# How do magnetic fields work?

How do magnets affect one another? For instance, if you place two bar magnets in a hard vaccum, will they attract/repel each other, and if so, how is the magnetic force transmitted? (by wave, particle, whatever…)
Also, what is responsible for the magnetic field of the sun?
-Oli

Until somebody comes along who knows what they are taliking about, read this:

http://www.straightdope.com/mailbag/mlightwaveparticle.html

It will at least give you some background info on Electromagnatism before any specific discussion begins… Great read!

Physicists, please correct me if I’m wrong here, but I believe the following are true:

1. A static magnetic field is produced by one or more moving charges. These charges are moving at a (more or less) constant speed.

2. A changing magnetic field can be produced two ways: a) By moving charges, wherein their speed is changing, b) A changing electric field. The latter is how a magnetic field is sustained in an electromagnetic field (e.g. radio wave).

Coorect. In addition, static magnetic fields are also produced by unpaired or unbalanced electron spin, as in ferromagnetic materials. BTW, I believe the magnetic field produced by a moving charge is actually produced by its electric field (which is changing at each point).

So for the OP, vacuum has nothing to do with it. AFAIK (and that’s not very far), the electromagnetic force is moderated by photons, but I’m not sure exactly how magnetic fields propagate in the latest theories.

1. Two bar magnets will attract/repel each in a hard vacuum.

2. The magnetic force is one aspect of the electromagnetic force. See the Straight Dope article linked previously by kevsnydefor more info.

3. From this website:

Here’s another website about the Sun’s magnetic field:
http://solar.physics.montana.edu/YPOP/Spotlight/Magnetic/

And from the master:

http://www.straightdope.com/classics/a3_339.html

However, one of the questions in the OP hasn’t really been answered…
as one of the fundamental forces of the universe, how does magnetism propagate in a vacuum?
Gravity is regarded as curving space-
does magnetism do something similar,
or is it ‘moderated by photons’,
or what?
What is this action at a distance lark all about, eh?

Channeling Chronos

As summoned, I arrive… But I’m not sure what else to add. Magnetic fields are one component (or three components, or six, depending on how you count) of the electromagnetic field, and in fact, Special Relativity requires that both exist and be aspects of the same thing. Electromagnetic fields don’t need a medium, and they can be described in terms of virtual (or even real) photons. I will not attempt to go into more detail on how virtual photons give you a field.

As for explanations of the fundamental forces, a relativist will tell you that gravity is perfectly well-understood as curvature of spacetime, but it’s a mystery how the other forces fit in. A particle physicist will tell you that electromagnetism and the nuclear forces are well-understood in terms of virtual force vector bosons, but that it’s a mystery how gravity fits in. It depends on what you’re looking for as an “explanation”.

Thank you, now I know what to look for
(in order to be baffled).