E
E is Energy.
Energy is not a glowy substance that shoots through space.
Energy is not the "stuff" that comes out of Buck Roger's laser gun.
Energy is not "tells ya how much of the city you can flatten."
Light, or photons are not "pure energy".
Energy is not a substance, at all.
In 1918, Austrian mathematician Emmy Noether proved the following theorem: If a physical system contains a continuous symmetry, then there must exist a corresponding single quantity which will be `invariant` under the translations of that symmetry. The single quantity will be "conserved", and the definition of that quantity will constitute a "conservation law".
For a physical systems which contain time-symmetry, the corresponding invariant quantity will be denoted by the letter E. We will call this E by the name "Energy".
What is Energy? It is an invariant quantity of physical systems which obey time-symmetry.
Fact-check me, Philosophy Now forum....
.... I dare ya.
