Why do positive and negative charges attract?

  • #51
At the risk of once again being overly simplistic and stupid, I'm going to suggest a very simple way of explaining the attraction and repulsion of particles. Particles spin. Ta-da!

Like spinning tops, particles spinning in the same direction will violently repel each other, and particles spinning in opposite directions will be drawn together.

Now everybody feel free to point out why this explanation is incorrect. I have found that I can actually learn quite a bit by coming up with a simple way of visualizing something, and then having people much smarter than me tell me why I'm completely wrong. So feel free to point out my error.

Why can't a simple thing like spin, explain the attraction and repulsion of particles?
 
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  • #52
Fiziqs, you are getting dipole moments this way, while charge is a monopole.
The difference is that while monopoles attract/repel with force proportional to 1/r^2 and it doesn't depend on their orientation ... monopole-dipole (like spin-orbit) interaction is 1/r^3, dipole-dipole 1/r^4 (e.g. making ortho-postronium much more stable than para) and they depend on relative orientation.
 
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  • #53
jarekd said:
Fiziqs, you are getting dipole moments this way, while charge is a monopole.
The difference is that while monopoles attract/repel with force proportional to 1/r^2 and it doesn't depend on their orientation ... monopole-dipole (like spin-orbit) interaction is 1/r^3, dipole-dipole 1/r^4 (e.g. making ortho-postronium much more stable than para) and they depend on relative orientation.
Ok, after taking some time read up on the terms in this post I must admit that it is still going over my head. Is there any way to dumb this down? I realize that the post is probably self explanatory to most people here, but unfortunately I'm a little slow.

For example, I'm not sure what you mean when you state that charge is a monopole, or even what dipole moments are really.

Any clarification would be helpful, thanks.
 
  • #54
  • #55
I have often pondered what charge is and how is it able to exert force. The best I could come up with is that charge is some sort of wave function spin or precession. I can't ever remember all the members of the standard model but it seems to me that every particle of matter is either charged or formed of sub-particles that are charged while anything that moves at c is not charged. This is probably not a coincidence. Matter particles or sub-particles seem to be waves structured in such as way as to cancel propagation (string theory?). They move at c but 'run on the spot'. Any precession creates stress or charge with the sign depending on the direction. Attraction or repulsion can then be viewed as a tendency mitigate stress.

All the above comes with a ceveat. I only dreamt it up to stop myself going stark raving mad! I do not claim any of it as valid science. I would welcome comments from people who know QM to clarify the issues raised here and to point to some good papers to read ...
 
  • #56
Trenton, as I have tried to explain above - spin and charge are quite different. The former emphasizes some axis (of spin), while pure charge doesn't - is spherically symmetric.
Spinning vortex can be intuition for spin, like Abrikosov vortices in superconductor - carrying quant of magnetic field (spin of particle is also related with magnetic field).
However, for charge we need a different type of topological singularity - not 2D (like vortex), but 3D, like hedgehog. For example we have a field of unit vectors and positive charge is: all vectors outside, negative: all inside.
It is generally called topological index/Conley index: you take a sphere of some dimension, focus on the field only on this sphere and ask how many time it "wraps around it" - so called winding number.
Taking a circle in 2D you get fluxon or spin this way. Taking sphere in 3D you get point singularities - charges this way. It is how it is made in topological soliton models, like Faber's.
 
  • #57
Jarekd you are right. A 3D entity such as the hedgehog is required for charge. I googled hedgehog topology. I almost wished I hadn't but only almost. It is a far better model.

Does all this mean though, that all charged particles are indeed EM waves or photons which by means not altogether clear, have become hedgehogs and are radially rather than linearly oscillating - and that this obstructed action (in that the whole no longer propagates at c) is responsible for the charge?

I shall read up your other stuff on the strong/weak interactions and the Higgs but this might take me some time. It seems to me though, that both the strong and weak forces are really the laws of math and are not as fundamental as they are claimed. Hedgehogs appear to like the company of other hedgehogs even if they are the same sex as is proved by the high energy difference between atomc and mollecular hydrogen (covalent electrons). Siamese hedgehogs or particular multi-hedgehog configurations, perhaps forming a single albeit more complex soliton entity, have a lower energy level. In the nucleus where the energy levels are much higher a mix of the sexes is required to smothe the way but the principle is the same. Nobody has ever called covalence a fundamental force as far as I know so why attribute the quark configurations to one?

As for Higgs, is it really true that this long lost boson is the reason why all other particles have mass or is that just the BBC correspondents talking twaddle again? Einstein's GR describes gravity very much better than the BBC and a soliton hedgehog wave would neatly explain inertia - moving the hedgehog would automatically deform space since otherwise part of the wave would go superluminal and the other part subluminal.

It is nice we now have found the Higgs but do we really need it?
 
  • #58
'Why' is not philosophical here. There is a very, very real why! It could be as literal as the nucleus of a particle being slightly distorted to favor a specific direction of acceleration when it was spun, like a hammer throw and the magnetic field lines are just a characteristic of spin. It could be as abstract as a relativistic effect cause by the dilation of time and the resulting probability vector distortion. The reason why is deeply nested in the nature of matter and space/time as well, I think, in the nature of wave motion in the interstices of matter. If you heat a magnet enough it stops being magnetic which might imply that it is a product of the motion in the range of infrared wavelengths, which would be the electrons with a DeBroglie wavelength matching that frequency. The reasons will become clear as did other things, with time and people asking why. The wave nature of matter is the answer to most questions if we look deep enough. Tesla thought that, Schrodinger though that, and so did Planck. Even Einstein came around. Maxwells Equations give a good what and where but the why is mathematically being discovered to be more of a question than one might realize. If probability governs the motion of celestial bodies... then can't intention alter probability on a micro and macroscale? These are not sterile philosophical conjectures, these are mathematical directions of study!
 
  • #59
Trenton said:
Jarekd you are right. A 3D entity such as the hedgehog is required for charge. I googled hedgehog topology. I almost wished I hadn't but only almost. It is a far better model.
One of places they use this kind of topological singularities are liquid crystals, which can have thermodynamical tendency to form 2D sheets, 1D tubes or 0D hedgehog-like e.g. micelles.
In field theories it is a bit similar (but also different: wave-like instead of diffusion-like) - assume a field which has energetic tendency to locally break symmetry, like choosing a direction.
These directions can form e.g. hedgehog configuration, or generally any singularity of integer topological charge ... or maybe also more complicated topological structures - corresponding to further particles.
Does all this mean though, that all charged particles are indeed EM waves or photons which by means not altogether clear, have become hedgehogs and are radially rather than linearly oscillating - and that this obstructed action (in that the whole no longer propagates at c) is responsible for the charge?
From topological point of view, being charged particle means being hedgehog-like configuration.
Photon is a different story - it does not have charge, but it has angular momentum - it is kind of twist-like wave, like behind marine propeller.
I shall read up your other stuff on the strong/weak interactions and the Higgs but this might take me some time. It seems to me though, that both the strong and weak forces are really the laws of math and are not as fundamental as they are claimed. Hedgehogs appear to like the company of other hedgehogs even if they are the same sex as is proved by the high energy difference between atomc and mollecular hydrogen (covalent electrons). Siamese hedgehogs or particular multi-hedgehog configurations, perhaps forming a single albeit more complex soliton entity, have a lower energy level. In the nucleus where the energy levels are much higher a mix of the sexes is required to smothe the way but the principle is the same. Nobody has ever called covalence a fundamental force as far as I know so why attribute the quark configurations to one?
I don't like the idea of seeing particles as just abstract objects out of the field, while every charge is singularity of electric field - I believe we should search for concrete models for structure of fields near/inside particles.
There are probably different models possible, but we should always have in mind the successes of the Standard model - that while constructing Feynman diagrams for scenarios on these solitons, we should finally get constants in agreement with the current models.
As for Higgs, is it really true that this long lost boson is the reason why all other particles have mass or is that just the BBC correspondents talking twaddle again? Einstein's GR describes gravity very much better than the BBC and a soliton hedgehog wave would neatly explain inertia - moving the hedgehog would automatically deform space since otherwise part of the wave would go superluminal and the other part subluminal.
Soliton particle models also need Higgs-like potential: to handle the situation in the center of singularity, we have to get out of this potential - giving particle rest energy/mass.
But I don't know if it requires/implies a special corresponding "Higgs particle" - which in fact is just one of thousands metastable states.
 
  • #60
Why questions imply mechanics - the underlying mechanics of the level to which the why question is applied... but the suitable form of the answer for the why question is going to be another level of mechanics. At some level the answers tend to shift from mechanics to math - "why?" questions will ultimately lead all the way down to the fundamental axioms.

A simple attraction dynamics example is gravity. A possible answer to why things attract gravitationally (inverse square and mass relation) could be a geometric answer:

If a four dimensional space in rotation causes a universal three dimensional hyperbolic expansion with positive time, this is the same as if everything was getting larger, and the apparent mechanical result would be that everything seemed to be attracting each other. This expansion would be conveniently unmeasurable because the measuring devices would also be expanding.
This attraction would not require any mediating force and appear to be instantaneous (Newtonian) - because the apparent attraction would be only a geometric mechanical effect of the universal expansion.

You could say that might be the reason, but it can't be proved, so it is exactly as saying, "It just is". But if you want to know why the universe might be a rotating four dimensional entity, that is another why question...
 
  • #61
If they didn't, there would be no existence. Atoms could't form. There would be no light. Subhan Allah wa bihamdihi
 
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  • #62
While it's meaningless to ask "why" on a fundamental concept, the truth is that we don't know what concepts are fundamental, and what we call fundamental physics gets more esoteric as we learn more. In the case of charges attracting and repelling; I think it's possible to answer that in terms of the stationary action principle. And the stationary action principle can be explained in terms of a Feynman path integral formulation. Beyond that, I don't think there are any good answers.

The problem that Feynman was talking about in the explanation is that the stationary action principle formulation isn't any more intuitive than just stating that charges repel. So you are answering one mystery with another. The more fundamental explanation is better because it matches experiment more precisely, but that doesn't mean it is any more understandable or satisfying to a questioning mind. When you ask why, you probably are searching for something more understandable, not something that gives more precise experimental results. But nothing is understandable below a certain level.
 
  • #63
For the moment, there is not a clear why but we can consider this behavior of charges as a "principle" of physics, and it will remain so until a better, unifying principle integrates many of the present "principles".
 
  • #64
Great arguments: we can't understand it just because we cannot ... the same as for quantum mechanics ...
Maybe just try changing attitude for a moment and really search for an answer ...

Do we have in mathematics something allowing only constructions of integer "number"?
Yes we have - so called topological singularities and we call this number as winding number or Conley index or ... topological charge.
So what would be dynamics of such topological solitons? Let us look at simple 2D field configuration for "-" and "+" singularities in different distances:
https://dl.dropboxusercontent.com/u/12405967/fig1_cr.jpg
the first observation is that the closer they are, the weaker stress of the field - down to zero when they finally annihilate.
Practically any field theory we would define here, its spatial derivatives correspond to stress of the field - fields have tendency to minimize energy, what means here that opposite charges attract.

And we are very close to Faber's model of electron, where due to using natural Lagrangian, such 3D analogues get dynamics described by Maxwell's equations ...
 
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