“All the life of the universe may be regarded as manifestations of energy masquerading in various forms, and all the changes in the universe as energy running about from one of these forms to the other, but always without altering the total amount.”
— Sir James Jeans, The Universe Around Us, 1929
We all know what energy is. When we have it, we can do things; when we don’t, we can’t. The same applies to trains, cars, planes, cookers, sewing machines, TVs, guitars, lamps, drills, pencils, tap water – in fact everything.
Yet the concept of energy is a bit nebulous. It’s tricky answering the question, “What is energy?” except with, “Well, it’s energy, you know... it’s what we need to do things.” It’s a mystical invisible thing that can…