The big Idea of energy

[Dave-Sandra]

What is the big idea of energy?

[Clanad]

E = mc^2...

[mibn2cweus]

The "big idea" of energy, is a phrase designed to point out that everything in the universe is energy in one form to another and that the sum of energy is maintained.
Energy can only be transferred or transformed from one form or another such as matter (substance) or light (radiation).
Matter is composed entirely of energy bound up in a specific form. Radiation is energy liberated to travel freely through space until it encounters and reacts or interacts with other energy and under the right conditions alters the properties of, adds to or becomes new matter.