Resource: Law of conservation of energy

We have already discussed conservation laws—mass and charge. As you might suspect, there is also a law of conservation of energy.

The genius of Einstein and others caused scientists to rethink this idea, as well as the Law of Conservation of Mass. When scientists are trying to be exact, they state the Law of Conservation of Mass-Energy. The total quantity of mass-energy remains constant, but one can be transformed into the other. So far, humans have discovered how to change matter to energy, but we have not been very successful at transforming energy to mass.