[dkhar]

On the subject of interesting magnetic effects, a lot of people don't know that pretty much all matter is magnetic, just that the strength of the interaction is a lot smaller than what we're used to with ferromagnets.

All materials exhibit a diamagnetic (pushes against the field) effect, but in many materials, that effect is overwhelmed by a competing paramagnetic (pushes in the direction of the field) effect. Most of the things we call "magnets" exhibit ferromagnetism, which typically produces much stronger forces than either of the previous two.

H2O is particularly interesting, because it's actually diamagnetic, and will push away from magnetic fields. Given a strong enough magnet, you can have a lot of fun with this effect by putting common water-filled objects in its field: http://www.ru.nl/hfml/research/levitation/diamagnetic/

[snarfy]

Another fun fact: Magnetic fields are a consequence of relativity and length contraction of electric fields.

http://physics.weber.edu/schroeder/mrr/MRRtalk.html

This video also talks about it: https://www.youtube.com/watch?v=1TKSfAkWWN0

[agumonkey]

So a MF is just a twisted EF diffusion ?

/me on his way to watch that video

[hrjet]

Nitpick: relativity can explain magnetism, not cause magnetism.

[snarfy]

True, it explains them in terms of electric fields, but we still don't know what those are.

[readerrrr]

We know:

http://en.wikipedia.org/wiki/Electric_field

http://en.wikipedia.org/wiki/Electric_charge

http://en.wikipedia.org/wiki/Quantum_electrodynamics

An electric field is generated by electric charge and time-varying magnetic fields

Charge is the fundamental property of forms of matter that exhibit electrostatic attraction or repulsion in the presence of other matter. Electric charge is a characteristic property of many subatomic particles.

[danbruc]

Nitpicking again - the fields are a working mathematical description but, as far as I know, we don't know if or in what sense they are real things, whatever real thing even means. The electrical and magnetic fields change when you switch reference frames, so that does not sound like something that really exists independent of an observer. The vector potential on the other hand does not change but it does not seem real either because it has gauge symmetry.

[snarfy]

We know that the A field is more fundamental (at least Feynman thought so):

http://en.wikipedia.org/wiki/Aharonov%E2%80%93Bohm_effect

[mrfusion]

Interesting. Does it explain permanent magnets too?