Hum… let’s temporarly put the energy of the mass aside, and for instance discuss about the kinetic energy. Let’s say a car is moving, so for us, we say it has kinetic energy equal to (1/2)mv^2. If an alien species came with another set of equations and laws that work as well on our universe to understand the world, it would be impossible to argue aggainst the fact the car is moving, but they probably could use other equations that don’t include the concept of “energy” to work with the universe. They would have never observed such phenomon called energy, since they would use other concepts to explain similar phenomena. Thus, movement being real, and “energy” human made. Does that make sense and seem possible?
Nope. You’re simply handwaving. Whether it is possible to understand the universe without the concept of energy is the question you’re asking. You just redefined the discussion by making one answer part of your axioms. This is the literal meaning of begging the question. It can’t work.
Like everything in physics, what a term means depends on what theory you’re using. A “force” in Newtonian mechanics is something that causes mass to accelerate. It doesn’t say anything about what fundamentally a force is, only what it does, but what a force is will depend on what’s doing the forcing, so the theory itself is very general. In Lagrangian mechanics, there’s no such thing as forces, everything happens due to the minimization of the action. It’s not that the physics is different (it’s still describing the same universe), it’s just a different way of looking at things.
I suppose it’s plausible that aliens wouldn’t decide to give a name to the combination of 1/2 times mass times velocity squared, but that’s just semantics. We didn’t just arbitrarily throw those quantities together and call it “energy” because we felt like it, we call such a quantity its own unique name for the sake of convenience, but also because it represents something that’s useful in explaining experimental results.
Let’s look at something simpler, momentum. Momentum is simply mass times velocity. We can say something has mass, so mass exists, right? You seem convinced that velocity exists, so we have that. Does mass times velocity exist? If two billiard balls hit each other and we measure their velocities afterward, the velocities turn out to be dependent on both their individual masses and their initial velocities before they hit. So we group the terms together in something called “momentum”. We could say that “the product of the mass and velocity is conserved” but for the sake of convenience we shorthand “the product of the mass and velocity” as “momentum”. Is momentum then a human construct? The word itself is, but the concept is very real. Energy works the same way.
Thanks for pointing that out, i hadn’t noticed.
I think i will grab the other paralel discussion because it seems to be going in the same direction.
So if we can view the universe without the concept of force but using another(s) concept(s), and everything still makes sense, forces - like perhaps energy - could be imaginary ways to explain the same phenomena as in Langrangian mechanics.
Another example. Centers of triangles: Centroid, orthocenter and circumcenter. They’re imaginary. They’re constructions of the human mind. Yes they exist, but only because we created them. An uneducated person wouldn’t be able to know where they are, yet he would distinguish a tringle from other shapes, from the number of sides. Triangles exist independently from the observer, centers of tringles don’t, and i argue energy to be the same.
Physics and science is just a model, it doesn’t describe what something “is”. You could come up with a model of physics that doesn’t use the concept of energy (and therefore make energy not “exist”) but thus far to my knowledge no one has, because looking at the universe that way doesn’t reveal anything useful.
I’m not sure what you’re getting at with the triangles thing. Terms like “orthocenter” exist just as much as a “triangle” does. A “triangle” is a name for a geometric shape with three sides. A “triangle” only exists in that we have created a name for an object with three sides. Objects with three sides do exist, just like the centers of them exist.
Are you trying to say that something doesn’t exist until we come up with a definition for it? That triangles didn’t have any center until someone decided to come up with a name for it? Otherwise I’m not really sure what your point is.
That’s nice. Now what?
I mean this literally. You have just made an enormous claim about the foundations of all our understanding of science and reality. If you make a claim of this magnitude, it must have some consequences. What are they? And how do you justify them?
It’s not clear how real movement is. For example, if the holographic principle is correct then our normal conception of the universe consisting of a 3-D space with objects moving through it is merely an anthrocentric illusion.
It worth keeping in mind that many things that seem intuitively obvious about reality may in fact only be convenient computational fictions that helped us to survive as hunter/gatherers on the Africa plain. Much of the history of physics has been a gradual undermining of our intuitive strategies for understanding the universe. Even things that seem as fundamental as space, time, and movement may in fact only be human constructs.
It’s Sunday afternoon at 4:30pm and I’ve been trying to get my sorry butt to the gym since 8am. So in answer to your question, no energy doesn’t exist. At least not today 
I don’t think the distinction between “real” and not “real”, in the manner of this thread, is well defined. But even more to the point, I don’t think it has any use. I think it’s a chimera. What would dissuade me from this point of view?
Is movement real in basic quantum mechanics? Sure particles has a dynamcialobservable for postion and even one for velocity should you so wish, but like any dynamcial osbervable these are not always have exact values.
You’re asking for evidence that the distinction between “real” and “not real” is real?
The issues raised in the OP continue to puzzle me. Since my grasp of physics is lacking, I’m not clear on what this “Energy” thing is. I could use an example. Wikipedia maintains that delE = W + Q + E. But since I don’t have a grasp of the units of any of those parameters, this decomposition means little to me. Does anybody have a link that they would be willing to defend? Simpler examples are of course preferred.
Posters have claimed in this thread that energy is observable, as observable as a rock. I believe you, but I’m taking that on faith: I have not seen it demonstrated.
This is highly contentious. Mathematicians seem to believe that mathematical principles are discovered, not created. We’ve discussed this issue on the board before; I have not resolved it to my satisfaction.
Energy is mass and mass is energy. Here is a computation I did many decades ago that astonished me, although in retrospect, it shouldn’t have. A body moving with respect to my reference frame gains weight. A body of mass m moving at speed v has a mass of msqrt{1/(1 - v^2/c^2)}. After carrying out some standard manipulations and very good approximations when v is much less than c, you discover that the increase in mass is equivalent to an energy of almost precisely mv^/2. In other words, what we call kinetic energy is just the relativistic increase in mass. I guess every physics student carries out this calculation, but the only physics I ever took was classical mechanics…
Concepts that would have to be equivalent if they were able to, for instance, predict how much the car dents the wall if it crashed into it; and if the concepts are equivalent in this way, then that’s really just giving energy a different name, isn’t it?
If you can point, there is energy.
That simple action proves the existence of energy by demonstrating the shifting of mass to a different location in space (time, also).
So in fact, anytime anyone points at anything (or nothing at all) and says “Look, here’s a bit of energy.” They are literally* making it so, and also giving a hands-on lesson to any doubters in the vicinity.
*Folks here (including me) tend to give all kinds of crap to people who use the word “literally” improperly. I deliberately employed it here because I find it a perfect occasion to do so.
I think I understand you now, and I think that you are wrong.
I think that you are bumping up against the reality of language. Does reality create the language, does language create the reality, does anything exist beyond our ability to put it into language … obviously, the answers are ‘yes’.
Mathematics are highly specialized forms of language.
The concept of energy was created to described observed phenomena, as said elsewhere. The continuing refinement of the definition has refined the concept and affected the observations of phenomena.
Definitions limit and exclude - this is a plant, not an animal; this is a fruit, not a leaf; this is an apple, not an orange.
Can the limits be drawn elsewhere? Obviously - iron, blood, and apples are all red.
Can the limits be drawn in completely different ways? With words, definitely; languages have words that do not exist in other languages, ‘pink’ for example. “Tia” is an interestingly examples. These are relatively trivial example, admittedly.
Can the limits be drawn in ways we cannot imagine yet with numbers?
I assume they can …
I would be inclined to look to the conservation laws to think about energy.
In classical physics we have conservation laws like conservation of momentum, mass, angular momentum, charge, and energy. Quantum physics added a heap more. Relativity took at least one away. Mass.
But the only thing relativity did was combine mass conservation into a larger energy conservation law.
Energy is conserved. You can convert energy from one form to another. Kinetic energy can be converted into electromagnetic energy. The binding energy in an atomic nucleus can be converted into electromagnetic and kinetic. The mass equivalent of the energy has gravitational mass. (A wound clock spring is heavier than an unwound one by exactly the mass equivalent of the energy it stores.) The binding energy holding quarks together accounts for most of the mass you and I and the rest of the observable universe are made of. And it is all the same thing. It is difficult to say that this thing is less real than any other phenomenon. Indeed there is probably a case for saying that, if anything, it is the most real of them all. Energy acting over time is what makes the universe change state, and thus things happen. The fact that it is subject to reasonably simple laws, like conservation, and thus amenable to mathematical description, doesn’t make it less real. Again, I might argue that it makes it more real.
I agree J66, i think i’m starting to see a part of the mistake, but i’m still having some troubles swallowing this. Going back to the triangle’s example, the center of a tringle, as well as any point inside it, exist, whether i have a name for it or not.
But let me bring the example i gave at the start. Calorific energy. We say there’s energy transference from a hoter system to a colder. We know, though, that what happens is particles shocking with each others. There’s no “fluid” or anything material really going from one place to the other, so there’s no transference of anything that is material - at least that we know of.
So if it’s not material, what else can it be? An abstraction perhaps.
Another example. Let’s say i call the net of people going in and out of a bar, heat. So if we have more people going out than in, we say the heat is decreasing, and vice versa.
Now, can we say that “heat” - in this context - exists? There’s not really such thing as heat - with the meaning mentioned above - decreasing/increasing in the real, material world, except in our brains, since we created that concept. Why can’t it be the same with energy?
If you touch a red hot iron bar it will damage your flesh. That is a pretty real effect. The heat in the bar is the mixture of kinetic and potential energy of the atoms vibrating in the bar. They transfer kinetic energy to your flesh. The extra energy in your flesh is enough to break chemical bonds. Energy may be converted from kinetic form to electrostatic in the creation of new bonds as well. Your hand gains energy in the form of heat - again transferred as kinetic energy. And energy is conserved. It was neither created nor destroyed in the process. You even weigh slightly more due to the net gain in energy in your hand.
It seems the crux of the question is whether anything that is not “material” is real. At which point you might need to define “material”. Given that most of your mass is binding energy, simply having mass does not material make. Charge is a conserved quantity, but it isn’t clear that it is material either - you can’t get a naked charge that is not in some way bound into other conserved properties - like mass and spin.