Twospoons
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Odd behaviour of Neodymium magnet
So there I was, idly tossing a 30mm diameter neodymium magnet with one hand when I noticed an odd thing. The magnet refused to flip in mid air. If I
imparted a light flipping momentum the magnet would get about halfway through the flip, then reverse its motion mid air and come back down same side
up. If I started the flip with the opposite pole facing up, then the thing would spin madly in the air. Weird. Then I tried tossing it flat,
upwards, no spin. One pole up it would stay flat, other pole up it would flip over!
Would not have believed it if I hadn't seen it. But when you stop and think about it the reason is obvious - what I have in this magnet is a rather
strong compass (confirmed by suspension on a string) and what the magnet was trying to do was align with the geomagnetic field, which slopes downwards
at about 40 degrees where I live.
It doesn't work with harddrive magnets, as the poles aren't arranged right. The mag I was using was 30mm round, 5mm thick, with the circular faces
being the two poles. And very, very strong.
Try it - its a seriously odd thing to see.
Helicopter: "helico" -> spiral, "pter" -> with wings
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Mr. Wizard
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You have just discovered that the universe is a monopole magnet, and now you have to buy a black suit to get your Nobel Prize. Seriously though, it
sounds interesting. I thought about buying a couple of those spherical super magnets to see if they would interact while spinning with the poles in
the same direction. I'll have to get some now. How about a video to show us. I agree with your compass explaination.
Have you tried dropping the spherical magnets through a non magnetic conducting tube? Even the flat ones take forever to slide down an aluminum
surface.
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Elawr
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Wow... that is fascinating. I have totally GOT to get myself some super - magnets to play with. I'm trying to think how you could confirm
geomagnetism as the basis for your magnet's nonballistic behavior. If you could determine the exact vector of the earth's field at your locale... I
think that if your magnet axis of rotation be made parallel to the geomagnetic - then there would be no influence and the magnet would spin like any
nonmagnetic disk. If spin axis perpendicular, then effect should be maximal.
This is conjecture only by a nonphysicist, a hunch in other words. Try and see - I'd love to hear whathappens!
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12AX7
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I've got some tabular magnets, pulls from hard drives (dang, I chipped the chrome plating on breaking them from the magnet assemblies). I've also got
access to a bar of silver. Very interesting observation there, as regards eddy currents. 
Tim
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Twospoons
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I'll see if I can video it. It would make an interesting post to youtube.
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woelen
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Also very funny is keeping a NdFe-magnet locked up in the field of a coil, through which a few 100's of mA are running. Wind some wire around a test
tube (preferrably a thin one) and put in a rod-shaped NdFe-magnet. You can launch magnets with such setup, but you can also lock them up in the field,
floating in the air. When they want to move upwards, then they are drawn back, if they want to move downwards, they are drawn up.
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12AX7
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They're also trapped (by torsion) in the tube, though.
Tim
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Twospoons
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Had to try the eddy current drag thingy. With the same magnet I used before, and a piece of right angle aluminium extrusion 35x35x2mm thick, it took
5 seconds  to fall 1 metre, vertically. Impressive!
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12AX7
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A whole meter? Takes that long to fall across the bar of silver I had...truely, an impressively conductive piece of metal  Heavy
copper and aluminum do pretty well too, though. You'll get even better results with 1/4 and 1/2" plate.
Tim
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Twospoons
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I tried the 1/2" plate. 3sec to fall 0.5m, so definitely much slower. Wish I'd tried this when we had all that 1/4" copper busbar ....
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franklyn
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The induced field's eddy current wastes away as heat that is why the magnet
progressively slips, the colder the substrate the longer it takes. If the material
is superconducting then the magnet should remain suspended indefinitely.
I seen this done:
Remove the cover from an old Hard drive, and power it up to spin the disks.
( the 5 1/2 inch size gives you bigger disks to work on ) You can then levitate
a strong magnet above the spinning disks due to the eddy field generated.
Not exactly the same , but it's similar to the superconducting Meissner effect.
( It occurs to me now this could serve the purpose for that floating bed post
of a while back , by hiding a spinning turntable beneath just under the flooring )
http://www.sciencemadness.org/talk/viewthread.php?tid=6400
A similar effect can be made with any conductive matter ( it need not be ferrous )
using a stationary coil to produce a high frequency strong alternating field.
http://blog.modernmechanix.com/2006/03/20/look-its-flying-di...
( scroll to the bottom there are two pages to view click the thumbnail pics )
This is essentially the same as the hardware for induction heating, the only
difference is the strength of the field with regard to the weight of the matter
acted on. http://www.sciencemadness.org/talk/viewthread.php?tid=3626
Update
I was surprised to realize the geomagnetic field in the U.S. is around 60˚ from
horizontal until you realize the approximate location of magnetic north is Hudsons
Bay Canada which is just next door.
These USGS maps illustrate the expected inclination at various latitudes around
the world. ( also called dip and slope , not to be confused with declination which
is the offset of magnetic North from true geographic north )
http://geomag.usgs.gov/charts/IGRF2000.inc.pdf
This next one is quite large and downloads slowly ( Red lines indicate inclination )
http://geomag.usgs.gov/charts/ig00i.pdf
There is concern that the field strength is diminishing at about 1% every ten years
and may reverse sometime. Without a terrestrial magnetic field to deflect cosmic
rays this could have deliterious consequences for living things worldwide.
[Edited on 18-12-2006 by franklyn]
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