Energy is quite an abstract concept. One cannot point to an object and say 'here is the energy of the object'. One cannot see or hear energy. Still, energy is everywhere. The poet William Blake has written:
"Energy is the only life, and is from the Body; and Reason is the bound or outward circumference of Energy;"
"Energy is Eternal Delight."
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William Blake (1792 - 1882)
It is difficult to give a definition of the term 'energy' the way physicists use it. Let us start by listing some of the properties of energy. This is done on the next page.
Can you think of some properties of energy yourself? How would you explain to somebody what energy is?