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So what is ENERGY?

  1. Jan 16, 2008 #1
    As an introduction to this physics forum, let me begin by asking:

    What is energy?

    Is Energy something tangible or is Energy only apparent when certain base characteristics belonging to the topological composition of our universe interact or you may have another idea in mind which can play out in the real world?

    Yes welcome to our universe :smile:
  2. jcsd
  3. Jan 16, 2008 #2


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    Your post is mostly word salad. You're using words like "topology" incorrectly, for example.

    Energy is just a number we assign to a system to quantify its ability to perform work. No more, no less.

    - Warren
  4. Jan 16, 2008 #3
    Sometime, the energy is MORE than ability to perform work. For example, if thermal energy is Q, the ability to perform work is only Q*(T2 -T1)/T2
  5. Jan 16, 2008 #4
    wordsalad or not, the ability to perform work is a simplified explanation to an observation that we make on a regular basis. doing things like increasing the mass of an object containing kenetic energy. manufacturing matter from apperantly nothing... bending the fabric of space...

    the question I often ponder is how does the energy given to a base ball in the form of kenetic energy be a direct realitive to the material of the baseball.

    of course my cheese may have slipped off my cracker with this post!
  6. Jan 16, 2008 #5

    Claude Bile

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    Energy is DEFINED as "the ability to do work".

    The ability to do work is in turn determined by the current state of the system in question. Gravitational PE depends on the distance from a mass (or masses). KE depends on velocity, etc.

    There is nothing in our current model that suggests energy consists of some "stuff" which seems to be an idea that persists in this thread.

  7. Jan 16, 2008 #6


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    "topological composition of our universe interact"?? I've taken topology and I can't make heads or tales out of that. I can't even determine whether "interact" here is supposed to be a verb or a noun. I would think of "interact" as a verb, but that doesn't make grammatical sense here.

    Basically, "energy" is a bookkeeping device. In basic kinematics, with simple "perfectly elastic" collisions, it was recognised that a particular combination of variables, (1/3)mv2, "kinetic energy", remained the same and so "conservation of energy" became a good rule for solving such problems. Add changes in height and you had to add "potential energy" to "balance" the equations. Add motion with or against a non-conservative force and you had to add "work". Put in friction and you had to add heat as a type of "energy". The history of mechanics has been one of creating new kinds of "energy" in order to keep "conservation of energy" true.
  8. Jan 16, 2008 #7


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    that's because your last name isn't Bogdanov or Bogdanoff and you do not host a French pop-physics (or pseudo-physics) television show. if you were thus qualified, Halls, you would know what that means. :rolleyes:
  9. Jan 17, 2008 #8

    Andy Resnick

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    To be fair, the OP did ask a question central to physics.

    Energy is a property of objects and systems of objects. There are various forms of energy (e.g. mechanical, thermodynamic, informational), and they can interconvert from one form to another. We know some properties of energy- the total amount is conserved in a closed system, we can interconvert one form of energy to another in controlled experimental conditions, and we can quantify how much energy a particular object/system has.

    As for what energy 'is', you could just as easily as "What is 'red'? The fact that a simple answer doesn;t exist does not make the concept any less useful.
  10. Jan 17, 2008 #9
    Yes, absolutely!

    Actually, we have several such bookkeeping devices, like momentum, angular momentum, mass (in nonrelativistic case) etc.

    Actually, I am not sure that number of such devices is finite. Because some nonlinear equations have INFINITE number of independent integrals of motion. The first three of them are usually associated with mass, momentum and energy of the system. The rest of them are terra incognito.
  11. Jan 17, 2008 #10


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    Mmm, I thought that it did make grammatical (if not semantical) sense, and is, as such, a qualified, syntactically correct Bogdanov statement.

    "Is Energy something tangible or is Energy only apparent when certain base characteristics belonging to the topological composition of our universe interact or you may have another idea in mind which can play out in the real world?"

    is, as far as I understand, a question phrase composed of 3 sub-statements on the same level:
    "Is Energy something tangible"


    "is Energy only apparent when certain base characteristics belonging to the topological composition of our universe interact"


    "you may have another idea in mind which can play out in the real world?"

    although what is strange is that the last statement is an intonation question, while the other two are questions with inversion.

    Let's look at:

    "is Energy only apparent when certain base characteristics belonging to the topological composition of our universe interact"

    which is, I would think, a correctly formulated Bogdanov phrase.

    It has a main clause:
    "is energy only apparent"

    and a sub-clause (of time, or of condition, with "when"):
    "when certain base characteristics belonging to the topological composition of our universe interact"

    subject: "certain base characteristics, belonging to..."

    verb: "interact"

    It are hence the characteristics that have to interact.
    Which characteristics ?
    Those belonging to the topological composition of our universe.

    It is at the time, or on the condition of those characteristics interacting, that energy is apparent, and only then.

  12. Jan 17, 2008 #11


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    Can mental energy be considered here? chemical, and electrical, reactions in the head can sometime be extreme to the point of feeling exausted, both mental and physical.
    I sometimes get a flood of thoughts that continue for days, every waking hour, and then i seem to sort of shut down, i'll spend time doing things that seem to require very little thought or attention. This cycle repeats on a somewhat regular basis.
  13. Jan 17, 2008 #12


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    This is not an issue in "mechanics", and so it is not relevant here.

  14. Jan 17, 2008 #13
    I disagree with your assessment on my usage of the word topology. Mathematically the standard model, can be incorporated into a topology that can describe simple things like atoms. This is apparent because when protons, neutrons and electrons are combined, the elements that emerge are recognized for what they are, due to the combinatorial process, which is well known. Therefore to say that our universe can be described by a topology, even if it is complex in nature is closer to the truth, than you have been willing to admit.
  15. Jan 17, 2008 #14
    The fact that Energy in significant units does quantify an ability to do work, does not in any way, negate the quest for knowledge concerning what is it that causes this ability to perform work to be manifest. Mere numbers will not cut the cloth so to speak. Perhaps you will move towards the definitive technical term - force!

    On another note, although I accept the definition that energy is no more, no less, an ability to perform work and can subsequently be summarized by a mere number, I submit my hesitation in regarding this as an epistemological coup d'etat.
  16. Jan 17, 2008 #15
    There might well be some validity to what you're trying to say, but I think the problem is that you're using words in a way that raises some suspicion that you might have a less than complete understanding of them.

    I've never heard anyone who does research in this area say "the standard model can be incorporated into a topology", much less "the universe can be described by a topology."

    Spacetime, Lie Groups - yes. The SM or the entire universe - sounds iffy to me.
  17. Jan 17, 2008 #16
    This is precisely what I am after, your suggestion that the current understanding of energy is less than precise, in light of the new Quantum Mechanics.

    This definition of Energy as an ability to perform work can be dated back to Newton, if I am not mistaken, and it seems as if the current trend to walk the physics line without real epistemological support needs its proper attention.

    Additionally, I have not claimed as yet anything, that suggests energy consists of some "stuff" as you so eloquently stated it. I have asked for current mental notions which support the nature of Energy, while I have stated my own notion about how I believe energy shows up in our universe. It was stated clearly, but I repeat for effect, apparent when certain base characteristics (belonging to the topological composition) of our universe interact. Some of those base characteristics are summerized by the standard model, including spin and charge.
  18. Jan 17, 2008 #17
    How's this, then: "Energy is that quantity that is conserved as a result of the invariance of Physics under time translation."? (see Noether's Theorem) :smile:
  19. Jan 17, 2008 #18
    We can predict measurements of energy, and our measurements agree well with those predictions. What deeper epistemological support is needed in Physics?

    I think the earlier post about defining "red" is quite apt. We could go around in epistemological circles for a long time, trying to decide on how we know what "red" really is, but at the end of the day, I don't think we'll be any more able to find the red car in the parking lot.
  20. Jan 17, 2008 #19
    Nice thing that mechanics!

    One topological basis of our world would consist of things like spin, electric charge, heat, and gravitational states, while another more basic one, would have quark compositions.

    How does these interact with each other making it look as if energy exists! or even as things-in-themselves? Do you think that a black hole is a thing-in-itself?
  21. Jan 17, 2008 #20
    Hmm, to summarize, interesting thought that one, if not a downright fascinating notion! :smile: :smile:

    p.s. could this be symmetry breaking?
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