Energy

There is a fact, or if you wish, a law, governing all natural phenomena that are known to date.

 

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

 

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.

 

"'어떤 것'이 형태만 변화할 뿐, 사라지거나 더 생겨나지 않는다. 그 '어떤 것'을 에너지라 하면, 에너지는 보존된다."