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I What Came First the Magnet or the Field?

  1. May 9, 2017 #1
    Below I paraphrase David Tong from:

    David Tong -- What is Quantum Field Theory? You can find this by googling.

    1. "According to our best laws of physics the fundamental building blocks of nature are fields."

    2." Every particle in the universe ... is a tiny ripple of the underlying field"

    According to basic school physics if we move the magnet we move the field. But it seems that according to QFT it's sort of the other way round and to move the magnet we must move the field. The only way I can think of moving the field is by moving something else, for example moving a second magnet. It's a bit chicken and egg.

    So is the field more fundamental than the particles of the magnet? Or, perhaps, should particles and fields share equal dominance as being considered as fundamental?
     
  2. jcsd
  3. May 9, 2017 #2

    Vanadium 50

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    How on earth did you get that?
     
  4. May 9, 2017 #3

    I got it from the article I referred to where it was stated that fields (not particles) are the "fundamental building blocks of nature".. One way I see of interpreting that is to assume that to make changes to the particles you need to make changes to the fields. But traditionally it's the other way round which is to make changes to the fields you need to make changes to the particles eg move the magnet. I imagine particles and fields as being interlinked as a particle/field construct and I can't see why one aspect of that construct, namely the field aspect should be considered as being more fundamental than the other aspect.

    Sorry I tried to include a link but it didn't work.
     
  5. May 9, 2017 #4

    atyy

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    In QFT, the magnet is also made from fields.
     
  6. May 9, 2017 #5
    And particles.
     
  7. May 9, 2017 #6

    atyy

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    Particles are excitations of fields.
     
  8. May 9, 2017 #7
    the 'magnet' and the 'magnetic field' are different things, so they are described with different fields.
     
  9. May 9, 2017 #8
    Changes in fields can cause changes in particles.
    Changes in particles can cause changes in fields.
    What came first?
     
  10. May 9, 2017 #9
    Not sure about the point being made. What of the two different fields describes the magnetic field?
     
  11. May 9, 2017 #10
    two fields do not describe the magnetic field. the magnetic field is ONE field, the magnetic field. however, with your taking about a magnet and a magnetic field: particles are electron* and photon, fields are electron and electromagnetic respectively.

    *for example
     
  12. May 9, 2017 #11
    no that's a sloppy description of what's going on, particles are excitations of a quantum field.
     
  13. May 9, 2017 #12
    It was you who suggested that the magnetic field is described by a field (post 7). That was unclear but now you've cleared it up. But I still don't see the relevance of your comments.
     
  14. May 9, 2017 #13
    when you move the magnet what particles are you moving?
     
  15. May 9, 2017 #14
    I'm not disagreeing that particles can be described as excitations of the field. I quoted David Tongs description of a particle in post one and I did not dispute atyy's definition, which is worded in the same way as yours in post six. So to make it clear I am not disputing anything about QFT. In fact I don't know enough about it yet to be able to do that.
    What I am questioning is the assumption that fields are more fundamental than particles. And I am doing that by reference to changes. So why is my reference to changes in post 8 an example of sloppy thinking? Please take another look at post one.
     
  16. May 9, 2017 #15
    I do not mean sloppy thinking, just a sloppy description in an academic sense, i.e. not very pedantic or precise. I'm saying that when these things are more clear and defined, the chicken and egg problem goes away in my view.
     
  17. May 9, 2017 #16
    To a large extent that depends on the system within which the magnet is moved.
     
  18. May 9, 2017 #17
    I'm asking you what particles the 'magnet', e.g. an iron bar magnet, is made of? its electrons, which are not excitations of the magnetic field, but they do 'cause' the magnetic field in some physical sense.
     
  19. May 9, 2017 #18
    I think we both know the answer to that but what's the point of the question?
     
  20. May 9, 2017 #19
    Will be back here later on.
     
  21. May 9, 2017 #20
    You can move the magnet by means other than the magnetic field maybe? A magnet contains charges, which although in motion, might perhaps be moved by an electric field?
     
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