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B Does all energy move?

  1. Sep 10, 2017 #51

    Bandersnatch

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    All those interactions, like gravity, EM, nuclear forces, produce force fields. If you then place a particle which interacts with a given field, within that field (e.g., an electron in an electric field), it will have potential energy associated with its position (not motion). It is stored in the configuration of the system. Changing the configuration either releases the energy in some other form, or requires input of some other form or energy.
     
  2. Sep 10, 2017 #52

    ZapperZ

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    I think that this is the root cause and the most fundamental problem with your understanding of "energy". You think that it is a "stuff" that must have some location or position. This is where you went wrong.

    Look at the gravitational potential energy (i.e. let's start with something SIMPLER and not jump right into the standard model). The gravitational potential and potential energy extends over all space that feels the gravity from that celestial body. So to ask for where it "resides" doesn't quite make sense. It is like asking for the location of the color blue.

    You need to look at the mathematics that represents these things that you are talking about. This is why you are not getting what we've been trying to tell you.

    BTW, just as a suggestion, if that was ALL that you understood about "the standard model", you should not keep using it as a crutch to explain things away, because it appears that you don't even know what it is.

    Zz.
     
  3. Sep 10, 2017 #53

    Drakkith

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    Arguably, nowhere. It's just "bookkeeping". Or one could say that it resides in the configuration of the system, but that's a slightly different take on the word "resides".
     
  4. Sep 11, 2017 #54
    Do you mean that the energy is embedded/locked up inside a field, and even though it’s not physically there (yet) for our eyes to see, and for our computers to be measured, it’s potentially there, conserved in the field, and this genie can come out of his bottle, so to speak? So this field didn’t generate energy out of nothing (of course not, that would be impossible), but it already existed, kind of 'locked up' behind/inside the field, and can be requested/called up?

    This leads me to an example question: how is the arrangement of atoms in for instance the molecule glucose, or the arrangement of alkanes in oil, holding potential energy, which by its shape contains more energy than the same amount of atoms in a molecule with another configuration? Glucose is like 'a ball on top of a hill', and glucose can be broken down that releases energy, just like a ball can 'fall down the hill' that gives energy. This ball obviously has gravitational energy, so the metaphor doesn't apply in the same way, because the potential energy of glucose has nothing to do with gravity, so what's the difference? Does glucose conserve its energy in this 'hidden' energy field, like a genie in a bottle? It is "stored in the configuration of the system", like you said?

    Glucose (C6H12O6) + 6 x O2 <--- can be broken/formed by ---> 6 x CO2, 6 x H2O + energy (photons). The difference of the two is heat energy. So the extra energy that’s locked up in the glucose molecule is not there to be measured (because it's not moving or anything), but is this also residing in a field the same way? Because the C atoms, H atoms or O atoms in glucose ar not all of a sudden in a different (or more excided) state than the same atoms when it's NOT glucose, right?

    Or is this a totally different case, and I'm way off track here by comparing them?
     
    Last edited: Sep 11, 2017
  5. Sep 11, 2017 #55
  6. Sep 11, 2017 #56
  7. Sep 11, 2017 #57

    jbriggs444

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    http://www.feynmanlectures.caltech.edu/I_04.html

    Pay particular attention to the statement in 4-1: "There are no blocks".
     
    Last edited: Sep 11, 2017
  8. Sep 11, 2017 #58


    Sugar in a sugar bowl, oxygen in the atmosphere. That configuration of molecules has chemical energy.

    A sugar beet plant somehow broke some chemical bonds, broken chemical bonds are chemical bonds that have energy, or contain energy, or whatever the correct wording is.

    (The sugar-beet broke bonds between oxygen and hydrogen and oxygen and carbon, producing oxygen and some hydro-carbons)

    There's "binding energy" in chemical bonds. Now, one might very easily get the idea that binding energy is energy, but it's negative energy.
     
    Last edited: Sep 11, 2017
  9. Sep 11, 2017 #59

    Drakkith

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    Quoting Feynman from the link:
    It's difficult to say where an abstract numerical quantity (or an abstract concept) that appears purely from certain calculations resides. Energy is not water. It is not rock. It is not an object or something that takes up space and it can't be said to occupy an area. You cannot touch it, taste it, hear it, or anything else. It is, arguably, nothing but number crunching. Arguably.
     
  10. Sep 12, 2017 #60
    So nobody has a clear definition of Energy?
     
  11. Sep 12, 2017 #61

    jbriggs444

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    It can be measured to quite a large number of significant figures. So yes, we have good operational definitions.

    Edit: We can tell you how much of it there is. But if asked about its "location" or its "velocity", we have to frown and say "what are you talking about?"
     
  12. Sep 12, 2017 #62
    To me it is the quantity that makes the world un-exploitable. For example, It can be kinetic energy so it better stay constant in a closed system. Luckily we found this quantity and used it. It is not an object or anything. It is a mere beautiful idea and concept.

    Why isnt this enough?
     
  13. Sep 12, 2017 #63

    Drakkith

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    Clear? Yes. Clear AND easily understood AND makes intuitive sense? Not by a long shot.
     
  14. Sep 12, 2017 #64
    I think the crux of the OP surrounds the definition of Energy.

    My own background is in Mechanical Engineering so for me I use the idea of Energy to work out how thinig do or dont deform, how things move or how to make them move in a prticular way, that kind of thing. So I know how to use the concept of Energy but reading through this thread it occured to me, I couldn't give a clear definition that didn't end up sounding really hand wavey & vague.
     
  15. Sep 12, 2017 #65

    Drakkith

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    Indeed. I think of energy as describing something about the overall configuration of a system. The details about what that something is is usually not needed. If I'm using a laser and a CNC machine to cut through metal sheets, I don't care about exactly which atoms get excited and what happens to them. I only care about the larger-scale results, namely the thickness that the laser will cut through, which can be predicted using energy equations.

    I find it extremely interesting that energy equations can be used for both large-scale and small-scale applications. Properties of everything from subatomic particles to planetary systems (and larger scales) can be predicted using energy equations.
     
  16. Sep 12, 2017 #66

    russ_watters

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    Maybe....not sure why you criticized us for not answering before posing the question, but anyway...

    I think people have more trouble with the definition of energy than they should. Yes, the dictionary definition is broad/vague, but that's just because there are a lot of different types of energy and it is tough to tie them all together into one definition. I suspect though if people put the same amount of thought into the definition of "car", they'd realize it has similar issues of specificity that don't bother them.

    So how do we get past this? By defining all the different types of energy separately and then just tying them together loosely with the standard definition or conservation of energy/Noether's theorem. Take kinetic energy:
    Kinetic energy is energy due to motion as defined by KE=.5mv2 It's simple and defined precisely via the equation. It's much more straightforward than the definition of energy itself. And:
    I think it it should be enough that it is a useful mathematical relation between certain properties/parts of a system. "KE" is a mathematical relation that was discovered and is useful and is mathematically equal to the other mathematical relations that we therefore bundle together under the header "energy". It doesn't need to be an object (other than a mathematical object) and doesn't need to reside anywhere specific in order to be real (similarly: where is your speed? heck: where is your money?).
     
  17. Sep 13, 2017 #67
    I think energy is not just a concept, it is a feature of the nature of the world. That the world has a nature one may argue but assuming it does, then energy is a feature of it. If you take all possible worlds you can restrict them by using laws. All those possible worlds that don't follow a give law you eliminate. There are possible physical worlds like ours in all ways except that they do not allow one to define energy as we do. Our world does. The fact that it does is not the concept of energy - it is the fact of it. What fact? There are many but suffice to say our world does not allow interactions between physical entities that do not conserve a certain quantity within certain probabilities and for certain times. This is true using the classic, quantum mechanical, and relativistic notions of energy. Even if you do not admit that the world has a nature you will still admit that the concept of energy is more than just a concept because it constrains the type of your sensory experiencing.

    You can have the concept of energy and live in a world where its definition does not apply. We live in a world where it does apply. Its not just an idea.
     
  18. Sep 13, 2017 #68
    Curiosity.

    Yes me too. What facinates me most is the conversion of Energy from one type to another, that this quantity is so easily exchangeable.

    It wasn't meant in a critical manner, my apologies if I came across that way.
     
  19. Sep 13, 2017 #69

    Drakkith

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    I doubt that the concept of energy would have been created in a universe in which it does not apply. We created it solely because it is a useful concept that greatly simplifies certain physical problems and can, in some cases, offer an explanation solely in terms of itself.

    On the question of whether energy "really exists" or not, I neither know nor care. Neither possibility changes physics in any way.
     
  20. Sep 13, 2017 #70
    I think this question is interesting, but needs refinement. Imagine a scalar field where at each point energy is measured. I assume the question is whether such a field can be space independent over a certain neighborhood...I mean I know this is true for zero point energy in a vacuum and certain QFT systems.
     
  21. Sep 13, 2017 #71

    DrClaude

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    This thread is devolving into a series of personal interpretations of what energy is. Time to close.
     
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