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Maxwell's equations

  1. Apr 23, 2008 #1
    Are Maxwell's equations thought to be exact? I realize this question is very open-ended and loosely-phrased.
     
  2. jcsd
  3. Apr 23, 2008 #2
    Yes they are. But keep in mind that each one of maxwell's equations inevitably contains some sort of fundamental constant (mu or epsilon usually; not to mention electric charge etc etc) which are measured quantities and therein not exact.
    Does that answer your question?
     
  4. Apr 23, 2008 #3
    Yes.
     
  5. Apr 24, 2008 #4
    They're not exactly exact. QED makes slightly different predictions from classical electromagnetism.
     
  6. Apr 24, 2008 #5

    tgt

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    Mathematically, correct hence exact. Physically, it's a good approximation and only an approximation to model phenomena. Hence not exact physically. Is anything exact physically? No.
     
  7. Apr 24, 2008 #6

    rbj

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    lz, be careful.

    which constant in Maxwell's equation is measured and not defined (to an exact value)?
     
  8. Apr 24, 2008 #7
    Epsilon-not.

    Mu-not is defined. At least, that's what my professor said.
     
  9. Apr 24, 2008 #8

    rbj

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    you mean this epsilon-not ?
     
  10. Apr 25, 2008 #9

    Hootenanny

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  11. Apr 25, 2008 #10

    dst

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    I have one apple, I add another one, I have exactly two apples.
     
  12. Apr 25, 2008 #11
    Well, if you take into account the masses of the apples, which is what is physically relevant when you buy apples, then you have less mass when the two apples are together, right ? :biggrin:
     
  13. Apr 25, 2008 #12

    dst

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    Pfft, technicalities. If truth be told, the error is in disguise - it's either present in the definition(s) or as a constant in whatever expression you're using.

    On the other hand, there is no match for the physics of two cows™.

    You have two communist cows.
     
  14. Apr 25, 2008 #13

    robphy

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    by the way, that's
    epsilon-naught (epsilon-zero) and similarly for mu-naught.
     
  15. Apr 25, 2008 #14
    so, that applies, too, when two physicists get together?:wink:
     
  16. Apr 25, 2008 #15
    Umm--what? Are you using special relativity?
     
  17. Apr 25, 2008 #16
    I guess so :rofl:
    edit
    Actually, it depends. If they disagree on the status of "is string a theory ?", their interaction can be very exothermic.
    They have gravitational biding energy, don't they ?
     
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