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    • CommentAuthorjoshs
    • CommentTimeMar 11th 2010
     
    Posted By: Grimer
    Posted By: Angus
    Posted By: GrimerIt will have to be the fishes, then.


    I loaves to have to ask what you mean.

    I am surprised you didn't attempt to answer the question as to why strain energy is signed, i.e. we can readily distinguish between positive (tensile) and negative (compressive) strain energy and yet kinetic energy is unsigned.

    After all, just as with kinetic energy we have (-v)(-v) and (+v)(+v), so also with strain energy we have (-ε)(-ε) and (+ε)(+ε). Yet in one case we distinguish between positive and negative energy and in the other case we don't.
    Did you lose the distinction between forces which are vectors and energy which is not when you lost your mind, Frank?
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    For some, humanity has lost a lot on its way to enlightenment.
    Unfortunate.
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      CommentAuthorGrimer
    • CommentTimeMar 11th 2010 edited
     
    Posted By: alsetalokin
    For example, potential and kinetic energy are the positive and negative compliments you seek, Frank. You can't do with just kinetic.
    http://www.youtube.com/watch?v=ZIW3AHocPXI

    In my view that is not the answer - but thanks for giving the matter some thought and being constructive.

    Nice video. Is that you in the cockpit?
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      CommentAuthorAngus
    • CommentTimeMar 11th 2010
     
    Posted By: Grimeram surprised you didn't attempt to answer the question as to why strain energy is signed, i.e. we can readily distinguish between positive (tensile) and negative (compressive) strain energy and yet kinetic energy is unsigned.


    Al has said it. I'll try with a metaphor.

    Energy is not a vector. It is a scalar. It is convenient to assign negative values to some manifestations, but this does not imply that the energy involved is different in any way from other energy. For example - gravitational potential energy is generally considered as a negative quantity. This is because it is convenient to consider it zero when the gravitating bodies are infinitely distant. Reduction from zero gets you a negative potential energy at distances closer than infinity. As the bodies get closer, the potential energy is reduced, and the kinetic energy increased (assuming free fall).

    It's all just accounting. Energy is like money. What you earn you consider to have positive value. What you borrow you consider to have negative value. But it is all the same entity.

    You seem to be differentiating two different kinds of energy according to the directions of force or velocity vectors. As I have tried to point out with humour, this is ridiculous. Directions are eliminated in the computation of mechanical energy. If you were somehow to define an energy-like measure that retained the directions of force or velocity vectors, then these would still be vectors - you would not just get two types of energy. You would have to specify direction. And this new measure would have nothing to do with, say chemical energy.
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      CommentAuthorGrimer
    • CommentTimeMar 11th 2010
     
    Posted By: Angus
    Posted By: Grimeram surprised you didn't attempt to answer the question as to why strain energy is signed, i.e. we can readily distinguish between positive (tensile) and negative (compressive) strain energy and yet kinetic energy is unsigned.


    Al has said it. I'll try with a metaphor.

    Energy is not a vector. It is a scalar. It is convenient to assign negative values to some manifestations, but this does not imply that the energy involved is different in any way from other energy. For example - gravitational potential energy is generally considered as a negative quantity. This is because it is convenient to consider it zero when the gravitating bodies are infinitely distant. Reduction from zero gets you a negative potential energy at distances closer than infinity. As the bodies get closer, the potential energy is reduced, and the kinetic energy increased (assuming free fall).

    It's all just accounting. Energy is like money. What you earn you consider to have positive value. What you borrow you consider to have negative value. But it is all the same entity.

    You seem to be differentiating two different kinds of energy according to the directions of force or velocity vectors. As I have tried to point out with humour, this is ridiculous. Directions are eliminated in the computation of mechanical energy. If you were somehow to define an energy-like measure that retained the directions of force or velocity vectors, then these would still be vectors - you would not just get two types of energy. You would have to specify direction. And this new measure would have nothing to do with, say chemical energy.

    Sorry Angus. Being in the black and or in the red may be the same to you but it sure ain't the same to me. Ectropy is not the same as Entropy.
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      CommentAuthorAngus
    • CommentTimeMar 11th 2010 edited
     
    Well I was talking about your "Ekergy". Entropy is also a scalar. How do you define your "Ektropy", mathematically? Do not dare to suggest that a definition is up to me.
    • CommentAuthorjoshs
    • CommentTimeMar 11th 2010
     
    Posted By: AngusWell I was talking about your "Ekergy". Entropy is also a scalar. How do you define your "Ektropy", mathematically? Do not dare to suggest that a definition is up to me.
    Frank's either having you on or he's been sniffing a lot of powerful solvents for a long, long time.
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      CommentAuthorGrimer
    • CommentTimeMar 11th 2010
     
    How do you define tensile and compressive strain energies mathematically? They are both scalars but they are not the same. And now I have to dash off to another appointment,
    • CommentAuthorjoshs
    • CommentTimeMar 11th 2010
     
    Posted By: GrimerHow do you define tensile and compressive strain energies mathematically? They are both scalars period but they are not the same. Irrelevant segue struck. And now I have to dash off to another appointment,
    You cannot be so fucking dense that you think that just because two things have some characteristics that are different that you therefore redefine the measures of what they have in common. By such fuck wit reasoning mechanical energy must have a vector direction compared to electrical energy.
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      CommentAuthorQuanten
    • CommentTimeMar 11th 2010
     
    Posted By: AngusWell I was talking about your "Ekergy". Entropy is also a scalar. How do you define your "Ektropy", mathematically? Do not dare to suggest that a definition is up to me.


    Ectropy is minus entropy. That is, he give it another name because it is negative.

    Except a passing mention in thermodynamic cursus, I never heard of it used.
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      CommentAuthorDuracell
    • CommentTimeMar 11th 2010
     
    Just don't get him started on accounting - I don't want to have to read all about debit and credit journal entities in the context of ekergy / energy and ectropy / entropy!
    • CommentAuthorJonR
    • CommentTimeMar 11th 2010
     
    joshs - are you suggesting that someone else deserves to be FOTW?
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      CommentAuthorAngus
    • CommentTimeMar 11th 2010
     
    Posted By: Quanten
    Posted By: AngusWell I was talking about your "Ekergy". Entropy is also a scalar. How do you define your "Ektropy", mathematically? Do not dare to suggest that a definition is up to me.


    Ectropy is minus entropy. That is, he give it another name because it is negative.

    Except a passing mention in thermodynamic cursus, I never heard of it used.


    Well, it could be called "information". Same equation, negative sign. I shudder to think what the woo flingers will make of that.
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      CommentAuthorAngus
    • CommentTimeMar 11th 2010
     
    Posted By: GrimerHow do you define tensile and compressive strain energies mathematically? They are both scalars but they are not the same. And now I have to dash off to another appointment,


    Nice escape. The question was how YOU defined "EKTROPY".

    I am no longer able to suppress the belief that you are having us all on.
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      CommentAuthorGrimer
    • CommentTimeMar 11th 2010 edited
     
    Posted By: Angus
    Posted By: GrimerHow do you define tensile and compressive strain energies mathematically? They are both scalars but they are not the same. And now I have to dash off to another appointment,


    Nice escape. The question was how YOU defined "ECTROPY".

    Ectropy
    From Wikipedia, the free encyclopedia
    In thermodynamics, ectropy is a measure of the tendency of a dynamical system to do useful work and grow more organized.[1] Ectropy, in a loose sense, can be thought of as the opposite of entropy. Ectropy is minus entropy. That is, instead of saying "lose entropy" you can say "gain ectropy", instead of saying "gain entropy" you can say "lose ectropy".
    The term was introduced in the late 20th century by mathematician and philosopher Willard Van Orman Quine and is often more intuitive than its counterpart. The term's merit is that in order to understand a concept, it can be useful to look at it from the other side. Sloppily speaking, ectropy signifies order; slightly more exactly, usable energy. Actually, what we call energy is often ectropy.
    The Earth, for example, gets electromagnetic waves from the sun and sends electromagnetic waves back into space, but the incoming waves have shorter wavelengths (higher frequencies) and therefore more ectropy. So the Earth's ectropy is increased by the sun. When we eat, we take in ectropy from the food.
    The Second Law of Thermodynamics says that in a closed system, ectropy will decrease. An organism which is isolated from the outside world will die and deteriorate because its ectropy decreases. It needs ectropy coming from the environment to keep living.
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      CommentAuthorAngus
    • CommentTimeMar 11th 2010 edited
     
    For Pete's sake! This is just the negative of entropy, which somebody has given a new name. What's your actual point? There is no honest purpose in giving a different name to the negative of the same thermodynamic scalar.

    FYI the negative of entropy is used in information theory (did you get Shannon's book yet ?) and is called Negentropy, and would be described by the same equation as entropy, but with a minus sign, as I just pointed out. Every EE learns about it before the end of second year. It is a measure of order rather than disorder. So what?

    I am ever more convinced that all this stuff from you is nothing but trolling.
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      CommentAuthorGrimer
    • CommentTimeMar 11th 2010
     
    You might as well say Good is just Negevil.White is just Negblack, etc.
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      CommentAuthorDuracell
    • CommentTimeMar 11th 2010
     
    Posted By: GrimerYou might as well say Good is just Negevil.White is just Negblack, etc.


    Yeah - I agree - For example it is much better to call faiths such as Christianity etc. "religions" instead of "neglogics" or "negreasons"! ;)
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      CommentAuthorGrimer
    • CommentTimeMar 11th 2010 edited
     
    Posted By: Angus ...
    There is no honest purpose in giving a different name to the negative of the same thermodynamic scalar.
    ...

    Are you suggesting that Quine was being dishonest - that he was trolling the academic community?
    • CommentAuthorbc
    • CommentTimeMar 11th 2010
     
    Posted By: GrimerAre you suggesting that Quine was being dishonest - that he was trolling the academic community?
    The Wikipedia entry is nonsense so I wouldn't be surprised. "When we eat, we take in ectropy from the food" is wrong on many levels.

    Philosophers especially seem to like to create BS terms for ordinary things, often imprecisely defined mathematically. It doesn't make the concepts less vague or more real though.