Multilayer magnetic shielding

I'm talking about really long range fields, up to intergalactic distances. They persist across billions of years, which electric fields do not.

The electric potential of the Earth is very nearly zero, because it's immersed in a conducting medium (the solar wind). The intergalactic medium is also (weakly) electrically conductive, because most of the gas there is ionized.

Not just rarity, apparent nonexistence. But we've all been beguiled by the particle physicists into thinking that prettiness matters, i.e. that reality must be this way and not that way, just because the equations are nicer-looking.

That works once in awhile--Maxwell's displacement current being the primary example--but it's rare.

They'd behave just like positive and negative particles. In any system, the force on any object is minus the gradient of the total energy with respect to its position. The B field has an associated energy density, so positive and negative monopoles would attract because that reduces the volume integral of |B|**2.

The nonexistence of stable magnetic monopoles is one of the best-established limits in physics, due to those intergalactic fields.

Cheers

Phil Hobbs

div B = 0

div E = rho (times a proportionality constant depending on your unit system).

In vacuo, rho = 0 and so the two are completely symmetrical.

If there were monopoles, it would be

div B = rho_M.

Cheers

Phil Hobbs

You're confusing the field, which is a real thing, with "lines of force", which are not. The B field pulls and pushes in an obvious fashion and has its own energy density.

There's no such thing as a gravitational field line. Masses are not monopoles because they don't have polarity.

Cheers

Phil Hobbs

On a sunny day (Sun, 21 Feb 2021 19:51:08 +0100) it happened Jeroen Belleman wrote in :

I was thinking about this, and it seems to me the 'magnetic effect' simply choses the way of least resistance. Yes, magnetism is something that moves, creating a magnet here will be detected much later (speed C) elsewhere

so you have, in your case

==================== metal

thing

=================== metal

the u0 of space versus that of the metal. The magnetic signal wil chose the lowest resistance path, the metal, similar to

---- 1 Ohm ---------- | | --- thing 1000 Ohm------------- | | ---- 1 Ohm-----------

less will flow in the 'thing' of 1000 Ohm if shorted by the 1 Ohm conductors.

But always there is the _flow_. There will probably a slow down of the movement of the magnetic (EM) field in the metal as it plays ping-pong-recreate between those atoms.

As to monopoles sure you could imagine something that only flows outwards, like a star shines.

Long ago I tried explaining universe from a flow POV, very interesting, 'fields' are just a static visualization (math). I got quite far, sort of fell asleep after that And I am not a physicks so for what it is worth :-) Same goes for graffiti eh gravity ? I like Le Sage's explanation, that involves moving particles, flow.

What do you make of that?

Yes. It's not called 'flux' for nothing.

Jeroen Belleman

Huh, I never thought of that... I always pictured G field lines going from one mass to another... but if there were lines, well the nearest mass is the source so the field line should just return to itself. Gravity is weird... I've also been reading too much of the Triton station blog. :^)

George H.

rofl, need to know your music to understand that one :-)...

A multipole gravity expansion would consider each massive particle to be a monopole.

Field lines keep the math correct for inverse-square-law central force, which certainly does work for gravity (unless one invokes general relativity). Field lines are just another abstraction. Forces are real, observable; fields are useful abstractions.

There aren't any field lines for electricity or magnetism either. A field has a direction and an intensity at each point in space, the same idea for any field, electrical, magnetic, gravitational or whatever, and may be visualized by lines or little arrows.

The picture of fields consisting of discrete lines that many people seem to entertain is wrong. I suppose the idea comes from the behaviour of iron filings in a magnetic field, which

Jeroen Belleman

The idea is also expressed in the right hand rule. Quote:

The right hand rule states that: to determine the direction of the magnetic force on a positive moving charge, point your right thumb in the direction of the velocity (v), your index finger in the direction of the magnetic field (B), and your middle finger will point in the direction of the the resulting magnetic force (F). Negative charges will be affected by a force in the opposite direction.

OK, you have finally convinced me. Your efforts have paid off. I can now visualize a magnetic field emanating from a point charge, the same as with electrons and protons.

But why are magnetic monopoles so rare? How would they be created?

In what metric, and under what gauge transformations? Do expound.

BS. The math is correct in any case--thinking about field line density is a mental crutch.

Field energy density is also observable.

Cheers

Phil Hobbs

How do we observe fields, except to infer them from forces on particles?

The field-lines picture fails for non-inverse-square-law fields, BUT if we imagine virtual particles mediating those fields, then a lifetime for a massive virtual particle makes field-lines that terminate... next mental step gets you to a Yukawa potential model, and voila! We have predicted the pion!

The Faraday effect, the Casimir effect, the Aharonov-Bohm effect....

That last one is especially interesting, because it shows that the magnetic vector potential is a real thing--it influences the phase shift between the arms of a quantum interferometer even if the field is completely shielded everywhere that the wave function has nonzero amplitude.

Cheers

Phil Hobbs

On a sunny day (Mon, 22 Feb 2021 17:40:36 +0100) it happened Jeroen Belleman wrote in :

And magnetic monopoles??

The Faraday effect is because of electron molecular orbitals perturbed by the magnetic field, and that means the B field did work on those electrons. Casimir effect is usually referred to as a force. As for Aharonov-Bohm; I get a headache considering that one, since it makes a phase shift without any obvious energy implications. Collisions DO make phase shifts, too (and transfer momentum), but that's not the same.

It's interesting, all right. Two-ibuprofen interesting.

whit3rd wrote in news:963a6da0-67e6-4065-99d2- snipped-for-privacy@googlegroups.com:

Only idiots take shit that perforates the stomach lining. And worse are those that take them multiple times a day and not over a meal.

Educate yourself and use a different mild strength pain reliever.

Don't be an idiot... or as much of one anyway.

Or hell, go ahead and eat them like candy. We need multiple ways to reduce the population and clean up the gene pool.

Yes. Shelkunoff was addressing shielding of EM fields (AC), not electrostatic or magnetostatic fields (DC).

Joe Gwinn

Power supply shielding is in the intermediate range--it's AC, so you don't need monopoles to absorb the B field, but it's way inside the near-field region.

Cheers

Phil Hobbs