Does energy exist?

On the real world, or is it just a theoretical concept created by humans to facilitate on understanding and calculations?

I was discussing this the other day, and it seemed that we couldn’t say an object had energy, but were in some states that we call energized. For instance a moving object doesn’t have something on it that we can call energy, the only thing it has is movement. So we introduced the concept that Ec = (1/2)m * v^2, but in fact the energy it has is nothing more than a theoretical concept used to express the idea.

When water is getting heat by a flame, we could say there’s an energy transference between the gas (hotter) and the water (colder). In fact there’s nothing going anywhere, what’s happening is particles with different speeds shocking (gas particles shocking with the particles of the metal of the pot which in turn shock with the water’s). Nothing, besides the theoretical energy concept, is being transferred.

What do you think about this?

I went to wikipedia to find the simplest definition of energy for you, and wikipedia defined energy as a scalar physical property. Wikipedia gives other examples of scalrs, such as, mass, charge, or temperature. I suppose energy is as real as those things, which likewise, we conly describe in relation to something else. One can futher say, if all those things aren’t “real”, then no one has anything to talk about, ever. But by that time, we’ll be in great debates territory.

Energy’s at least as real as mass, as the two are equivalent (remember, E = mc[sup]2[/sup] and all that). As a concrete example, an atomic nucleus composed of a number of neutrons and protons has less mass than all its constituent parts taken together, due to the binding energy (taken to be negative) between them. If energy wasn’t ‘real’, how else would you explain this mass defect?

Some old physics textbooks used to define energy as the capacity to do work. This definition is now regarded as out of date, but I think it at least serves the purpose of getting you thinking along the right lines. ‘Energy’ isn’t material ‘stuff’; it’s a concept that enables us to model and measure some differences between discrete systems and some causal relationships between them (if you heat this up, the reaction occurs more quickly). It also gives us a way to understand what remains constant within a closed system (the sum total of the energy) and what doesn’t have to (where it is stored, how evenly it is distributed, and how we might usefully manipulate those factors to our advantage).

Whether energy ‘exists’ is a philosophical question centred around the defintition of ‘exist’. But I’d say that the OP has confined themselves to examining purely mechanical, classical, non-relatistic systems and I’d ask them to look at how well their arguments hold up on systems that don’t have these 3 properties.

Isn’t this just a variation on the question you asked in Great Debates last week?

I’ve often wondered about force.

“You apply a force to accelerate an object.”

IMO, this is not a definition of force; it is simply stating the *result *of a force.

So what is a force?

Grade 6 physics:
Energy is the ability to work.
An object may have (typically has both) potential and kinetic energy.
Heat and motion are good examples of kinetic energy.
Position in a gravity well or chemical bonds are examples of potential energy.
-As water or a falling object get closer to the center of the earth (a gravity source), they turn potential energy into kinetic energy. We may use that water movement to turn a generator, creating elctrical energy.
Electrical energy is a potential (voltage difference) until a conductive path is closed, in which case that potential causes electrons to move (kinetic) reducing the potential energy.
-when gunpowder explodes, turning chemical bonds into heat and motion, potential energy becomes kinetic.
-when a rising object is slowed by gravity, it turns kinetic into potential enery - until it reaches top of its arc, stops, and starts to fall faster and faster…
-When two smaller atoms (nuclei) fuse, or a very large one splits, energy is release as high-speed subatomic particles and energetic photons of various wavelengths.

Energy is a real concept that can be quantified in many forms. It can transform from one form to another (according to the 3 laws of thermodynamics). I.e. chemical to electric, electric to heat, heat to electricty or molecular bonds or motion, etc.

Let me clarify a bit, i know what energy is, and that it exists at least in our brains. What i’m trying to ask is that if energy is just a concept created by humans to simplify how we deal with the universe. For instance, i know in thermodynamics i studied some concepts that don’t really exist in systems, but that we created to simplify our job in solving problems or explaining situations. System X has [concept] of a value of [units]. In reality the system doesn’t have that concept in itself, we just created it so we can use it on other equations etc.

What criteria should we use to distinguish between physical quantities which “really exist” and those which are just mathematical creations useful in describing physical behavior?

It’s an energy field created by all living things. It surrounds us and penetrates us. It binds the galaxy together.

Does the computer you’re sitting in front of exist? Do you exist? Does anything exist?

Assuming that the answer to that is “yes”, then you can just as well say that energy exists, entropy exists, enthalpy exists, Gibbs free energy exists, and so on.

Energy is basically a measurement. It exists in the same sense that, say, length exists. That is, a very confusing and philosophical sense. It does not exist in the same sense that, say, a rock exists. (Other than the rock has energy)

Really, energy is the measurement of the difference between states. (A state is basically just all of the measurables of a thing) For example, potential energy. The potential energy of a rock at a certain height isn’t a terribly meaningful thing, or even a well defined thing. However a rock that CHANGES height changes potential energy in a very meaningful and well defined way.

Or take kinetic energy. It seems like that’s a measurement of a single thing, velocity. But if you imagine a universe that only contains a single rock, you can’t say what its velocity is or even that is HAS a velocity. Depending on what your frame of reference is, you’ll get a different kinetic energy. But if you accelerate that rock, then the velocity will change in a meaningful and well defined way, and you can say useful things about change in kinetic energy.

Anyway, what I’m trying to get at is that energy isn’t some distinct thing that matter is full of, no matter how often bad SF yammers on about “life energy” or similar nonsense. Stuff exists in various states, and the way it changes states is described and measured as energy.

Of course it exists, just not in the real world. You can’t point and say “Look, here’s a bit of energy.” in the same way as you can point to a rock, or an atom, or anything that we can observe, because it’s not there. The only place i’m arguing it exists is on human’s mind as a concept.

Duct tape? :smiley:

But ARE rocks and atoms “there”? Is there REALLY such a thing as “a rock”, or is “a rock” just a convenient way of referring to a collection of observations and predictions about how a localized chunk of the universe behaves?

Energy is *exactly *as real as atoms and rocks. It’s a convenient way of referring to a collection of observations and predictions about the behavior of the universe.

Sure I can. Why wouldn’t I be able to? Did ferrets gnaw off my index fingers or something?

Is it? You can say what a rock is, but can you say what energy is? Not how it works, or how it transferes and its diferent forms, but what it is like you can say for a rock that it is a bunch of atoms put together (simply put).

But all you’ve done is define a rock in terms of something else. You haven’t said what it IS. And then the question becomes what is an atom? Or what is a proton? Or what is a quark? Or what is matter? Eventually in trying to say what a rock IS, we get down to ideas that are just as fundamental as energy. And at that point, really all we can do is describe how something behaves: matter has mass, it creates a gravitational force, etc. None of that tells us what matter IS, just what it DOES.

“Rock” is actually much more of an abstraction than “energy” is. “Energy” describes something very fundamental about how the universe operates, while “rock” is a fuzzy, uncertain idea that can only be understood in relation to other more basic ideas.

You’re saying that we are limited by our senses. And not just by our senses, but by the limited vocabulary we have to describe what our senses tell us in our brains.

But since all that is mere electrical impulses in our brains, then anything else that results from those same electrical impulses, like thoughts and concepts and notions, are exactly as real.

The entire history of philosophy pretty much gets down to where you stand on this one question, and no two philosophers agree on every detail.

However, modern physics is dependent on the understanding that energy is real and can be expressed extremely precisely through a series of laws and equations. Moreover, energy is equivalent both to mass and to information, so they are equally fundamental. A bunch of atoms is a bunch of energy. There is no possible way of understanding them that makes a distinction.

Physics is an alternate but equally valid way of looking at reality. It has its own philosophical underpinnings, which is a field to itself, but working physicists can afford to ignore that.

If all you want to do is keep asking “why” then we have no answers at the deepest levels. For all other purposes the answer to "is energy different from a rock?’ is “no.”