What Is the True Nature of Energy?

[Dale]

Did you change your message? I quoted you but the quote missed including the electron at rest question. Just wondering if I am doing something wrong in creating these posts?

Sorry about that. Yes, I did change my message. I try to do so quickly after posting if I make a change, but sometimes not quickly enough.

I see no work performed by an electron that has nothing to exert its force upon. However, the electron retains its ability to exert force upon another charge particle should that circumstance occur.

In other words, the sum total of the work done by the electron is 0, but it has the capacity to do work.

 

[James A. Putnam]

What other value besides 0 could I possibly put in for force in a situation with no force? I am only using your definition as you have stated it.

If you feel that I worked them out incorrectly then kindly work out the two examples I posted in the way that you intended your definition of energy to be used.

I did write a reply, it got lost. I am going back to reply again. However, I do not understand why you insist that the sum total of force times distance can only be calculated as an instantaneous event. In other words, zero force means energy does not exist. Obviously energy exists as the sum total of force times distance for a previously applied force that may not now be active. Why do you keep insisting that my argument is that kinetic energy disappears if a force is no longer active?

 

[James A. Putnam]

Sorry about that. Yes, I did change my message. I try to do so quickly after posting if I make a change, but sometimes not quickly enough.

In other words, the sum total of the work done by the electron is 0, but it has the capacity to do work.

In other words: An electron can cause another charged particle to acquire kinetic energy. Here again is that word capacity as if it removes energy from the example. Is capacity another word for force or not? I miss the empirical significance of the need for introducing the word capacity.

 

[Dale]

However, I do not understand why you insist that the sum total of force times distance can only be calculated as an instantaneous event.

Sorry I was not clear. By "absence of any external force" I meant that there is not now any force nor has there ever been any force acting on the mass/electron. I understood that you intended it to be a sum of previously applied forces so I set up the example in the complete absence of forces.

 

[Dale]

Is capacity another word for force or not? I miss the empirical significance of the need for introducing the word capacity.

"Capacity to do work" means that the system may currently not be performing work nor have ever performed work but it retains its ability to do work should the circumstance occur. It is just what you described above for the electron.

Similarly, if a bottle has a 1 L water-carrying capacity then it may currently not be carrying water nor have ever carried any water, but it retains the ability to carry 1 L of water should the circumstances occur.

 

[James A. Putnam]

Sorry I was not clear. By "absence of any external force" I meant that there is not now any force nor has there ever been any force acting on the mass/electron. I understood that you intended it to be a sum of previously applied forces so I set up the example in the complete absence of forces.

Ok. So you are saying that the electron is brought into existence without needing the application of force. I am not a physicist, but, I find that condition to be subject to debate. However, let's assume there is an electron as you stated and we know of no history of force being applied. I have no problem with that condition. The electron is the source, the cause, the exerter of force. Force begins somewhere before it is applied. I allow for charged particles to represent force without explanation. As I have stated in previous messages, we do not know what cause is and that includes me. I do not know what cause is. I only know what cause does. I do not have an explanation for the origin of cause. Personally, I think that charged particles can be accepted as known causes. Any attempt to explain the origin of their force would require explaining electric charge. I could speculate, but that is not appropriate here. I simply allow for force to exist before it is applied. Its existence is not dependent upon its application. An electron can exert force. I do not know why.

 

[Drakkith]

In other words: An electron can cause another charged particle to acquire kinetic energy. Here again is that word capacity as if it removes energy from the example. Is capacity another word for force or not? I miss the empirical significance of the need for introducing the word capacity.

I don't see how else you could word that sentence and include "energy" or "force" instead of "capacity".

 

[James A. Putnam]

I don't see how else you could word that sentence and include "energy" or "force" instead of "capacity".

Why not just say it has energy? Kinetic energy of an object is the result of applying a force across a distance, and, the carrier of that kinetic energy can apply force in turn? Yes the object has the capacity to apply force, but, the introduction of that word does not clarify the physical circumstances. Both force and distance are included in equations. Capacity is not inculded in equations. In any case, even if my view does not suffice for others, I still see words exchanged for words instead of sticking to that which we know of as empirical evidence. What we know empirically is that changes of velocity occur for unknown reasons. Fortunately, we do not have to actually know those reasons in order to set up conditions that make certain patterns in changes of velocity useful to us.

 

[Drakkith]

Actually my point was that we do not know what cause is. It was not a question where I answer it or anyone else needs to answer it. I brought that point up to make clear, my viewpoint, that definitions such as 'force is influence' are unhelpful. The answer, as I see it is that 'we do not know what force is'. I see no problem with recognizing that which is known versus that which is not known. Effects are known. Cause is unknown. My own response to 'What is energy?' is that the answer depends upon explaining force, but, we cannot explain force. Therefore, I added to the discussion, in effect, that we do not know what energy is. I still see no value in debating that the acceleration of a particle who's energy is constantly in existence and changing according to the sum of differential values of force times distance, is really not a measurement of energy. If the book answer is different, let the book answer rule. As for me, I will continue to look beyond answers that are formed from mere exchanges of words.
James

Isn't this like the whole point some of us has been trying to make? Science has specific definitions and meanings for everything. If you don't agree then you don't agree and there isn't anything we can do about that, which is fine. However if you are going to argue on Physics Forums, then you cannot say that science is wrong and expect to be taken seriously. YOU may say that it is not known what causes force or something, but according to Science there IS a cause. Don't misunderstand me, I completely recognize and agree with your point of view in that we don't know the "cause" of some things. Attempting to discuss that takes you beyond current mainstream science which is not something generally allowed here at PF because, as you can see from this thread, it typically gets out of hand.

 

[SpectraCat]

Addressing this in particular: "As you can see, the integral of "force times distance" is most assuredly NOT independent of past history .. it is *defined* by past history. The quantity represented by the integral of "force times distance" is called work in physics. Work is a *change* in energy of a system. "

I would appreciate your view on this: The integral of force times distance is independent of past history. That is why a constant force can be substituted to represent all examples of force times distance. That is why a constant force can be used to derive Einstein's energy equation.

My view on that is that it makes no sense at all .. at least not how you have stated it. First of all, let's look at the actual mathematical derivation of work, because the phrases we have been using to describe it (i.e. force times distance or even the integral of force times distance) are imprecise at best.

The equation for work is: W_C=\int _C\vec{F}\cdot d\vec{r}

What that integral means is, "The work expended over some arbitrary path C is the integral of the dot product of the force vector and the infinitesimal change in the position vector along all points on the path C." That is what I meant when I said you can't even calculate a value for work until you know the path that was taken. This is to be contrasted with the difference in energy between starting and ending points of that same arbitrary path C. That energy difference is a STATE FUNCTION! It always has the same value whether you take path C, or D or XYZ. That is why although work is a change in energy, and has the units of energy, it is not the same thing as energy. Seriously man, if you don't get this, just look at the thermodynamics chapter of your physics textbook, or even a decent college level chemistry textbook .. it will verify what I am saying and give more carefully constructed examples.

I have no idea what you are talking about when you mention "constant force" or "einstein's energy equation". Are you talking about E=Mc[sup2[/sup]? Because I am pretty sure he didn't use any sort of idea about "constant force" to derive that.

"Now you are perhaps getting the idea .. that last statement is close to correct ... work is the *PATH-DEPENDENT CHANGE* in energy as a force is applied to a system over a particular path. " I think I have the idea. Still, I would be interested in your explanation about why a change in energy is not a recognized as simply a change in energy, but rather, work?

I explained that above ... and I have explained it many times. I can only conclude that you don't understand what a state function is, and why a state function is different from a path-dependent quantity.

I put forward the view that energy and work have the same units because they are the same thing. Any differences are semantical. The introduction of the word 'capacity' for purposes of mediating between the two is, from my viewpoint, semantical. Still, if the book answer must be that they are different things, then let the book answer rule. However, they both result from the integral of force times distance and they both suffer from the unknown nature of force.

Sorry, but that is simply wrong, at least from the standpoint of physics. I and many others on this thread have tried to explain to you why it is wrong. If you don't understand our answers, perhaps you should take it upon yourself to do some more careful reading to better understand why what we are saying is correct.

Is there an instance where work occurs that I cannot equate every step, even infintesimal steps, with the existence of energy?

No there is not ... that is because work always involves a change in energy! On the other hand, changes in energy do not always involve work. In thermodynamics, the energy change for a given process is defined as the sum of heat and work exchanged. in that process. If no work is done, then the energy change is due ONLY to the exchange of heat. If the process is adiabatic (i.e. no heat exchanged), then the energy change is due only to the work expended during the process.

 

[James A. Putnam]

Isn't this like the whole point some of us has been trying to make? Science has specific definitions and meanings for everything. If you don't agree then you don't agree and there isn't anything we can do about that, which is fine. However if you are going to argue on Physics Forums, then you cannot say that science is wrong and expect to be taken seriously. ...

So you have not seen benefit in my argument that physics should give physic, meaning referring to physical properties, answers and not involve itself in word exchanges? If the book answers are the limitation of discussion, then, there is a point to my keeping my views elsewhere.

 

[Drakkith]

Why not just say it has energy? Kinetic energy of an object is the result of applying a force across a distance, and, the carrier of that kinetic energy can apply force in turn? Yes the object has the capacity to apply force, but, the introduction of that word does not clarify the physical circumstances. Both force and distance are included in equations. Capacity is not inculded in equations. In any case, even if my view does not suffice for others, I still see words exchanged for words instead of sticking to that which we know of as empirical evidence. What we know empirically is that changes of velocity occur for unknown reasons. Fortunately, we do not have to actually know those reasons in order to set up conditions that make certain patterns in changes of velocity useful to us.

In other words, the sum total of the work done by the electron is 0, but it has the energy to do work.

That doesn't make any sense according to the accepted definitions of energy. In any case, you know exactly what it means and you are just arguing to argue.

In any case, even if my view does not suffice for others, I still see words exchanged for words instead of sticking to that which we know of as empirical evidence.

Our definitions and explanations come directly from empirical evidence. In all these posts I still cannot see why you would disagree with that.

What we know empirically is that changes of velocity occur for unknown reasons.

What we know is that changes in velocity occur because objects exert force on other objects. We KNOW this. Attempting to argue that we don't know what force or charge or energy is just shows that you don't understand the limits of science. Science knows that it cannot define force except as something that causes a change in other objects. Attempting to explain what Force or Energy "actually is" is meaningless to science, because it cannot be observed in that context. Do you agree with that?

 

[Drakkith]

So you have not seen benefit in my argument that physics should give physic, meaning referring to physical properties, answers and not involve itself in word exchanges? If the book answers are the limitation of discussion, then, there is a point to my keeping my views elsewhere.

The issue here is that YOU think that our current way of explaining things doesn't give physical answers. At least not in a way you agree with. Science defines itself the way it does BECAUSE it is limited i knowledge, not despite of. That is why things get so specific in meaning. Energy is defined one way, while work is defined another way, no matter how alike the two might be, they are NOT the same thing according to science, so they are defined differently. And really, how can we define something without using other words? Force, time, distance, mass, ETC. That is why we have words in the first place. Without using these all our definitions would devolve down to saying "It's just something".

 

[James A. Putnam]

Spectracat,

I do understand. Your response was adamant. I don't need further clarification. You think that I do not know what I am talking about. I need to read and learn about physics and in particular thermodynamics. All of this because my position differs from yours.

"I have no idea what you are talking about when you mention "constant force" or "einstein's energy equation". Are you talking about E=Mc[sup2[/sup]? Because I am pretty sure he didn't use any sort of idea about "constant force" to derive that."

Please check it out.

"I can only conclude that you don't understand what a state function is, and why a state function is different from a path-dependent quantity."

I certainly do. However, I don't think that there is anything I can say about that here. For example, thermodynamic entropy is defined as a state function and its similarities to energy are often put forward to show that it is a state function. It appears that contesting what is or is not a state function would be out of line here.

"No there is not ... that is because work always involves a change in energy! On the other hand, changes in energy do not always involve work. In thermodynamics, the energy change for a given process is defined as the sum of heat and work exchanged. in that process. If no work is done, then the energy change is due ONLY to the exchange of heat. If the process is adiabatic (i.e. no heat exchanged), then the energy change is due only to the work expended during the process. "

I am very familiar with that circumstance. Whatever it has to do with disputing what I have said, I missed it. I do not say that the existence of energy always involves work.

 

[James A. Putnam]

Dakkith,

"That doesn't make any sense according to the accepted definitions of energy. In any case, you know exactly what it means and you are just arguing to argue."

Ok, I understand clearly where you are coming from. My questions and responses have no merit.

 

[Dale]

Ok. So you are saying that the electron is brought into existence without needing the application of force. I am not a physicist, but, I find that condition to be subject to debate. However, let's assume there is an electron as you stated and we know of no history of force being applied. I have no problem with that condition. The electron is the source, the cause, the exerter of force. Force begins somewhere before it is applied. I allow for charged particles to represent force without explanation. As I have stated in previous messages, we do not know what cause is and that includes me. I do not know what cause is. I only know what cause does. I do not have an explanation for the origin of cause. Personally, I think that charged particles can be accepted as known causes. Any attempt to explain the origin of their force would require explaining electric charge. I could speculate, but that is not appropriate here. I simply allow for force to exist before it is applied. Its existence is not dependent upon its application. An electron can exert force. I do not know why.

So now the question remains, how can we apply your definition of energy to the electron which has never experienced any force in order to get the correct mass energy of .5 MeV?

 

[Drakkith]

Dakkith,

"That doesn't make any sense according to the accepted definitions of energy. In any case, you know exactly what it means and you are just arguing to argue."

Ok, I understand clearly where you are coming from. My questions and responses have no merit.

When you are arguing that we can't use the word "capacity" in a sentence describing energy and work, yes.

 

[James A. Putnam]

So now the question remains, how can we apply your definition of energy to the electron which has never experienced any force in order to get the correct mass energy of .5 MeV?

I didn't get back to your original message concerning this. I will do that. But, in short form: Saying that energy is the sum of force times distance does not require action. There can exist a force that, if allowed to act, will act across a distance. Both that force and that distance exists prior to the event. Action is not required to justify the statement that energy is the sum total of force times distance. In the case of potential energy, that sum total has not yet been calculated because an event has not yet occurred. The force exists. I do not know what distance that force will be permitted to exert itself across. What ever that distance is, both that force and that distance exist prior to its use. The existence of potential energy is the recognition that a force exists and if that force is permitted to act upon an object for a given distance, then kinetic energy will result. The existence of kinetic energy is not required before the existence of force. Kinetic energy is an effect after the cause. We do not know what cause is. Patterns in changes of velocity are all that we have to learn from. The cause, or very speculatively 'causes', are given.

 

[James A. Putnam]

When you are arguing that we can't use the word "capacity" in a sentence describing energy and work, yes.

This word substitute represents physics to you?

 

[Drakkith]

This word substitute represents physics to you?

What are you talking about?

 

[James A. Putnam]

What are you talking about?

I am talking about your reliance upon the word capacity as if that clarifies the concept of energy. Energy is sufficient. It does not require other words. It is what it is. It already includes force either active or potential. I think I have asked something very much like this before: What is capacity if it is not force?

 

[Drakkith]

I am talking about your reliance upon the word capacity as if that clarifies the concept of energy. Energy is sufficient. It does not require other words. It is what it is. It already includes force either active or potential. I think I have asked something very much like this before: What is capacity if it is not force?

What do you mean energy is sufficient? The word energy has no meaning if you cannot define it, which requires words like capacity and work and such. Is that what you were saying or did I misunderstand you?

 

[Dale]

There can exist a force that, if allowed to act, will act across a distance. Both that force and that distance exists prior to the event. Action is not required to justify the statement that energy is the sum total of force times distance.

This is essentially what is meant by "capacity" to do work. As soon as you start talking about some X that may occur in the future given the appropriate circumstances you are talking about the capacity for X. That is why the definition of energy as the capacity to do work is important. You cannot get rid of the word "capacity" without introducing the same concept again, as you have demonstrated.

 

[James A. Putnam]

This is essentially what is meant by "capacity" to do work. As soon as you start talking about some X that may occur in the future given the appropriate circumstances you are talking about the capacity for X. That is why the definition of energy as the capacity to do work is important. You cannot get rid of the word "capacity" without introducing the same concept again, as you have demonstrated.

I can use the word force. Force is a real physics property.

 

[Dale]

If you are talking about possible forces that may be exerted in the future given the right circumstances then that is the capacity to exert force.

 

[Drakkith]

I can use the word force. Force is a real physics property.

No, you cannot use force as a subsitute for Capacity without completely altering the sentence. And this is about language and grammar now, not about physics.

 

[James A. Putnam]

What do you mean energy is sufficient? The word energy has no meaning if you cannot define it, which requires words like capacity and work and such. Is that what you were saying or did I misunderstand you?

Energy is a physics property. Borrowing words that do not exist in physics equations does not clarify those properties that are included in physics equations. I define energy as the sum total of force times distance. Due to earlier necessary clarification that sum total can exist actively as completed or it can exist potentially so that it can be completed at some future time. Energy, even though we cannot explain force, is sufficient in itself to explain itself. It is the sum total of force times distance whether active or potential. No we do not know what force is. The word capacity does not tell us what force is. It adds nothing to that which physics equations already tell us. Please define the word capacity so that it has relevance to physics equations? What I mean by this is: Capacity can either be included in physics equations or it has no place in explaining physics properties. There is no place for a property called capacity in physics equations. There is a place for both force and distance.

 

[SpectraCat]

Spectracat,

I do understand. Your response was adamant. I don't need further clarification. You think that I do not know what I am talking about. I need to read and learn about physics and in particular thermodynamics. All of this because my position differs from yours.

No, I made those comments because your posts don't make any sense, and it's not like I haven't tried to understand them. So you either don't understand these things, or you are unable or unwilling to communicate what the distinction is that you are trying to draw. You have provided precious little in the way of descriptive examples or references to back up what you are saying. You APPEAR to not understand why it is important that change in energy is a state function, while work is not. You APPEAR not to understand that your description of energy as "force times distance" doesn't make any sense in the context of physics, because "force times distance" (or more correctly the integral I indicated above) is the definition of work in physics. Are you saying that integral is NOT what you are talking about when you say "force times distance"? Then what is the mathematical formulation of your statement? Please give the equation. You have made a lot of vague phenomenological musings about "sum total of force times distance", but it is not at all clear what you mean.

"I have no idea what you are talking about when you mention "constant force" or "einstein's energy equation". Are you talking about E=Mc[sup2[/sup]? Because I am pretty sure he didn't use any sort of idea about "constant force" to derive that."

Please check it out.

Really? After all the work I and others have done to help you understand what we are saying? You can't be bothered to provide a clarification about a casual comment you made that appears to not make sense?

"I can only conclude that you don't understand what a state function is, and why a state function is different from a path-dependent quantity."

I certainly do. However, I don't think that there is anything I can say about that here. For example, thermodynamic entropy is defined as a state function and its similarities to energy are often put forward to show that it is a state function. It appears that contesting what is or is not a state function would be out of line here.

Well, you appear to be saying either that "force times distance" is not path-dependent (which makes no sense as I have already pointed out), or you are saying that energy is not a state function, which is flat out wrong.

"No there is not ... that is because work always involves a change in energy! On the other hand, changes in energy do not always involve work. In thermodynamics, the energy change for a given process is defined as the sum of heat and work exchanged. in that process. If no work is done, then the energy change is due ONLY to the exchange of heat. If the process is adiabatic (i.e. no heat exchanged), then the energy change is due only to the work expended during the process. "

I am very familiar with that circumstance. Whatever it has to do with disputing what I have said, I missed it. I do not say that the existence of energy always involves work.

Yes, you do .. because you are defining energy in the way work is defined in physics. You have already said that you consider work and energy changes to be completely equivalent in the context of physics, with the only difference being a semantic one.

 

[Buckleymanor]

What is energy.
Well let's suppose you take everything away but leave just a minute thing behind.
Gravity , Mass , Potential,light, force, distance,time,the thing you are left with is energy!

 

[Drakkith]

Energy is a physics property. Borrowing words that do not exist in physics equations does not clarify those properties that are included in physics equations. I define energy as the sum total of force times distance. Due to earlier necessary clarification that sum total can exist actively as completed or it can exist potentially so that it can be completed at some future time. Energy, even though we cannot explain force, is sufficient in itself to explain itself. It is the sum total of force times distance whether active or potential. No we do not know what force is. The word capacity does not tell us what force is. It adds nothing to that which physics equations already tell us. Please define the word capacity so that it has relevance to physics equations? What I mean by this is: Capacity can either be included in physics equations or it has no place in explaining physics properties. There is no place for a property called capacity in physics equations. There is a place for both force and distance.

Energy is a word, just like capacity. We use the word Energy to define something, JUST like we do with Capacity and Force and Mass and everything else.

Energy, even though we cannot explain force, is sufficient in itself to explain itself.

Explain Energy without using Force, Time, Distance, Mass, Velocity, or any other word. You cannot.

The word capacity does not tell us what force is.

Of course not. Why would it?

Capacity can either be included in physics equations or it has no place in explaining physics properties.

How can you explain equations without words?

You are either SERIOUSLY in need of education, or you are being ridiculously stubborn.

 

[Dale]

Due to earlier necessary clarification that sum total can exist actively as completed or it can exist potentially so that it can be completed at some future time. ... Please define the word capacity so that it has relevance to physics equations? .

Sounds like you have defined it reasonably well already.

 

[James A. Putnam]

"ou are either SERIOUSLY in need of education, or you are being ridiculously stubborn."

Oh, ok.

 

[James A. Putnam]

Sounds like you have defined it reasonably well already.

No I asked for you to define it so that it can be part of a physics equation. I did not define it. I simply passed that word along because it keeps boucing back as if it has a role to play in theoretical physics. What is its mathematical representation?

 

[James A. Putnam]

"No, I made those comments because your posts don't make any sense, .." My posts make sense.

 

[Dale]

No I asked for you to define it so that it can be part of a physics equation. I did not define it.

When you cast it in the form of a physics equation for your definition then I will do the same.

 

[berkeman]

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