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
> i know it’s the ability to do work and all that, but this isn’t what energy is, it’s what energy does.
That’s not true. The ability to do something isn’t the action itself.
When a system has energy, that energy can be used to do lots of things; pushing something, shining a light, heating something up. But before the energy is converted, it isn’t any of those things; it’s the property of the system that allows it to do those things.
So the way understand it, it is simply a property of matter that we have discovered. Other measurements like length, mass, volume, etc., make intuitive sense to us because we can directly observe them. We can measure the length of the object by stacking several smaller objects with the same length for example (where these smaller objects function as the units). But measuring energy is not so obvious, and it took numerous experiments to figure out that a value like that “exists”, namely that it makes sense to use it
The energy held in something is its mass times the speed of light squared
That energy may be expressed in a myriad of ways.
We don’t know what energy is but u/zefciu perfectly described what we can tell: It stays the same and we can use it.
Energy cannot be created or destroyed…..only changed.
That’s all I know, thanks for coming to my Ted talk.
I dont like these answers so I will offer my own, which is more philosophical but still accurate.
Energy is potential to change a system. All energy can be thought about as potential energy. What energy *is* is a measure of how much change can be imparted from within a system to outside that system.
At its most fundamental level, energy is the potential to actuate change.
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.
It’s like money, but a value store of work. You can save it (potential energy) you can use it (kinetic), you can borrow but can’t really go negative in the absolute sense. It’s fake like money as a construct but at the same time feels real through everyday experiences.
I’ve often wondered what energy is as well. On a fundamental level. I never took advanced classes in HS and college was out of reach so I’m really clueless.
But I think about energy coming from the sun, and being absorbed by a plant, which uses that energy to grow bigger. Then we cut that plant and consume it and the energy stored in it is transferred to us. Then that energy is used to do work like walking or lifting an object. But then where does the energy go from there? If I slide a cup across my table, I put some of that energy into overcoming the friction of the cup and the table, but where does the energy go from there? Is it lost?
All of this thought process could be completely wrong. I have no clue. It’s just what I think about during a 12 hour shift doing meaningless manual labor.
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