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Do we know what energy is ?

  1. Sep 8, 2008 #1
    Do we know what energy "is"?

    Hi everyone,

    According to what I have read a string is a minute amount of vibrating energy. Is the word "energy" here used as an approximate for the lay reader?

    I was led to this thought because if the vibration of strings make up matter and energy then what's the difference between the "macro energy" produced by vibration and the "pure" non vibrating energy?

    Basically I'm asking, what is energy?

    Thanks!
     
  2. jcsd
  3. Sep 8, 2008 #2
    Re: Do we know what energy "is"?

    Energy is the potential to do work.
     
  4. Sep 9, 2008 #3
    Re: Do we know what energy "is"?

    That doesn't really answer what energy is though just what it does.

    I can't imagine a string of "potential to do work"
     
  5. Sep 9, 2008 #4
    Re: Do we know what energy "is"?

    Energy is the sum of a calculation, not a tangible thing.

    k
     
  6. Sep 9, 2008 #5
    Re: Do we know what energy "is"?

    Thats what I used to think, but don't they say that a photon is a packet of energy?

    And like I said before how can an intangible thing take the form of a string?
     
  7. Sep 9, 2008 #6

    russ_watters

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    Re: Do we know what energy "is"?

    A photon has energy. It isn't energy itself. Energy is not a "thing". You're looking for a deeper meaning where none is necessary.
     
  8. Sep 9, 2008 #7

    vanesch

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    Re: Do we know what energy "is"?

    It doesn't. All this is figurative talk. As Russ said, you can eventually say that a string HAS energy (or momentum or mass, or whatever other quantifiable property). The only thing that IS energy is a quantity in a calculation.

    To give you an analogy: is a bank "interest rate" ?
     
  9. Sep 9, 2008 #8

    jtbell

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    Re: Do we know what energy "is"?

    Better: Is a bank money?
     
  10. Sep 9, 2008 #9

    vanesch

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    Re: Do we know what energy "is"?

    I was going to say that first, but money also has a tangible representation (paper money, or gold bars, or...), so this was not sufficiently abstract...
     
  11. Sep 9, 2008 #10
    Re: Do we know what energy "is"?

    hahaha, thats what I used to think until I started reading about string theory and QM which confused me into thinking energy was physical.

    So now I have two other questions:

    If there is no such thing as pure energy then what is a string?

    And what was so revolutionary about E=mc^2 if E is not a real thing?

    Thanks again!
     
  12. Sep 9, 2008 #11

    russ_watters

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    Re: Do we know what energy "is"?

    E=mc^2 was revolutionary because no one had connected matter and energy in that way before.
     
  13. Sep 9, 2008 #12
    Re: Do we know what energy "is"?

    well when you think about it, energy is primarily mass. Mass is like frozen energy. It really makes you think, what exactly is energy. But when a string vibrates, it gets energy, energy converts into mass.
     
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