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In many discussions over the years its come to my attention that most physics enthusiasts, and even some professional physicists, don't know what energy is. That's why I'm asking the question What do you think energy is and why do you believe that? I'm asking so that I can learn what people here think it is so that we can come to understand the correct meaning of the term energy. By the correct meaning I'm talking about how I describe it on my website. Please understand that I'm not being arrogant by any means. I say this because I've studied the subject in depth, read several articles from physics texts and journals and from prominent physicists such as Richard Feynman, Sheldon Glashow, A.P. French, John Stachel, Alan Guth, etc. A solid study of the subject shows exactly what is meant by the term energy. That's how I came to write my webpage on the subject. All I did was take what has been described and explained by these brilliant well-experienced first rate physicists and put it in my own words.My goal is that we all come to have the same understanding of energy so that when we discuss something dealing with it we won't have to worry about its meaning like what happened recently. Thanks for your contribution. Please take note of whose posts I can't see.
I think energy is just a word, a word we use because we don't actually understand what energy is, so we give it this group name of energy. Energy is a group name that contains sub groups.
Light is fundamental magnetic energy represented by a vibration of an area of flux/current that can move through space effortlessly. If it interacts with neutron matter it can transfer the vibration energy by increasing the matters temperature.
Quote from: TheboxI think energy is just a word, a word we use because we don't actually understand what energy is, so we give it this group name of energy. Energy is a group name that contains sub groups.Thanks for answering half the question. However, it's not at all helpful to me if you only say what you think energy is. It's more important to me to explain why you think its that way. In fact that's what I really want to know, i.e. why people think energy is what they believe it to be. Many people have very different beliefs about what energy is. My goal is to learn why. Therefore stating only what you think it means is totally useless to me.Note: I modified the question so as to extract unhelpful and irrelevant comments. Also, I found a wonderful book online all about energy for those who are interested: Energy: A Beginner's Guide by Vaclav Smil. It can be downloaded for free at: ...sorry, you cannot view external links. To see them, please
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Matt Strassler; ...sorry, you cannot view external links. To see them, please
REGISTER or LOGIN says:“Energy is something that photons have; it is not what photons are.”
Light is an electromagnetic (EM) wave whose wavelength lies in the range 390 to 700 nm. Most of the energy in an EM wave is in the electric field component. An EM wave cannot interact with neutrons because their charge is zero and are therefore unable to interact via the electromagnetic interaction. I.e. neutrons cannot couple to an EM field.
Why do I believe this? Cause the very wise physicist Feynman believes that, and trust me; that dude knows what he's talking about!
Have you read or watched his lectures?
I'd point you to chapter 4-1 if you haven't. It'll give you a good sense of what I'm talking about!!!
 The Feynman Lectures on Physics, Vol I, Feynman, Leighton, and Sands, Addison Wesley, (1963)(1989). Section 4-1 What is energy? page 4-1.
My own pet notion is that in the world of human thought generally, and in physical science particularly, the most fruitful concepts are those to which it is impossible to attach a well-defined meaning.
Of all the physical concepts, that of energy is perhaps the most far-reaching. Everyone, whether a scientist or not, has an awareness of energy and what it means. Energy is what we have to pay for in order to get things done. The word itself may remain in the background, but we recognize that each gallon of gasoline, each Btu of heating gas, each kilowatt-hour of electricity, each car battery, the wherewithal for doing what we call work. We do not think in terms of paying for force, or acceleration, or momentum. Energy is the universal currency that exists in apparently countless denominations. The above remarks do not really define energy. No matter. It is worth recalling once more the opinion that H.A. Krammers expressed: “The most important and fruitful concepts are those to which it is impossible to attach a well-defined meaning.” The clue to the immense value of energy as a concept lies in its transformation. It is conserved – that is the point. Although we may not be able to define energy in general, that does not mean that it is only a vague, qualitative idea. We have set up quantitative measures of various specific kinds of energy: gravitational, electrical, magnetic, elastic, kinetic, and so on. And whenever a situation has arisen in which it seemed that energy disappeared, it has always been possible to recognize and define a new form of energy that permits us to save the conservation law. And conservation laws, as we remarked at the beginning of Chapter 9, represent one of the physicist’s most powerful tools for organizing his description of nature.
To further clarify matters, I should really give you a precise definition of energy. Unfortunately, I can't do this. Energy is the most fundamental dynamical concept in all of physics, and for this reason, I can't tell you what it is in terms of something more fundamental. I can, however, list the various forms of energy - kinetic, electrostatic, gravitational, chemical, nuclear - and add the statement that, while energy can often be converted from one form to another, the total amount of energy in the universe never changes. This is the famous law of conservation of energy. I sometimes picture energy as a perfectly indestructible (and unmakable) fluid, which moves about from place to place but whose total never changes. (This image is convenient but wrong - there simply isn't any such fluid).
Since I wrote that I've been wrestling with the common definition where most physicists claim that energy is defined as the ability/capacity to do work.
agyejy posted some interesting observations. Now John tell me where in the post the supporting evidence for the assertion that the electron is a knotted photon was made. I can't see it.
The energy and the electric and magnetic field components of a photon in free space are equal. Here is a reference:
Tellingly John what you neglected to post was the next paragraph from Pete's page."How seriously must we take the physical existence of this energy? No more and no less than any other bookkeeping practices. The physical quantities are those such as the EM field."To neglect this paragraph is to misrepresent Pete's intention for your own ends. That is not an honest way to promote your case.
Show me where in this article where the Poynting vector is spinning round and round an electron.
You try to make it look like you know what you are talking about by misrepresenting the work of others. This may be because you have no original work of your own to present.
Tellingly John what you neglected to post was the next paragraph from Pete's page."How seriously must we take the physical existence of this energy? No more and no less than any other bookkeeping practices. The physical quantities are those such as the EM field."
I believe that energy is a fundamental part of universal mechanics. The production of Energy in my opinion is a direct result of the behavior of chemicals interacting with each other to form anything from star systems to intelligent life forms.I feel that energy and purpose work together to deliberately form life. ( im a strong believer in the anthropic principle). The reason i feel this way about energy is i observe how my own body produces energy or indeed struggles to as the case maybeand i spend alot of time observing nature. My answer to this question is limited to a post big bang understanding. A little look at pre-big bang energy production might be interesting ;-)
Energy is an equivalence relation between different forms of potential for action.
I think is is a reasonable summary because energy is not 'stuff' that can be directly observed, it is a conserved attribute of the configuration of systems, indirectly observable in that configuration, and it is measured in terms of potential for action.
Why do I believe that? For the same reason that I believe a hammer is a device for hitting nails. We invent some tools to beat the universe into the shape we want, and others for describing how it works.
It appears that nobody understood what I was aiming at when I asked that question. I was attempting to ascertain where you learned it from, i.e. a text on thermodynamics, chemistry, journal articles, a combination of all of those, did you make it up yourself from your own genius, etc?
OK, it is what we were taught in school and have used ever since, because it is the definition used by every other scientist, just like engineers use the term "hammer" to denote a thing you use for bashing other things. And it turns out that every serious scientific text (as distinct from woo-woo, journalese or political mumbojumbo) uses the term energy to mean exactly the same thing. The fact that energy turns up in all sorts of forms is no problem - everything from the aural malleus of a weasel to the machine that turns a sheet of steel into a car body, is a hammer!
It is important to realize that in physics today, we have no knowledge of what energy is. We do not have a picture that energy comes in little blobs of a definite amount. It is not that way. However, there are formulas for calculating some numerical quantity, and we add it all together it gives “28” - always the same number. It is an abstract thing in that it does not tell us the mechanism or the reasons for the various formulas.
For example: it doesn't work for non-conservative systems. In such systems energy is defined but not conserved. An example is a charged particle in a time varying electromagnetic field.
If you want to play linguistics, you could start by claiming that momentum isn't defined - or even mass, for that matter. But we physicists try to build useful mathematical models of the universe rather than muck about with Aristotelian definitions, so if ∑mv turns out to be conserved, we give it a name because it is useful. Ultimately all scientific definitions tend towards "that which...." because science begins with observation. You could define hydrogen as "any number of atoms each of which consists of a single electron and a single proton" but some brilliant philosopher will point out that you haven't defined a proton, so chemists define hydrogen as "the element which..." and for most purposes it turns out that adding one or two neutrons doesn't alter its chemical characteristics, so it's a good definition - and applicable to all other elements too.Your nonconservative system is excluded from the definition I gave because it is not a closed system. Friction is a nonconservative force but in a closed system the kinetic energy of your car is entirely converted by brake friction into heat energy. If the energy of a closed (i.e. complete) system were not conserved, we couldn't calculate the temperature rise of the brake disc (or re-entry module), which is kinda important when you want to build a machine that can stop without melting. You might argue that the definition now becomes circular as I've effectively defined a closed system as one in which energy is conserved, but it isn't because we can in principle measure every element of that parameter.
... tell me how it applies to what you think energy is.
It sounds like you mean "The capacity to do work".
Quote from: dlorde... energy is not 'stuff' that can be directly observed, it is a conserved attribute of the configuration of systemsIn any case you've left out the defining quality of energy and that's it's property of being conserved.
... energy is not 'stuff' that can be directly observed, it is a conserved attribute of the configuration of systems