It’s odd seeing the word “energy” bandied about so freely. It’s a truly abstruse concept.

The word was adopted, or perhaps co-opted, as a way of unifying some really odd things, common factors that showed up where there was nothing obvious in common. For instance, what do gravity and a fire have in common?

Think of an airplane. If you start thinking about airplanes in terms of how they work, it becomes fairly obvious that what keeps an airplane up is the engines. The wings are just a way of applying leverage against the air, so that the engines don’t need the power to lift it directly.

If an airplane loses its engines, it doesn’t just plummet straight down. Instead it glides, loses altitude slowly. Power is still available, and that power is being leveraged by the wings to keep the airplane from just falling. It’s not enough power to keep the airplane up indefinitely, like the power from the engines was, but it’s enough that a clever pilot can find a safe place to land gracefully. Engine power comes from fire, burning fuel. Where does the trickle of power that allows gliding come from?

If the airplane did plummet straight down it would make a hole in the ground when it hit. We know from experience, using a shovel for instance, that making a hole in the ground takes power. So wherever that power came from, it’s the same as what lets the airplane glide — falling and hitting uses that power all at once, where gliding uses a bit at a time. The only thing around that the falling airplane and the gliding one have in common is gravity, the force of its weight pushing it toward the Earth.

There is something about gravity that can be converted to power. Equally, there is something about fuel that can also be converted to power. Either way, the power produced by the conversion keeps the airplane up until the source of whatever-it-is is exhausted. Engineers and scientists needed a word for “something” that isn’t visible or tangible, “something” that lurks in gravity and kerosene and a lot of other things that are very different from one another, but that shows up as power when it’s used.

That common concept is energy. Fuel contains chemical energy, so burning it produces power. Gravity contains potential energy, so releasing it produces power. Atoms contain nuclear energy, so splitting them produces power. Light contains electromagnetic energy, which a clever enough arrangement can convert to useful power. Wind contains energy of momentum, which can be used as power to turn a windmill. The only thing those wildly different things have in common is that they “have energy”, but the energy itself isn’t a “thing”, isn’t anything you can touch or feel or take a picture of. There’s no way to detect it until it’s used, and using energy is power. Power makes things happen. “Energy” is a unifying concept, a mathematical abstraction that’s useful to find out where power comes from.

When we’re told to use less energy, what we’re being told is that we must have less power. Which makes it clearer, doesn’t it? Power makes things happen. If we use less energy, we are less able to make things happen. When people who have power encourage us to have less power, their own will look better by contrast, won’t it?

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