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Is energy really 'another' entity?

  1. Jan 29, 2006 #1
    Okay, this may sound weird, but here is a very basic question...

    Why is energy considered 'another' entity than matter when its dictionary meaning is simply "the capacity of matter to do work"? It seems to be just a property of matter. Moreover, we cannot experience energy through our senses in any form, we can only experience its effect on matter. We do not see light energy but only the object that reflect the light entering our eyes. We do not hear sound energy but only the vibrating effect produced by it. Also we never experience heat energy but only heat. Energy in no way interacts with our senses directly but is still considered something other than matter. I realize some reasons for it, but cannot really completely understand.

    Thanks!

    -Vayne
     
  2. jcsd
  3. Jan 29, 2006 #2

    ZapperZ

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    But using your logic, why would matter even "matter"? All you care about is what you "sense". So why not say matter is nothing more than what your senses are triggering in your cortex? So you and I don't have to exist. All the effects that you need are what you are perceiving.

    I have a feeling this thing will eventually end up in the philosophy forum.....

    Zz.
     
  4. Jan 29, 2006 #3
    "So why not say matter is nothing more than what your senses are triggering in your cortex?"

    Yes, this is what seems to be coming out of the whole discussion. Every-time physicists discuss this at quantum level, they have a feeling that matter should not exist in the first place, but it does.
    But what I am talking about here is something different and most probably unanswered. On one hand it is said that annihilation of matter, results in gamma ray shower (that are massless). On the other hand it said that "energy is the capacity of matter do work". Both are contradictory because if the latter is only true then annihilation should not lead to total destruction of matter, but it does. And so it means that energy and matter are seperate "things", though however, energy is inherently packed in matter particles, but when it is not how can it affect matter? Or what does it even means something other than matter?
     
  5. Jan 30, 2006 #4
    question of existence

    As it has been said in this forum, you may end up with Philosophy forum. However, I wish Vanesh to consider the following point (maybe from Philosophy):
    If you say that the only thing that your senses percieve exist then it would mean that percetions you had in dreams are part of history. It is true that I <saw> myself killing the president of a nation in my dream. There is no doubt about my having percieved this. But next morning I woke up watching the person I killed in my dream as walking in live television broadcast. So my perception during dream has a diffrent kind of logic and must not be mixed up in the logic of my wake up state. This leads me to believing that my perception alone are not my guide to Truth. Perception may be deceptive.

    There is no doubt that definition of energy as it appears in the text books of physics is indeed tricky. Is it the property of matter to be affected by energy? But these days we talk of energy densities to be behaving like masses and that mass is a form of energy (relativity). So it follows that there is only one entity namely energy in the space-time.
    We have to realise that the problem of existence can not be solved by perception alone. For that matter I can not be sure of existence of myself. Or about the existence of the world arond me. That is why des cartes argued that, it may be true that (while he was woken up) I may be dreaming all the time. Or maybe that the world around me may not exist but its existence may be just an effect caused by a devil in my mind. However, it is true that I am <now> thinking all these things. So I am sure that I am thinking about the perception. This thinking must not be untru or this thinking can not be denied. And as I am sure tht I am thinking therefore I am sure of the existence of myself. If I dont exist then these thinking can not exist (in vacuum). So existence of myself is certain. Cogito ergo sum.
    When I am awake my obervation of the world around me has a certain logic and a certain mathmatics. When I dream sometimes 2+2 is not 4. So as there is a certain logic in the behaviour of objects around me, I belive that they have a property of existence. My perception is corroborated by the perception of the others as they communicate to me. As far as I am concerned it is my definition of existence. I know that this is incomplete. But this is how I knowthat science works.

    I hope I did not bore you much. I wish someone could make supplements to my comment and give a better description to what makes a thing to exist in sence of physics.
     
  6. Jan 30, 2006 #5

    ZapperZ

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    Come again?

    Physicists very seldom discuss such a thing. Philosphers, maybe since this is very much right up their alley. But physicists really do not have time for such things. Besides, we're never paid to talk about such things. And please cite for me the popular opinion among physicists that "matter should not exist in the first place". Remember, in my post, I was applying YOUR LOGIC from your post.

    But you are stuck with a less general conservation law. You think there is only a "conservation of energy" and another for "conservation of mass". Einstein has shown that there is a MORE GENERAL conservation law, the conservation of mass AND energy, since one can be converted to another. There is nothing inconsistent about anhilation of matter-antimatter into photons because of this.

    Furthermore, you need to be VERY careful on how you look at the definition of "energy", and to not confuse what we use in intro physics text as THE standard definition. The ability to do with is valid, but it is a simplistic definition since "work" isn't necessary F.dr all the time (eg. atomic transition).

    All you need to do is look at the Lagrangian/Hamiltonian mechanics, to see that we DEPEND on the energy dynamics in our description of the universe. The "Schrodinger equation" is one such form. To trivialize energy as simply something that can we replaced would require you to account for why it is THAT important and the starting point for all of our view of the world.

    Zz.
     
  7. Jan 30, 2006 #6

    vanesch

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    Ok, although the rest is highly philosophical, I feel called to respond here...

    Brrr, funny what people read in what I write! Two days ago I was reading "Philosophy for dummies", and it struck me that what I wanted to say, is in fact close to what Plato said - he said it in a much better way, btw, a clever guy, that Plato :redface:, with his "men in a cave" story.

    Just for the record: I was FIGHTING the idea that all we ever have to consider is what our senses perceive (which is the positivist viewpoint), and tried to make the point that the rumors of death of the hypothesis of a real, objective world which is described by physical theories are a bit premature, but that on the other hand, it could be that what we perceive is only indirectly related to what is "really out there". Dreams and so on being an example, but it could also be that being awake suffers from that property. I'm only taking that POV because it makes it easier for me to visualise the formalism of quantum theory, that's all. Not because I'm on crack.

    The viewpoint I have on the issue is that there is a mathematical structure that is the perfect description of nature (call it, the perfect laws of physics). In how much our current theories come close to that structure, I don't know, but the best we can do is to assume they are a good approximation. What we perceive is some kind of destillate from that perfect structure. This is VERY, VERY Plato-like, in fact.

    So "what" is supposed to be out there ? Consider it, according to the theory you're using, to be the mathematical structure of the theory. In Newton's mechanics, there are "matter points" in an Euclidean space, with numbers (mass, charge...) attached to it, as a function of a parameter, which we call "time".
    In classical field theory, it are vector (and other) fields on a 4-d manifold: sections of the cotangent bundle of spacetime and some dynamical prescription.
    In quantum theory, it is the ray in Hilbert space, constructed using whatever degrees of freedom we think there should be (field modes, particles, strings, wobbles, beables...) and a unitary operator standing for "time evolution" or something of the kind which gives us the dynamics.

    In what way these things "are really out there" is of course purely a matter of metaphysical speculation, but my point is, was, and will be, that as long as we can do that, that it is a good idea to do so, because it devellops intuition of "how nature behaves" and hence how one should crank the handles of the theory under study.

    What is "energy" ? Well, it is a quantity that is derived from (part of) the structure, and that quantity has a lot of interesting properties, as related to the structure. Often, it is a conserved quantity. Often, it is related to a symmetry, called "time translation invariance". As such, "energy" is not really "materially there". It's a NUMBER that we calculate from the "state of the world", or from the "state of a piece of the world - the system under study".

    Amen.

    yes.
     
  8. Jan 30, 2006 #7
    How has noone brought up the string theoretics, unless I am mistaken and it has already been stated, that all of matter and voids alike are composed of energy of different frequency?
     
  9. Jan 31, 2006 #8

    ZapperZ

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    Because it has not been verified and accepted. It's bad enough trying to explain this using conventional physics. This thread will not produce anything meaningful if we include speculative and still-developing stuff.

    Zz.
     
  10. Jan 31, 2006 #9

    ahrkron

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    To get back to the original question,

    It is not considered another entity.

    I think the main point to stress here is that "energy" is a name for a number that we have learned how to calculate in many types of systems, and which can be used to predict a system's behavior.

    It is *not* a "substance" hidden behind matter, or anything like that.

    What happens is that matter behaves according to certain rules, and those rules imply that certain numerical combinations of lengths, speeds, etc. will have a constant result.

    This, in turn, comes from a more basic mathematical fact: when, in a set of rules (of certain type) you have a symmetry, there will be a conserved quantity (you may want to google for "Noether's theorem").

    In particular, energy conservation comes from the fact that the laws of physics are the same no matter when in time you look at the universe (i.e., they are symmetric under time-translation).
     
  11. Jan 31, 2006 #10

    Q_Goest

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    Kinetic and potential energy can only be calculated or measured in reference to another location in space or coordinate system, and then only indirectly. The kinetic energy of a bullet for example, typically infers the bullet's kinetic energy with respect to the gun that shot it, but the kinetic energy a bullet has must be compared to something else just as potential energy must be compared to something or somewhere else.

    Gamma rays or electromagnetic radiation however seem different in that it is not measured in relation to some other coordinate system. Is that correct? That seems to imply it exists independantly and not simply in relation to something else.

    These two 'types' of energy seem different in how we view them.
     
  12. Jan 31, 2006 #11

    ZapperZ

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    You are forgetting that EM radiation can have their wavelength or frequency shifted due to relativistic Doppler effect. So two people in different inertial frames will measure different photon energies.

    Zz.
     
  13. Jan 31, 2006 #12

    Q_Goest

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    Yes, good point. So is the conclusion that energy must always be measured with respect to something else, or can energy ever exist without such a reference?

    Ex: A photon doesn't have mass so we have a massless particle which has energy even though the amount of energy must be measured with respect to some other reference. I suppose if we were moving along at light speed, we could say the photon has no energy either with respect to us, but then it has no energy and no mass.
     
  14. Jan 31, 2006 #13

    G01

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    I think I agree with what you say here but, (since this thread is somewhat philosophical), energy is just a conserved quantity like you are saying. It doesn't have to be an actual "substance" inside a particle in order to make it move.

    But then again, if energy is just a mathmatical quantity that describes a state of a system that we have observed, isn't mass the same thing?
    Mass is a number, which we define, that quanitfies an objects resistance to acceleration, or reaction to gravity. Mass need not be some "stuff" inside matter. Its just a quantity that describes our observation of something, as is energy.

    Matter and energy, creations of the human mind..........Wow, blows your mind huh??
     
  15. Jan 31, 2006 #14
    But in the context of this subject, if any form of sciences would be apt to explain the gap in common knowledge, I would assume that the developing theory of physical existance being composed of energy forms would fill the void in our known theoretics. Though, I do appreciate a response that does take into account that at some point if it does come into fruition, then string theory would cause many energy based enigmatic subjects to be redefined.
     
  16. Jan 31, 2006 #15
    Matter and energy are not creations of the mind; they are what make the existence of the human mind and the tools with which we perceive them possible.
    The problem with definitions is they do not necessary logically
    relate the concepts they pertain to to the perceptual level which is a requirement for an objective understanding.
    I am no physicist but isn't energy basically the agent of change in a cause and effect relationship between two or more objects (whether through direct contact or remotely), or an effective property of the object itself? Can photons be other than messengers between objects unless they combine to form objects themselves?
    (zz, please note that I phrased these as ?s. :confused: I have no desire to redefine physics terms at this time.
     
  17. Feb 1, 2006 #16
    Amazing! :)

    My internet connection was down for two days and now I see the topic isn't really very bad hehe. I thank everyone for their inputs.

    Well, I knew the kind of reactions that I would be getting on this topic and I know it seems to be a very childish question at first sight, but now let me get into detail and explain why I started this thread.

    First of all, let me inform you that I now almost completely understand the answer to my question. By means of studying some popular works again (I study them but I tend to forget them because I am no physicist by profession), I seem to be finally coming to the conclusion that energy is actually another entity. For example, take the simple example of an electron in an atom observing a photon. When an electron observes a photon or what is also known as "packet of energy", it jumps to a higher state. Now look at this picture closely - the electron observed "packet of energy" and jumped up, it has been affected by energy and so the direct conclusion is that energy is something 'other'.

    Even though we do not have conclusive proofs that energy is the ultimate building "block", but some recent theories (such as string theory) and observations seem to be pointing towards that. Honestly speaking, I did not like the string theory much until I watched a special program on it on the Discovery channel, and it seems to be very promising.

    But if matter is made up of energy, then energy is supposed to be the only entity? My view on this issue is that what makes the two of them distinct is the fact that energy is imperceptible but matter is not. Maybe energy is infinitesimally small to be viewed or maybe it exists in another dimension than those we can perceive, I am not sure about that as nobody is.

    So the deduction is that energy does exists independent of matter, but it is beyond our sensory capabilities. Now, I said, I "almost" understood this issue because we still haven't found out (or perhaps I am unaware) exactly how and when does energy sums up to become matter - I think we do not have any mathematical treatment for that yet.

    Now I come to the dream issue. To make it clear, I was talking about senses and not mind. Dreams do not come through your senses but through your mind and that too when you are sleeping, and so it is not the perception of the real world.

    Let me now answer all the talks about this thread going to the Philosophical section. If it has been said as a matter of fact then it is fine, because it for the Admins of this forum to decide. But if it is sarcastic comment thinking this topic to be unimportant, then I must say that this issue is indeed very important, because all these discussions, experiments and observations are eventually based on consciousness and consciousness is based on our senses, and so it is very important to know the limits to our senses.

    P.S. Those who do not agree with me (on views of energy being another entity or even this topic being important), they should refer to the book by Paul Davies called Other Worlds. It is a very exciting book and should be read with imaginations flying high. By that I mean, do not close your mind on any possibility, even if the idea is coming from a non-professional like me. :smile:
     
  18. Feb 1, 2006 #17

    ZapperZ

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    This is actually not correct.

    A electron cannot absorb a photon. That violates several conservation laws.

    What you had in mind (because this mistake occurs very often and most of us know exactly what you are trying to describe) is the atomic TRANSITION when a photon is absorbed. But this isn't done by the electron. It is done BY THE WHOLE ATOM. The excited state is reflected by the promotion of an electron to a higher energy state. But this isn't something "absorbed" by the electron. An electron, by itself, has no "energy state" like that when it is confined to an atom.

    So what is excited and what is doing the absorption is the atom, not the electron.

    Please keep in mind that these popular science shows can only describe things superficially. String theory is horribly complicated, beyond what you can imagine, and it suffers from the severe lack of experimental verifications, after all these years and the unbelievable amount of hype. So I wouldn't call it "promising".

    Similar to "wave particle duality" that seems to be of such importance to many non-physicists, I also find it rather puzzling why it is of such importance here to make a distinction between these two. In many areas of physics, such as high-energy physics, there are no distinction between "energy" and "mass", so much so that it is a standard to simply quote mass and energy in units of "eV" (high energy physicists tends to use c=h=1). In physics, one needs to show that making a distinction between different things under whatever circumstances does make a difference, and not just simply a matter of tastes or personal preferences. It DOES matter if a particle is a boson or a fermion. It DOES matter if something is a lepton or a hardon. Going from one to the other changes a lot of the physics. But wave-particle in QM? Energy-mass in elementary particle?

    The difference may be semantic, and it may matter at the elementary level. We teach intro physics and tell students of conservation of energy and conservation of mass as two separate things. If this is the "level" you are asking for, and this is all you want, then we can go with that and say they are different. But if you want to transgress beyond this and go for ALL that we know, then you need to know that at some point, such distinction becomes a non-issue. It isn't what makes physics publications, unless one is discussing the Higgs.

    Zz.
     
  19. Feb 1, 2006 #18
    Okay, I take your words on this, but as much as I saw the show, the explanations seem to be good in the beginning, although I know it gets very complicated later on.

    In this regard, let me ask you, what is it that you (as of now) consider the ultimate building block of Nature? Others can join and post their views.

    Thanks!
     
  20. Feb 1, 2006 #19

    ZapperZ

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    I don't understand what you define as "ultimate building block of Nature". There are something that are known as "fundamental particles". But as vanesch can testify, I and many other physicists (even a few Nobel Laureates) in condensed matter would argue that these "fundamental" particles may in fact be themselves "emergent" properties. What is "fundamental" now, isn't going to be later. And knowing everything at the fundamental level doesn't tell you anything about the complexity and emergent behavior.

    So why does this matter so much?

    Zz.
     
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