PFE006: Levitation

I found out this morning that the Nobel prize in physics was awarded to a pair of Russian physicists, Andre Geim and Konstantin Novoselov for their work on graphene (pdf) in 2004 which also happens to be my area of research. What is interesting about this duo is that Konstantin was only 30 when he did the relevant work.

But more interesting than that is Andre Geim's other notable award: the Ig Nobel Prize. The Ig Nobel prize is awarded for work done in a field that can't and/or probably shouldn't be repeated, but still carries certain merit. Andre's claim here was that in 2000 he levitated a frog

in a magnetic field. "But people have levitated lots of stuff before, including trains!" you cry out, and rightly so. But trains are made of metal, frogs aren't. Geim was demonstrating levitation for all of us to see, essentially doing what I am doing.

How does this work? Well you place a frog in a tub in a strong magnetic field... yep. Magnets again. Crap.

Not to worry. The relevant physics here comes from the fact that the frog is mostly water. It turns out that water is rather diamagnetic (there are metals that are much more so, but I haven't found any bismuth frogs hopping around after a rainy day). Diamagnetic is a big word, but isn't actually all that scary. Remember how one magnet could be brought near a paper clip and the paper clip temporarily acted like a magnet and was attracted to it? The paper clips are what we call paramagnetic (the original magnet that got all this started, like those on your fridge, are called ferromagnetic). Paramagnets are attracted to nearby magnets while diamagnets are repelled. The actual behavior at the atomic level that describes the difference is definitely out of the scope of this post. But suffice it to say that a diamagnet in the shape of a frog, in a strong enough magnetic field can float.

That's levitation.