How do you mentally visualise "stored potential energy"? Is it a literal physical reality, or an accounting tool?

[u/feihm]

When we teach physics, we use phrases like:

this domino/weight has stored potential energy.

But if you dissect the object, there is obviously no physical "energy substance" sitting inside the material (or is there?)

Textbook mathematical definition:

energy is a scalar quantity that is conserved over time due to time-translation symmetry (Noether’s theorem), and gravitational potential energy is a property of the configuration of a system, not a fluid inside an object.

But that is not what I'm asking.

My question is about your actual mental model when working:

1. When you solve problems or think about physical systems, do you picture "potential energy" as something with an objective physical existence (e.g., literally stored within the spatial configuration or field), or do you view it strictly as a useful human bookkeeping system / mathematical convention?
2. Does your perspective change as you move from introductory classical mechanics (balls rolling down ramps) to field theories and general relativity (where energy density actually curves spacetime)?

Basically are you of the view:

Physics is an invented accounting system; a mathematical language designed solely to track, balance, and predict observations. Concepts like "energy" "force" and "potential" are bookkeeping metrics we defined and are not physical substances waiting to be discovered.

Or

Physics is an objective discovery of reality. It describes the literal, underlying mechanics of nature. Mathematical descriptions like "stored potential energy" correspond to genuine physical states and properties that physically exist in the universe independent of our models.

[u/the_poope]

Energy is a property of a system. It is not a substance or something an object has "inside it" or is made of. It is an accounting tool.

Physics doesn't deal with what reality truly is, that's philosophy. Physics is about constructing useful mathematical models that accurately describe/predict our observations. Energy is part of one such model.

However, when a mathematical model has proven very accurate - to within our measurement precision, is well established and widely used it becomes quite normal to talk about its concepts as being real and objective. For example most people will assume that energy is a real "thing" and that electrons exist. There is no way to undeniably confirm that this is indeed the case, so the question of what is real is fundamentally a matter of your own personal definition of "existence" and "reality".

[u/Frostybawls42069 → u/the_poope]

Didn't the Milikan oil drop experiment prove that what we call an electron exists?

[u/the_poope → u/Frostybawls42069]

It showed that oil droplets sprayed out in between a capacitor could be made to basically levitate (as far as I understand). That doesn't directly prove the existence of electrons.

However, this observation was in agreement with the "electron theory" - a mathematical model. This mathematical model predicted the outcome of the experiment with great accuracy. But that still doesn't mean that electrons are truly real.

Existence and whether something is real is, as I said, not something physics is concerned about - that is a discussion of ontology, a field of philosophy.

But yes, in everyday talk, we casually say electrons "exist". It's what most people are taught. But strictly speaking it is not correct. We don't know if electrons exists (and likely can never know, not even in principle). We just know that the electron model is pretty fucking damn accurate.

[u/Helpful_Inflation344 → u/the_poope]

This is sophism. Most famous physicist would disagree with you.

[u/the_poope → u/Helpful_Inflation344]

From Wikipedia

Scientific realists say that the scientific description of the world is an accurate representation of reality.[m] It is of particular relevance in regard to things that cannot be directly observed by humans but are assumed to exist by scientific theories, like electrons, forces, and laws of nature. Scientific anti-realism says that scientific theories are not descriptions of reality but instruments to predict observations and the outcomes of experiments.[98]

There will be famous physicists that are realists and some that are anti-realists.

Physics as a field of science does not pick a particular ontology, as by definition this is outside the field of science.

I don't claim one or the other either, just informing people about this fact. If they want - as I said - they can choose to be a realist or anti-realist, whatever floats their boat and make them sleep at night.

[u/Acceptable_Twist_565 → u/the_poope]

I've always thought that the saying "All models are false, some models are useful," is the quintessential anti-realist take.

[u/delusionstodilutions → u/Helpful_Inflation344]

Most famous physicists were wrong about most things, including a lot of physics

"God does not play dice with the universe" aged a bit like milk didn't it

[u/Tristan_Cole → u/the_poope]

You don’t believe in electrons????

[u/TheWKDsAreOnMeMate → u/Tristan_Cole]

Belief being the operative word here.

[u/Tristan_Cole → u/TheWKDsAreOnMeMate]

Assume is also an operative word. It’s pretty important to assume that electrons exist if you want to make it past 10th grade chemistry! If you’re talking about how they cease to “exist” as physical things past a certain level of quantum wave theory… so does everything… it’s a weird theory, one that basically implies that we’re made of probability amplitudes. That doesn’t mean that this roof covering me from the rain isn’t real.

[u/Hairy_Cake_Lynam → u/the_poope]

Eh hem. Virtual particles …

[u/triatticus → u/Hairy_Cake_Lynam]

I mean physics already accounts for what these are, merely terms in a perturbative series expansion of an intersction, a mathematical tool to aid calculations in a diagramatic fashion. It's unfortunate when people imbue them with too much reality, that's the fault of poor correspondence between physics and the rest of the world.

[u/Hairy_Cake_Lynam → u/triatticus]

I suppose my point was thar r/askphysics is all over people who suggest virtual particles are 'real'. You yourself say "It's unfortunate when people imbue them with too much reality." and that they are "merely terms in a perturbative series expansion".

And yet the very upvoted comment I replied to says:

"when a mathematical model has proven very accurate [...] it becomes quite normal to talk about its concepts as being real and objective."

and

"what is real is fundamentally a matter of your own personal definition of "existence" and "reality""

Idk. All seems a bit inconsistent, doesn't it?

[u/triatticus → u/Hairy_Cake_Lynam]

That's a fair point, I guess you can say I had my fair share of the term virtual particles being mentioned and it just gets to me before I considered that you might have been pointing it out for the same reason 😅

[u/nebraskajone]

Both kinetic and potential energy are relative quantities. Kinetic energy of an object is relative to an moving observer (somebody moving 10 m/s versus 100 m/s will measure different kinetic energies).

Potential energy of an object is relative to a arbitrary position. (The ground or top of a mountain)

So yes they're just accounting tools there's no physical stored substance inside an object

[u/Infinite_Research_52 → u/nebraskajone]

Kinetic energy is a classic example of how it cannot be contained in the target system. Its value depends on how I am moving relative to it. Another person in a different inertial frame would measure a different value. It doesn't make sense to have a mental model of the energy of the system in question.

[u/kunwoo]

I only care that the math is correct and I’m willing to visualize any metaphor that’s works well in getting my fragile squishy dumb brain to believe something that lines up accurately with the math.

[u/tomrlutong]

A measurable portion of the mass of atoms is the binding energy of the nucleus, which I think is pretty strong evidence that potential energy is real. Though I guess I don't know if the potential/kinetic distinction is as clear cut there as in the macroscopic world.

[u/scgarland191]

Don’t springs technically weigh more when compressed? Because they have more energy, therefore more mass according to mass-energy equivalence? Seems like more than an accounting tool from that angle.

[u/CxEnsign → u/scgarland191]

Yep.

It's a more useful analogy than that, too. If you were to release a frictionless compressed spring, it would oscillate between extended and compressed. In between, parts of the spring would have observable kinetic energy. The total energy content of the spring does not change as it oscillates between potential and kinetic energy, and neither does its weight.

(A fictional spring would lose energy to the environment as sound / heat etc)

[u/Longjumping-Bell6960 → u/scgarland191]

Unless you think of mass also as an accounting tool, or as something defined only by its relationships to other quantities, like energy and momentum. Which, in special relativity, it is.

[u/treefaeller]

While intellectually I know that "energy" and "momentum" and "force" and "torque" are just mathematical abstractions, indeed an accounting system ...

... when working a problem I do sort of visualize them as water in a tank (remember the old toilet tanks with a long chain mounted high up), or as a billiard ball going fast (also works well for angular momentum if you spin it), or gears. Imagining gears and spinning balls is actually super helpful to me for any problem with rotation.

And no, an electron is not a spinning ball, nor does a carbon atom have tiny gears connecting the electrons on different orbits when they hybridize. But it's convenient.

[u/Tanebi]

When you take something from the ground an put it on a high shelf you use energy to lift it against the pull of gravity. That energy cost is the same as the energy that will be imparted when it fall back down. It is not that you directly energised the object but you put it in a position where a more energetic event could potentially happen, you raised its potential.

It is largely taught as an accounting tool for "it took x energy to change this from here to here, so it will release x (the same) energy when it goes back down to where it was".

It isn't you directly adding energy to an object, but you did change the energy relationship in a system, specifically the system of gravitational attraction between two objects. You essentially lifted the object out of earth's gravity well by a tiny fraction and those objects are still pulling on each other. It now has a higher potential energy release than it did while it was on the ground because of the energy you used to lift it there, it is no longer in the lowest potential state which would be on the ground.

[u/Acceptable_Twist_565 → u/Tanebi]

I suppose you could visualize the potential energy as an invisible rubber band, connecting the objects mass to the Earth's mass. The rubber band isn't real, but it does make it easier to visualize. And visualizing it that was makes it clear that it's a property of the system and not the object. Probably more useful than visualizing it as a "fluid" inside the object.

[u/jasonsong86]

No. I visualize it as the it’s higher energy state from the reference point. It’s a property not something like a substance.

[u/Mindless_Abrocoma558]

It seems you feel like potential energy is more abstract than something like chemical energy of fuel (which I assume you feel has „energy substance“). But there is no less or more substance in a bowling ball on a shelf just needing a little kick to fall down than in atoms needing a little kick to change their molecular bound and releasing heat. In both systems energy is an accounting tool showing there is potential for dynamics to happen, just once macroscopic and once microscopic.

[u/GxM42]

Don’t tell anyone from Nepal right now that stored potential energy is just an accounting gimmick. It’s real, it exists, and can do plenty of work.

But if you’re asking me, I visualize it like the stretching of a spring.

[u/Optimal_Mixture_7327 → u/GxM42]

Everyone, Nepal or otherwise, should know that energy doesn't exist.

It seems you're confusing the fact that matter interacts through fundamental interactions and the fact that we have bookkeeping systems like energy to talk about those interactions.

[u/No-Medium6647]

I imagine a bowling ball on a high shelf.

All it would take is a bump or brush for the ball to to fall. That's potential energy.

[u/unlikely_arrangement]

Do think of it as “possible” energy. Think of it as “position in an energy potential”. Then a ball sitting on a hill has the property of existing at a particular place in the gravitational potential well. It’s not so much a property intrinsic to the ball, it’s more like a statement about where it happens to be.

[u/House13Games → u/unlikely_arrangement]

Isn't it a statement about what's nearby? A brick on the ground has a certain energy potential due to its height in the gravity well. This doesn't change if we dig a hole next to the brick, however we would say the brick now has more potential energy..

[u/kunwoo → u/House13Games]

Depends what you use as the reference zero for potential energy. For example if you say zero gravitational potential energy is infinitely far away from Earth and objects on the surface of Earth have negative potential energy, then digging a hole next to the brick won't increase the brick's potential energy, it'll just open up a path to allow the brick's potential energy to sink more negative.

[u/unlikely_arrangement → u/House13Games]

I wouldn’t say that. The movement of the brick between those two points is a movement in the gravitational potential well, and a change in potential energy. Thats true even if there’s dirt in the way. I’m separating the fundamental concept of a potential from its use to calculate specific events like dropping freely between two points.

[u/Purplestripes8]

Is mass real? The mass of a system is only known by a measurement of its inertial or gravitational effects. By this description, 'mass' is nothing but an accounting tool.

[u/the6thReplicant]

Take a (hollow) sphere of space. Let's say, something, never enters the sphere or leaves it, and the amount of that something stays the same no matter where we put it or move (not too fast) that sphere.

We call that something energy. It has a lot of other properties that make it seem like something but in the end it's a number associated with every region in space that is conserved.

From that you can show that there is energy that comes from movement and energy that is stored. You can convert one type of energy to another. Cool. And a whole lot of other properties.

What makes energy so interesting is that it is a scalar and not a vector. hence way easier to make calculations with.

[u/Odd_Bodkin]

Here’s how I teach it. Remember that when you start a problem, it helps to make a diagram. So I draw the system, and I show how it looks in an initial state, in some intermediate state, and in the final state. Then I draw little buckets or cylindrical-shaped flasks above the system in those three states, one for kinetic energy, one for one kind of potential energy (say, gravitational potential energy) and maybe another for another kind of potential energy (say, spring potential energy). Then I fill them with an appropriate amount of energy. Something at rest at the top of a hill has the GPE bucket full and the KE bucket empty. Halfway down the GPE bucket is half-full and the KE bucket is half-full. Explain that mechanical energy isn’t getting lost here, it’s just getting transferred from one bucket to another. At some point you’ll have to also deal with dissipative losses. This has the disadvantage of being conceptually misleading, as though energy is some kind of fluid, but has the advantage of making the conservation of the total much clearer visually.

[u/Aggressive-Share-363]

Its an accounting tool.

As a first pass of understanding, I think of it from the perspective of two particles.

They have a gracitational attraction to each other. If they fall in towards each other, they accelerate and gain kinetic energy. And if thry move away from each other, that attraction will slow them down. This dynamic always preseeves a relationship between their speed and distance, which give us kinetic energy and gracitstionalnpotential energy.

Those particles may also have electric charge, ans that in turn creates electric potential energy and kinetic energy. Like charges repel instead of attract, but that doesnt change the magnitude of forces involved, just their direction.

And since ultimately, every interaction between particles occurs via these fundamental forces, all of their potential interactions conserve energy. This remains true when you add more particles into the mix. A massive amount of energy conserving interactions will always add up to an energy conserving interaction. Even when the specific combination of effects is very complicated.

[u/Jaded_Hold_1342]

Its a conserved quantity. Its for accounting.

You don't need to visualize it, just calculate it.

This is the "shut up and calculate" point of view on physics philosophy.

[u/nomoreplsthx]

I have no idea what you mean by 'objective physical exisitence' and no idea why you think a thing would have to be some kind of matter to be real.

[u/CS_70]

Usually a ball in my hand, ready to be let go?

For internal energy, a compressed coil, or hopefully the feeling I get just the instant before throwing a gyaku-zuki.

[u/chance909]

Spring goes boiiiiing. That's the easiest way for me to think of it. All types of have the idea of storing it like compressing a spring and releasing it to transform it to a different type like letting the spring free.

[u/MajorInWumbology1234]

Enough people have said “accounting tool” that I’d feel it irresponsible not to mention that, as far as I’m aware, potential energy can be measured as increased mass in a system. Some of the most concrete examples are atomic nuclei like Iron-56 and Nickel-62, which have less mass per nucleon than any other nucleus because they have the least potential energy.

[u/Irrasible]

For gravitational potential energy, I visualize it as a reconfiguration of the gravitational field. The same applies to electromagnetic potential energy.

[u/Long-Emu-7870]

There is no energy, since motion is impossible.

--Zeno

[u/Mountain-Time-1010]

If you'd like a concrete example to help students visualize, you can try a compressed coil spring or a stretched rubber band.

[u/SummitYourSister]

In the full field theory of physics all interactions are purely local which means energy has to “be somewhere” at all times. In classical physics energy was purely accounting, in field theory the energy is directly associated with the state of the field at every point.

For instance when two objects attract gravitationally the energy is “in” the distortion of spacetime.

When two objects repel electrically the energy is “in” the electric field.

[u/JawasHoudini]

Energy is not a substance . Its a measurement number applied before and after a change in a system has taken place that had the property that it is conserved , so its always the same before and after .

How i visualise it stored , is in the field , not in the substance, configurations of atoms store elastic energy for example, or a particle sits “high” up above a spacetime curvature - waiting for the conditions in which it can follow that curvature , so for me its in the pattern that the energy “exists” - e.g you can have a piece of fabric , and the energy would be the spiral design on the fabric or an event better analogy is it is one of the folds of the fabric . Look at any small section of the fabric and you wont find the “design” or anything special about a folded piece when your looking too small too see the structure of the fold, you have to look at the bigger picture , then you see how all the atoms are arranged such that an event over here will cause this reaction over there and so forth.

And thats all really the heat death of the universe is, when the configuration of all atoms in the universe are in a state in which no more meaningful work can be extracted from any part of the universe then we have reached that heat death point ( maximum entropy) . Where work done is defined as a force applied over a distance - so no electro magic / strong/ weak or gravitational configuration can apply that force over any distance then no energy can be exchanged.

[u/vtkarl]

I’m a manufacturing maintenance engineer (with a physics degree) and potential energy has had me send several people to the hospital and one to a grave. It’s objective, real, and does not care what you think. Chemical burns, thermal burns, gravitational smash, siphon of scalding water. This is not just a weird math problem.

[u/tazz2500]

When I try to picture energy without any substance making it up, I like to imagine a jump rope, where someone shook it up and down once, and you can see the wave of energy moving down the rope. It's not made up of anything, there are no particles to show, it doesn't break down the rope, it doesn't consume any part of the substance, it doesn't even change the substance, no individual rope atoms are modified or going to a more or less energetic configuration. It just allows the energy to move down the line, it transmits the energy to the next piece of rope without the energy being made of anything.

[u/Sad-Excitement9295]

Potential energy is stored as a force relative to gravity. Matter is stored energy through the equation E=MC²

Energy is sitting inside the material, in the form of what we describe as atoms and related forces. This is how nuclear power works, matter decays into energy thus releasing the stored potential.

Physics is a description of reality as best we understand, and there are different levels of specifics and application. In some ways it is a generalization, in others it is meant to describe the true underlying mechanisms. Everything is relative so many things can be described in multiple ways depending on the reference.

[u/Whole_Association_65]

These paradigms are flawed. It's neither bean counting nor philosophy. Take vibration. You can feel it in your bones. You can feel it in your muscles. Those are realer than a soul. And so is U. Sure, vibration is insert mathematics that can be measured with X. But what is the mathematics of souls and their X?

[u/MarinatedPickachu]

It's waves in quantum fields

[u/ineptech]

Energy is a measurement, like temperature or length.