Magnetic fields in vacuum

  • Thread starter Tonyo
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  • #26
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Saying that the field doesn't exist if there is nothing for it to act on is like saying a wall doesn't exits until you walk into it.
That's not entirely true.
Interaction with virtual particles are required for the existence of a magnetic field in a vacuum, or so the current theories suggest... to my understanding that is.

But, you are correct: A wall is a wall, is a wall.
A wall does NOT cease to exist if no observer or external force is absent.
 
  • #27
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Heh thanks Pallidin, I did understand your first post, I tired to pull some sarcasm of my own.. guess I failed lol... Anywho, it seems like we might finally be getting somewhere with this post!! my goodness.
I really don't know how to respond to your question, however I will make an attempt at it. Does the theoretical existence of virtual particles disturb my perfect vacuum...... possibly; yes, however, If we are correct in saying that this virtual particle interaction stuff is responsible for extending a magnetic field in vacuum, then if they don't really exist(virtual particles) then neither will the magnetic field. So Physicists had to create mathematically imaginary "stuff" which is not possible to detect measure or observe in any way in order to explain things that we CAN detect but are not capably of fully understanding.
So I will not ask about eliminating the virtual particles in a perfect vacuum to make a "super perfect vacuum" since their very mathematical existence is a form of explanation.

And yes Bob, We can make a field producing device and put it in a vacuum and turn it on, and know exactly what it's going to do. But now with QED as an explanation, we can turn it on without knowing what it will do, but be able to predict it and somewhat explain it's operation mechanism via QED theory, even if it's in a perfect vacuum.
 
  • #28
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Ahh Feldoh, thank you very much for this reference on the "Casimir effect". It's something I've never heard of before, but it seems to be a part of QED, more precisely aimed at this electromagnetic field business.
I shall thoroughly enjoy reading it in more details, Much thanks to you Sir.
 
  • #29
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A magnetic field can most certainly EXTEND into a vacuum. With or without any observer.
Agree
However, I have a question: Does your notion of a "perfect" vacuum include the idea of NO virtual particles? If that is so, you might be correct that it would not be possible for a magnetic field to extend into that environment.
Why are virtual particles required in order to have a magnetic field present?
But, here's the kicker... there is no known ability to create a vacuum that does not have virtual particles.
If there are no Coulomb fields, like electrons and nuclear Coulomb fields, can virtual particles be present? In most (all?) cases, strong Coulomb fields are required.

Keep in mind, Tonyo, that whereas virtual particles are speculated to be responsible for a number of phenomenon, including the extension of magnetism in vacuum space,
Oh really?
...............virtual particles have NEVER been shown to actually exist. Their very nature of existence excludes direct observation. They are INFERRED from reliable experimentation through mathematics.
Not true. Virtual particles, in the form of vacuum polarization, create very large measurable atomic level shifts in muonic and pionic atoms. These atomic level shifts are necessary to get agreement with other experimental measurements of muon and pion masses. I think the argument is whether an existence proof based on indirect measurements is the same as actual proof of existence. Nobody has actually seen gravity yet either, but it exists....

Bob S
 
  • #30
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Bob,

There is no current explanation of a magnetic force in a vacuum without the notion of virtual particle existence and interaction.
 
  • #31
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Magnetism is NOT a solely emissive force.
Currently, it is a "loop" phenomenon.
 
  • #32
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Bob,

There is no current explanation of a magnetic force in a vacuum without the notion of virtual particle existence and interaction.
Are we discussing magnetic forces or magnetic fields? The OP asked about whether magnetic fields could exist in a perfect vacuum. I associate a magnetic force (in this discussion) with the Lorentz v x B force, which does require a moving charged particle.

Bob S
 
  • #33
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Sorry, I meant fields.
 
  • #34
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Bob,

There is no current explanation of a magnetic [STRIKE]force[/STRIKE] field in a vacuum without the notion of virtual particle existence and interaction.
Aren't Maxwell's equations sufficient?

Bob S
 
  • #35
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Well, I quess that's where I get confused.
A magnetic field can extend into a vacuum. This is widely accepted, and I accept it.
But HOW does it do this?

Magnetism is not fully emissive like a photon, in the sense that a photon of light can be emitted and never return to it's source, yet magnetism currently requires a return to source. No "magnetic laser" so-to-speak can be constructed(at this time) without the discovery and manipulation of "monopoles"... if they exist.

This is all so confusing to me.

I am under the impression that the extension of a magnetic field in a vacuum requires the idea of "virtual particles" as a transport medium/assist, since magnetism is not fully emissive.

Again, I don't know. I could be spouting BS for all I know.
 
  • #36
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Well, I quess that's where I get confused.
A magnetic field can extend into a vacuum. This is widely accepted, and I accept it.
But HOW does it do this?
It just does...your question assumes that there's something special required for it to do so. Saying "virtual particles" doesn't answer the question, it just shifts it...how do those virtual particles move through empty space? Why are they emitted? Virtual particles serve to fit these fields into the mathematical framework of quantum mechanics and allow their behavior to be described in a systematic way, not to answer the question of why things work the way they do.


Magnetism is not fully emissive like a photon, in the sense that a photon of light can be emitted and never return to it's source, yet magnetism currently requires a return to source. No "magnetic laser" so-to-speak can be constructed(at this time) without the discovery and manipulation of "monopoles"... if they exist.
It has nothing to do with magnetism being emissive or not. Magnetism does not "return to its source"...field lines are described as closed loops, but this is a way of visualizing certain characteristics of the field, there's nothing actually traveling in loops away from and back to the magnet. Magnetic monopoles would be the magnetic equivalent of charged particles like electrons and positrons...these particles certainly exist, and don't have looped "field lines", but electrostatic fields aren't any more or less "emissive" than magnetic ones. There's no "electrical laser" either.

Really, it's foolish to try to treat them as separate forces...they are both aspects of electromagnetism. One may dominate in a given situation, but you can't have one without the other. Accelerate an electron and you see a magnetic component to the field. Accelerate a permanent magnet and you see an electrical component to the field. Do either of these and you will produce electromagnetic radiation, which always has both components.


I am under the impression that the extension of a magnetic field in a vacuum requires the idea of "virtual particles" as a transport medium/assist, since magnetism is not fully emissive.

Again, I don't know. I could be spouting BS for all I know.
Why would a wave packet be any more able to cross vacuum than a continuous field? Or why would the field be less able?

Virtual particles aren't a medium, they're a mechanism used to describe fields in the quantum mechanical description of things. Relativity is a field theory, and does not involve virtual particles in its description of the behavior of fields. Neither description is complete or final.
 
  • #37
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61
Well, I quess that's where I get confused.
A magnetic field can extend into a vacuum. This is widely accepted, and I accept it.
But HOW does it do this?

Magnetism is not fully emissive like a photon, in the sense that a photon of light can be emitted and never return to it's source, yet magnetism currently requires a return to source. No "magnetic laser" so-to-speak can be constructed(at this time) without the discovery and manipulation of "monopoles"... if they exist.

This is all so confusing to me.

I am under the impression that the extension of a magnetic field in a vacuum requires the idea of "virtual particles" as a transport medium/assist, since magnetism is not fully emissive.

Again, I don't know. I could be spouting BS for all I know.
I find it helpful to think of a magnetic field as an illusion created by the combination on an electric field and special relativity. Here's a link to an explanation of how that works...
http://physics.weber.edu/schroeder/mrr/MRRtalk.html

This isn't to say that electric fields are fundamental and magnetic fields are derived, it could just as well be the other way around, bu this is the way I have found it easy to think about.
 

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