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Is there a simple explanation to how photons interactions cause the effects of magnetism. Always wondered what magnetic fields actually are. I came across the idea when looking at the EM waves of light.

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    $\begingroup$ This may seem like a route to deeper understanding, but it is really kind of a dead end. Photons are defined, roughly, as the fundamental excitations of the electromagnetic field, so this is really asking "are magnetic fields some sort of excitation in the electromagnetic field?" And the answer is yes, but it is almost circular reasoning. I am brushing past some details involving how we keep track of radiating electromagnetic fields versus non-radiating ones (which are sometimes described as due to "virtual photons"), but in my opinion that distinction does not change this fundamental issue. $\endgroup$ – Rococo Jun 20 '17 at 22:50
  • $\begingroup$ I believe this may be what you need. $\endgroup$ – Cort Ammon Jun 20 '17 at 22:51
  • $\begingroup$ @CortAmmon wasn't much talk about how photons come in to play but thank you, was a interesting video. Are electric fields also photons then? $\endgroup$ – Aaron Jun 20 '17 at 23:05
  • $\begingroup$ No, there is no simple explanation on electric and magnetic fields or photons. But electric and magnetic fields are linked. They are part of the same phenomenon we call the electromagnetic field. A specific excitation of this field of a certain energy level that propagates through space at speed c we call a photon. $\endgroup$ – Brad S Jun 21 '17 at 12:50
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I came across the idea when looking at the EM waves of light.

Light is a classical concept completely described by solutions of the classical Maxwell equations. . There are no photons in classical physics. Just electric and magnetic fields in a sinusoidal time and space dependence .

Photons are elementary particles in the standard model of particlce physics. In the quantum mechanical framework photons are the exchange boson of first order electromagnetic interactions, and there exists a mathematical framework, quantum field theory, where creation and annihilation operators acting on a photon field will describe electromagnetic interactions, including electric and magnetic fields. The mathematics is not simple.

To get an intuition of how classical light waves can emerge from photons have a look at this link.

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Always wondered what magnetic fields actually are.

There are two possibilities to induce magnetic fields.

The first is the alignment of the magnetic dipoole moments of subatomic particles - mostly electrons - inside a solid. Some materials are permanent magnets and some materials could be magnetized by an external magnetic field. In contrast to an electric field, where charges are separated, for the induction of a magnetic field the magnetic dipole moments of subatomic particles will be aligned.

The second is the emission of photons. However one produce electromagnetic radiation - in a light bulb through chaotic acceleration of the involved electrons or in an antenna rod by the common acceleration of electrons forth and back the rod - in all cases the emission has an electric field component and a magnetic field component. For an antenna rod the magnetic field component is aligned perpendicular to the rod:

enter image description here

The animated sketch see on Wikipedia.

What is the effect of mgnetism?

The effect is simple that an existing magnetic field can induce a magnetic field in materials.

The nature of the constituents of magnetic fields - as well as of electric fields - is not considered. One simply satisfied with the macroscopic effects. This led to the situation that the interaction between magnetic fields and between electric field are explained by virtual photons and this is a useless explanation because beside this claim there is no use or explanation how virtual photons are working.

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