But what really is energy? The dictionary says it’s “the property of matter and radiation that is manifest as a capacity to perform work.” And it says “work” is “the exertion of force overcoming resistance or producing molecular change.” Putting that together, we get energy being “the property of matter and radiation that is manifest as a capacity to perform the exertion of force overcoming resistance or producing molecular change.”
That was pretty unfun, so for our purposes, let’s call energy “the thing that lets something do stuff.”
But the tricky thing about energy is the law of conservation of energy, which says that energy can’t be created or destroyed, only transferred or transformed from one form to another. And since every living thing needs energy in order to do stuff—and you can’t make your own energy—we’re all awkwardly left with no choice but to steal the energy we need from someone else.
Almost all of the energy used by the Earth’s living things got to us in the first place from the sun.The sun’s energy is what makes the wind blow and the rain fall and it’s what powers the Earth’s living things—the biosphere.
The joule is a common unit of energy—defined as the amount of energy it takes to apply a force of one newton through a distance of one meter. While the sun’s joules can provide any animal with heat and light, the joules that power all of us from the inside enter the biosphere in the first place when the sun gives them to plants.
That’s how food is invented—plants know how to take the sun’s joules and turn them into food.
At that point, all hell breaks loose as everyone starts murdering everyone else so they can steal their joules.
We use “the food chain” as a cute euphemism for this murder/theft cycle, and we use the word “eating” to refer to “stealing someone else’s joules and also murdering them too.” A “predator” is a dick who always seems to want your joules over everyone else’s, and “prey” is just some sniveling nerd you particularly like to bully and steal lunch money from. Plants are the only innocent ones who actually follow the Golden Rule, but that’s just because they have the privilege of having the sun as their sugar daddy—and humans are the biosphere’s upsetting mafia boss who just takes what he wants from anyone he wants, whenever he wants. It’s not a great system, but it works.
And that all went on normally for a while, but in the last few hundred thousand years, humans started to realize something: while it was enjoyable to put new joules into your body, actually using those joules sucked. It’s much less fun to use a bunch of joules running fast or lifting something heavy than it is to just sit on a log pleasantly and hold onto those joules instead. So humans got clever and started to figure out ways to get joules outside their bodies to do work for them—by doing that, humans could have their joules and eat them too. Sometimes the methods would be dickish:
But joules aren’t only in living things. There are joules floating and swirling and zooming all around us, and by inventing the concept of technology, humans figured out ways to get use out of them. They made windmills that could steal some of the wind’s joules as it went by and convert them into mechanical energy to grind food. They built sailboats that would convert wind joules into kinetic boat energy they could control. Water absorbs the sun’s radiation joules and turns them into gravitational potential energy joules when it evaporates and then kinetic energy joules when it rains and slides down land, and humans saw the opportunity to snatch some of those up by creating water wheels or dams.
But the most exciting joule-stealing technology humans came up with was figuring out how to burn something. With wind or water, you can only capture moving joules as they go by—but when you burn something, you can take an object that has been soaking up joules for years and release them all at once. A joule explosion.
They called this explosion fire, and because the joules that emerged were in the useful-to-humans formats of heat energy and light energy, burning things became a popular activity.