# Law of Conservation of Energy

This law governs all natural phenomena that are known to date. There is no known exception to this law.

It states that there is a certain quantity, which we call energy, that does not change in the manifold changes which nature undergoes.

*Idea from Richard Feynman:*

That is a most abstract idea, because it is a mathematical principle; it says that there is a numerical quantity which does not change when something happens. It is not a description of a mechanism, or anything concrete; it is just a strange fact that we can calculate some number and when we finish watching nature go through her tricks and calculate the number again, it is the same.