Like, i know it’s the ability to do work and all that, but this isn’t what energy is, it’s what energy does. What IS energy tho?
In: Physics
It’s not really anything. It’s kind of like asking what a dollar is. You can think of it as a piece of paper with a picture of George Washington on the from and an eagle and a pyramid on the back, but then what happens if you exchange ten of those for a picture of Alexander Hamilton and the U.S. Treasury Building on the back? It’s, like, a tenth of one of those pieces of paper, but in some abstract way; you can’t just cut off the part that’s a dollar. Originally there was some silver or gold in a vault somewhere, and the paper was acting like a claim check, but now it’s a claim check for nothing in particular, except the abstract notion of a dollar. And then you have things like bank accounts and debts — you can have *negative* dollars somehow! — so it’s just entirely abstract. It’s just a kind of accounting trick.
And that’s more or less what energy is: a kind of accounting trick to help sort out what’s happening in some physics problem.
It’s not like it’s even some intrinsic property of a thing. Think about this: a one kilogram ball thrown at ten meters per second as 50 Joules of kinetic energy (m v^2 / 2), but in another frame of reference, maybe the ball is traveling at 20 m/s, so it has 200 Joules of kinetic energy, and in another it’s at rest, and has zero Joules of kinetic energy. Similarly, potential energy depends on what you might fall towards — the ground? the center of the earth? the sun? the black hole at the center of the Milky Way? Or are we just talking about negative potential energy with respect to some point far away in intergalactic space?
You can’t look at some object and say, “this is how much energy this has”. So really all it is, fundamentally, is a thing you can use to do some kind of accounting to help solve physics problems.
That’s true of most things in physics.
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