I had a really difficult time deciding what to post about concerning my latest read, Electricity and Magnetism by Edward M. Purcell. I took enough notes to post entries for a month at least! What I’ve decided to do, however, is to postpone other topics (especially on the nature of the electron) for other books I plan to read, and today just vent about my perplexity when it comes to understanding the source of magnetism.
Apparently, there are three sources (that are ultimately one source) for Magnetism….
1) a traveling charge, 2) a negative charge revolving around a positive center, and 3) a negative charge rotating on its own axis [no positive center].
The first source of magnetism would be represented by the typical electric Current; the second by imagined Electrons revolving around the purported Nucleus of an Atom; and the third by a “spinning” Electron. All three sources can be viewed ultimately as one source: a moving charge.
[Aside: there are claims that rotating or revolving “positive” charges can also generate magnetism, and that the nucleus of an atom exhibits such magnetism, but as I am not convinced that charge actually comes in two flavors, I will not delve into that. I will say, however, that Nuclear Magnetic Resonance is a real phenomenon, in the sense that strong magnetic fields do impact biological molecules or atoms (apparently only in the very short-term) in measurable ways that can be, and are, used to good effect during medical examinations]
Scientists tell us that the magnetism generated by an electric current is due to the moving charges which make-up the current. And that pretty much is the full “explanation.” The next-level question… Well, why do moving charges create magnetism?... doesn’t seem to have ever been well-answered.
In the case of natural magnets, scientists tell of us that these consist of atoms containing tiny charged particles moving in circular motions, and that the movement of these particles results, more or less, in little coils of electric current. Thus, the magnetic effects found in naturally magnetic substances are also associated with moving charges. In fact, moving charges are the ONLY known cause of magnetism.
Similarly, the magnetism of the Earth is credited to the circular movement of charged particles around the Earth’s core.
As far as individual atoms go, there are two sources of moving charge: 1) electron rotation or “spin”, and 2) electron revolution.
Apparently, electrons rotating or spinning on their little axes counts as a “moving charge”– even if the electron were to sit and spin in one place. One problem with this view is that many theoretical physicists tell us that it is silly to think of an electron as actually having a physical spin or rotation… The label “spin” is just a way of speaking about some mysterious characteristic of the electron which allows two electrons to occupy what would otherwise be the same location inside an atom– an impossibility without the “spin” characteristic– whatever spin is in a physical sense.
The second supposed source of atomic magnetism stems from the moving charge created by the revolution of electrons around the positively charged nucleus purported to be at the heart of every atom. But there’s a similar problem with this view… The notion of tiny localized spheres of negative “charge” called electrons has long been superseded in other areas of physics by the idea that the electric charge surrounding an atom is more like a “cloud” or a “wave” or even a “probability distribution” than like actual little spheres revolving and rotating like planets in a miniature version of the solar system. This solar-system model of the atom has, in fact, long been considered quaint by physicists.
So, although scientists give us “explanations” of magnetism, in actuality their reasoning is quite suspect and inadequate.
In the case of magnetism caused by an electric current, we still don’t really know WHY a moving charge should cause magnetic effects– we don’t even really understand what a “charge” is. And with the idea of the Ether long ago discarded, the transmission of magnetism through space is still quite mysterious. Basically, physicists have had to bring back a version of the Ether, either in the form of a conductive “Space-Time” or in the proposal that the vacuum of Space can– miraculously– produce “virtual” particles and effects.
And when it comes to atomic-level magnetism, we have to close one eye and ignore how the rest of physics today views the atom.
Furthermore, when we look around at the real world, we find that most things do NOT possess noticeable magnetic properties. How is this to be explained with all the electrons out there revolving and rotating? Scientists have come up with two explanations…
The first one, I actually find completely reasonable within the frame-work of generally accepted beliefs concerning magnetism… Explaining the absence of atomic magnetism stemming from electron revolution, physicists say that atoms in a substance face every-which-a-way, and that thus their magnetisms generated by electron orbits cancel each other out [although I’ve always been a little confused as to how these magnetic energies “cancel-out” each other in a Universe in which no Energy just disappears]. It is rather the exception then the rule when a particular substance possesses atoms that happen to line-up in the same direction.
Sometimes an object can possess numerous “domains” of similarly oriented atoms, but then each of these domains tend to face different directions, and thus they too cancel each other out, with the same net result of non-magnetism in most substances. Of course, when the domains DO line up, you have something which WILL exhibit magnetic properties. And this magnetism can even be permanent for those cases in which, once lined-up, it would take more energy for the domains to move out of alignment than to just stay the way they are.
The second excuse for the dearth of magnetism in the world, I find less plausible… Explaining the absence of atomic magnetism stemming from electron rotation or “spin,” physicists say that most electrons do their “spinning” next to a buddy-electron which is spinning in exactly the opposite direction, with the result that their magnetic effects are cancelled-out one by the other. It is only in the exceptional case of a material possessing several unpaired electrons that rotational magnetism is exerted to a noticeable degree. But even for those cases in which there are unpaired electrons, their spins often still do not line up because of “thermal agitation”– atoms are always jostling about, keeping electron spins from lining up.