can be simply summarized as: "Nothing can't be born", or in other words, you can't be much less. That is to say:
Helmholtz is one of the founders of the principle of conservation of energy, and he is also famous for his contributions to ophthalmology, anatomy and physiology.
As seen by Blake and Watt, a heat engine (Watt's steam engine is the first successful example) can convert thermal energy stored in gas into kinetic energy in turbines and pistons. That is to say, because the gas expands after being heated, the thermal energy stored in the steam can be converted into motion. The original energy in the system is the chemical potential energy in fuel wood or coal, which is used to generate steam.
In the history of physical science, the first law of thermodynamics is one of the most revolutionary ideas. As the scientific historian Alistair Cameron Crombie (1915-1996) said, "its significance and the questions it raised dominated the physics from Faraday and Maxwell's electromagnetic research to Planck's introduction of quantum theory in 1900." With the appearance of Einstein's physics in the 20th century, it will be proved that the concepts of energy and matter need to be considered together. Obviously, energy can sometimes be converted into matter and matter can also be converted into energy.
As Maxwell wrote in his eulogy to Helmholtz:
"To evaluate the scientific value of Helmholtz's paper" On the Conservation of Force ",we must ask the discoverers of the greatest discoveries in thermodynamics and other fields of modern physics how many times they have read this paper, and how many times in their research career, they feel that Helmholtz's weighty narrative acts on their hearts, just like an unstoppable driving force."
In his later years, Helmholtz became the mentor of Max Planck (1858- 1947), the founder of quantum theory. Through Planck, Helmholtz's influence will be further expanded in the 20th century.