Richard Muller, physics professor emeritus at UC Berkeley, states that energy is the most difficult concept to understand in the basic physics curriculum. It will be interesting to see what people say.

I suspect that what the "Western world thought about energy and energy transfer" was confined to a fairly small number of people. It isn't that the 99% who weren't thinking about energy were simpletons. Rather, modern uses of energy (radio, electric light, etc.) didn't require any thinking at all. They were presented as boxes with knobs that you could turn on, a switch on the wall you could flip. Voila! Sound and light! Amazing.

I may be an idiot because I was astonished to learn (recently) that "electrical energy does not travel though the wire as sound travels through air but instead always travels in the space outside of the wires. This is because electric energy is composed of electric and magnetic fields which are created by the moving electrons, but which exist in the space surrounding the wires." This is excruciatingly non-intuitive. "Of course electricity travels right down the wire!" one would think.

During the 20th century, the particles and energies that compose the atom were discovered. I don't know whether the nature of atoms is intuitive or not -- it's pretty much over my head. The electron and energy I sort of get, ut the subatomic Higgs Boson giving mass to objects--nope, totally incomprehensible.

That's all OK: Most people (most of the time) can go through life innocent of that kind of knowledge. Not saying they should, but they can.

Most of us are dealing with the product-form of the theory. There may be quantum actions going on in my phone's processing chip, but I do not need to know about it. Like as not it would take me forever to understand those quantum goings on. We quickly adapt and soon take for granted world-wide networks (the Internet).

Once war was declared between the Allies and Central Powers in 1914, English ships immediately severed critical cables between Europe and England to make sure that Germany and the AH Empire would be would be incommunicado with the rest of the world. So, 105 years ago, [at least some] world-wide networks wee already routine.

Richard Muller, physics professor emeritus at UC Berkeley, states that energy is the most difficult concept to understand in the basic physics curriculum. It will be interesting to see what people say. — jgill

I think the closest thing that people can understand is BHP, break horse power (with motors) or simply horse power. They can imagine a horse pulling a cart. And that's it.



Very few remember the definition of energy or what joule stands for. Or that 1 watt is 1 joule per second. Those that have to ponder about electric devices or pay the electricity bill might be more aware of the underlying terms. And engineers are different in this case also. Yet even economics, social sciences or in business energy naturally pops up. Just like it does in physics. Yet Richard Muller might be right, just as it's hard for an economist to fathom just what gross domestic product actually is.

Me two cents ...

As per my high school physics sutra, energy is the capacity to do work. No energy, no work; explains why we have to eat almost continuously every single day.

The problem with energy is that it's not 100% efficient i.e. input > output, input - output = heat energy (waste + requires cooling, a headache).

The beauty of the Western take on how nature gets things done is that we can make accurate predictions e.g. how long your cell phone's battery'll last if you use this/that features on it. I consider that a marvel of Western science. That is to say there's no reason why the Western view of energy should be overhauled unless, of course, the inexplicability of so-called dark energy that allegedly drives cosmic inflation/expansion means we have to.

As per my high school physics sutra, energy is the capacity to do work. — Agent Smith

Now consider the difference between kinetic energy and potential energy. The former would be actually having the capacity to do work, and the latter would be having the potential to have the capacity to do work. The concept of "potential enrgy" really doesn't make any sense logically, but the use of it is what gives rise to the issue points us toward, where energy is seen as an entity in itself, rather than the property of an active object. When a thing has potential energy, that energy can only be understood as the property of something else. But it's easier just to ignore the requirement of something else, allowing the energy to exist as an abstract entity.

A rock perched on a ledge 300 ft above the valley can do something - kill/maim/destroy/etc. "By virtue of what?" asked the scientist.

It's gravity, but gravity is understood as the property of another object. If you remove the other object which the gravity is the property of, then you have energy as an independent entity, existing as a property of space.

Around the period of major advances in technology such as radio, the automobile, the electric light bulb in the late nineteenth and early twentieth centuries, do you think there was a change in how the Western world thought about energy and energy transfer? Like from the eighteenth century onward, there seemed to be this conception that energy represented something an object possessed – as a person possesses physical energy, or a ball has energy when airborne – and at some point when theory about light, electricity, time, and space, began to predominate over simple mechanics it seemed that a transition took place from energy being thought of as a property of an object into it being thought of as an abstract entity itself that could be part of a wave or motion between atoms; something that could be harnessed and stored. — kudos

I don't think that this latter transition happened as you describe it. Energy is not thought of as being an entity in its own right, as opposed to a property like mass. What happened over the past three centuries was that physical ontology has been expanded to include not only tangible objects of direct experience, such as billiard balls, but also theoretical entities such as microscopic particles, fields, chemical bonds, and so on. Those entities can still possess energy in more-or-less the same sense in which billiard balls and such possess energy, although the laws of energy transfer can differ:



Sometimes people use the word "energy" as a shorthand for some of those intangible entities, in particular electromagnetic fields. But it is the field that possesses the energy, in addition to all its other characteristics.

Ok, but what about chemical energy, allegedly resides in the bonds between atoms?

The concept of "potential enrgy" really doesn't make any sense logically, but the use of it is what gives rise to the issue↪kudos points us toward, where energy is seen as an entity in itself, rather than the property of an active object. When a thing has potential energy, that energy can only be understood as the property of something else. But it's easier just to ignore the requirement of something else, allowing the energy to exist as an abstract entity. — Metaphysician Undercover

I don't know if I agree with this. If I had a mechanical clock with a spring windup mechanism and it was fully wound, I would say the potential energy was within the clock, and in particular, within the wound spring. I wouldn't suggest it was floating within the clock or that it was somehow extractable from the spring so that it could exist separate and apart from the spring.

Potential energy is part of an analysis of a state of things wrt all the possibilities associated with that state.

The formula is always something like:

potential energy = kinetic energy times resistance

So the less resistance (like a penny falling through air instead of honey), the bigger the kinetic energy in the event (the penny goes fast instead of slowly). It's the same potential, though, matter what the resistance is.

What part of my post is this responding to? I'm not asking this dickishly, but I don't see how that responded to it, but it could have, but I just don't see it.

What part of my post is this responding to? I'm not asking this dickishly, but I don't see how that responded to it, but it could have, but I just don't see it. — Hanover

You said the potential energy is in the spring (or at least you seemed to.). Strictly speaking, potential energy doesn't have a location. You could think of it as a sophisticated prediction.

You said the potential energy is in the spring (or at least you seemed to.). Strictly speaking, potential energy doesn't have a location. You could think of it as a sophisticated prediction. — frank

I don't understand this. If it exists nowhere, it doesn't exist.

A battery has stored energy and you can move it from one thing to the next. I get that the total energy equals the potential energy plus the kinetic energy and the amount of energy that is demanded will increase based upon the resistance, but I don't see how we can suggest the energy is being expressed or being held in a potential state at some location away from the event.

That is, when I drop a penny, the energy event isn't occurring down the street.

I don't understand this. If it exists nowhere, it doesn't exist. — Hanover

It's a quantity.



I have a theory about why this seems counter intuitive. I think we have a sense of physics informed by emotions and sensations. We all know what it's like to have pent up energy and we know where it's located from sensations. We use this to understand physics.

Now consider the difference between kinetic energy and potential energy. The former would be actually having the capacity to do work, and the latter would be having the potential to have the capacity to do work. The concept of "potential enrgy" really doesn't make any sense logically, but the use of it is what gives rise to the issue↪kudos points us toward, where energy is seen as an entity in itself, rather than the property of an active object. When a thing has potential energy, that energy can only be understood as the property of something else. But it's easier just to ignore the requirement of something else, allowing the energy to exist as an abstract entity. — Metaphysician Undercover

This is where language fails us in terms of clarity. The terms ‘kinetic’ and ‘potential’ refer to particular qualitative relations. Kinetic is a quality of the work (movement), whereas potential is a quality of the capacity (unrealised).

The way I see it, ‘energy’ is the relation between capacity and work. We often attribute it to objects or events as property or possession, but that just helps us make useful sense of the relational structure.

You said the potential energy is in the spring (or at least you seemed to.). Strictly speaking, potential energy doesn't have a location. You could think of it as a sophisticated prediction.
— frank

I don't understand this. If it exists nowhere, it doesn't exist.

A battery has stored energy and you can move it from one thing to the next. I get that the total energy equals the potential energy plus the kinetic energy and the amount of energy that is demanded will increase based upon the resistance, but I don't see how we can suggest the energy is being expressed or being held in a potential state at some location away from the event.

That is, when I drop a penny, the energy event isn't occurring down the street. — Hanover

‘Doesn’t have a location’ doesn’t necessarily mean ‘exists nowhere’, it could mean the location is undefined. An electron, for instance, doesn’t have a single location as such - it is attributable to an atomic structure, sometimes several at once, and its location is relative. And when you drop a penny, the resulting energy event isn’t confined to the penny (an echo may be occurring down the street). The location is probabilistic, fuzzy, undefined - a predictive relation. You could attribute the energy event to you, to the penny, the sidewalk, etc. Most importantly, it exists relative to an observation/measurement event.

Potential energy as a sophisticated prediction makes sense to me.

You said the potential energy is in the spring (or at least you seemed to.). Strictly speaking, potential energy doesn't have a location. You could think of it as a sophisticated prediction. — frank
I don't understand this.If it exists nowhere, it doesn't exist. — Hanover

Aristotle's differentiation between Potential & Actual, as two different ways to exist, may help you to understand the same distinction in Physics. You could say that Potential is universal and non-local, while Actual is specific and local. For example, a AA battery is said to have the Potential for 1.5 volt-amps of current, even when no current (kinetic energy) is flowing. In a sense, the potential is stored in what physicists now call a "Field" (the universe as a whole).

Electrons bound to the field (entangled) are labeled as "Virtual" (essential ; wavelike), to distinguish them from Actual electrons flowing as causal current in a material substrate. In a battery, the electrons are bound to atoms as chemicals (inactive potential energy), but when "flowing" they are what we call "free" or Active or Actual Energy (particular ; pointlike). Potential Energy (virtual existence) has the ability to do work in the future, but is not currently causing change (actual existence).

You'll just have to get used to the idea of two kinds of existence : Real (particular ; physical) and Ideal (holistic ; potential). Warning, some won't like the metaphysical implications of this duality of Energy & Matter. :smile:


Potentiality and actuality :
The actuality-potentiality distinction in Aristotle is a key element linked to everything in his physics and metaphysics.. . .Aristotle describes potentiality and actuality, or potency and action, as one of several distinctions between things that exist or do not exist. In a sense, a thing that exists potentially does not exist, but the potential does exist. . . . Actuality comes from Latin actualitas and is a traditional translation, but its normal meaning in Latin is 'anything which is currently happening'. . . . The two words energeia and entelecheia were coined by Aristotle, and he stated that their meanings were intended to converge.
https://en.wikipedia.org/wiki/Potentiality_and_actuality
Note -- When Aristotle says a thing "does not exist", he means as a material object. So Potential existence is what we today would call "statistical probability", but Ari refers to it as "Form" (mathematical structure as opposed to material structure).

Electron Flow :
Because these virtually unbound electrons are free to leave their respective atoms and float around in the space between adjacent atoms, they are often called free electrons.
https://www.allaboutcircuits.com/textbook/direct-current/chpt-1/conductors-insulators-electron-flow/

And yet, something like visible light can 'travel' several hundreds of thousands of miles through a vacuum as a potential, never touching matter as we know it, finally reaching our retinas or photographic equipment only to affect us with the sights and images we call reality. I find that challenging to grasp with the classical intuition. There seems to be a new and different type of intuition being formed there. A physical effect emerging from the self-reflexive nature attributed to the potential. I think it really breaks down the divide there a lot. For instance, is kinetic energy something that exists in the sense of being 'out there,' when we look more deeply into it and find there are a number of potentials being fulfilled and unfulfilled based on how it is being observed? It's almost like the physical world is affected by a sort of creativity.

I don't know if I agree with this. If I had a mechanical clock with a spring windup mechanism and it was fully wound, I would say the potential energy was within the clock, and in particular, within the wound spring. I wouldn't suggest it was floating within the clock or that it was somehow extractable from the spring so that it could exist separate and apart from the spring. — Hanover

If you followed what Frank said, you might start to see why I said "potential energy" really doesn't make any sense logically.

Consider, the definition of energy stated by , "the capacity to do work". As a "capacity", this means energy is fundamentally a type of potential. Now we qualify that with "potential", and we have the potential for a potential. Of course two potentials don't make something actual, but what does it make? What sense can you make of 'the potential for a capacity (potential)'? Is it the possibility of a possibility? But let's start simple, what type of existence can a potential be said to have, in the first place?

Nice!

Potential energy is simply stored energy we can tap. The word "potential" isn't to be understood philosophically, as antipodal to actual (vide Aristotle). What sayest thou? Just a poor choice of words, a misnomer, or a clue that something's not quite right?

Like from the eighteenth century onward, there seemed to be this conception that energy represented something an object possessed – as a person possesses physical energy, or a ball has energy when airborne – and at some point when theory about light, electricity, time, and space, began to predominate over simple mechanics it seemed that a transition took place from energy being thought of as a property of an object into it being thought of as an abstract entity itself that could be part of a wave or motion between atoms; something that could be harnessed and stored.

I find it interesting from the point of view of how the conceptual landscape has changed along with this change. What kind of ways has the same shape been observed in other forms of everyday life in Western culture? Do you think there were any ways in which this may have influenced our way of thinking? — kudos

Western humanity has (for many hundreds, perhaps thousands, of years) thought or conceived of energy as being something that could be harnessed; but those were concepts previously understood by only a few, more well-studied individuals. You could say that what changed were these "new thoughts" becoming more commonplace within society, with the physical objects (such as the electric light bulb) acting as "proof" for the everyday person.

Usually the concept of work relates to a change of energy, kinetic or potential. When an object follows a path through a force field, if that field is conservative, the path the object takes from point A to point B is immaterial regarding work; all such paths produce the same work. This idea aligns with Cauchy's Theorem in complex analysis.

The analogy I recall is two people about the same weight standing before a mountain. One takes off directly to the summit over a series of cliffs, and the other follows a trail that winds round and round the mountain, finally reaching the top. Both have done the same work.

A sequence of smooth contours in the complex plane I devised that start at zero and end at one grow longer and longer without bound while converging uniformly to the straight line path along the x-axis from zero to one. Set in the backdrop of a conservative force field an object moving from zero to one along the x-axis does the same work as on a contour that could be unraveled and stretched from Earth to Alpha Centauri and beyond.

Potential energy is simply stored energy we can tap. The word "potential" isn't to be understood philosophically, as antipodal to actual (vide Aristotle). What sayest thou? Just a poor choice of words, a misnomer, or a clue that something's not quite right? — Agent Smith

Potential energy is energy relative to a thing's position. Kinetic energy is energy relative to a thing's activity. Clearly there is a very substantial difference between kinetic energy and potential energy.

Usually the concept of work relates to a change of energy, kinetic or potential. When an object follows a path through a force field, if that field is conservative, the path the object takes from point A to point B is immaterial regarding work; all such paths produce the same work. This idea aligns with Cauchy's Theorem in complex analysis. — jgill

This may be true of potential energy, but since kinetic energy relates to the specific activity itself, we cannot say that the path the object takes is immaterial. And this is why potential energy and kinetic energy are essentially non-convertible, due to unaccountable losses like friction, etc., what is called entropy, so we have no perpetual motion. But the law of conservation might pretend that they are convertible.

Potential energy is energy relative to a thing's position. Kinetic energy is energy relative to a thing's activity. Clearly there is a very substantial difference between kinetic energy and potential energy. — Metaphysician Undercover

The beauty, if I could call it that, is this: if the potential energy of a rock is 6 Joules, what it does/can do is fully accounted for by these 6 Joules it reportedly possesses.

The confusion that tends to arise is between what energy is and what the energy we use is. What we are concerned with is energydifference. The location of the energy difference is what is confusing about the potential energy of the rock at the top of the cliff, and it is between the rock at the top, and the potential rock at the bottom. Attach a rope and pulley to the rock and its descent can be contrived to do some work, if the rock is a long way from the edge, the work of getting it to the edge would be more than the work derived from its potential energy.

The beauty, if I could call it that, is this: if the potential energy of a rock is 6 Joules, what it does/can do is fully accounted for by these 6 Joules it reportedly possesses. — Agent Smith

As I said, there is no equivalence, due to entropy, which is the supposed "energy" which is unavailable, neither potential nor kinetic.

As I said, there is no equivalence, due to entropy, which is the supposed "energy" which is unavailable, neither potential nor kinetic. — Metaphysician Undercover

The math adds up is what I'm saying and that's an awesome achievement - civilization was built on energy so understood! As for entropy, measurable as heat (?), this too is part of the equation where the left hand side (potential energy) = right hand side (kinetic energy + heat/entropy). Am I wrong? Where's a physicist when we need one, eh?

↪Gnomon
And yet, something like visible light can 'travel' several hundreds of thousands of miles through a vacuum as a potential, never touching matter as we know it, finally reaching our retinas or photographic equipment only to affect us with the sights and images we call reality. I find that challenging to grasp with the classical intuition. There seems to be a new and different type of intuition being formed there. A physical effect emerging from the self-reflexive nature attributed to the potential. I think it really breaks down the divide there a lot. For instance, is kinetic energy something that exists in the sense of being 'out there,' when we look more deeply into it and find there are a number of potentials being fulfilled and unfulfilled based on how it is being observed? It's almost like the physical world is affected by a sort of creativity. — kudos

Yes. The key distinction between Potential Energy and Actual Energy is Inter-action. I think of Energy as a form of Information. In its statistical state, light Energy does not exist physically, hence is invisible. But when it interacts with Matter, Energy causes a change of form. Invisible mathematical Potential becomes visible Actual, a real state of matter in motion (Kinetic Energy). That's why massless light energy can travel through dark empty space imperceptibly & unchanged until it meets a physical object, and is reflected into a visual receptor.

For example, in the eye, the statistical potential of light energy transforms from a non-local wave of potential into particular photons which interact with the chemical Rhodopsin to produce a flow of electrons, which in turn, cause the brain to produce an image of whatever object the light last interacted with (reflected from). In other words, it communicates information about that object. But the mental image itself is subjective, and possesses none of the material substance of the object. That's what I call a creative act. Something new has been created, which did not exist before. But its existence is Ideal, instead of Real.

Heisenberg explained the counterintuitive nature of quantum physics in terms of "a subjective element in the description of atomic events, since the measuring device has been constructed by the observer, and we have to remember that what we observe is not nature in itself, but nature exposed to our method of questioning". Or, as Kant noted, we never know the ding an sich [thing itself] but only our mediated perception of the thing. John A. Wheeler described that "breakdown of the classical divide" between Real & Ideal, or Potential & Actual, in terms of a "participatory universe", in which the observer is a ["self reflexive"] part of the thing observed. Some have interpreted that participation to mean that the observer, "contrary to classical intuition", creates his own version of Reality. I wouldn't take that notion literally -- as Many Worlds proponents do -- but it might help to think of it as an as-if model of "complementary reality" as Bohr put it. It's a way to see both sides of the real/ideal coin simultaneously. :smile: