250 — Of flying frogs and levitrons

Berry & Geim (10.1088/0143-0807/18/4/012)

Read on 27 April 2018
#Levitron  #physics  #levitation  #gravity  #Ig-Nobel  #frog 

Water is diamegnetic, which means that it is very slightly repelled by a magnetic field. This is true even of highly distilled water, which has virtually no in-solution ion content to speak of. There is a really good illustrative video here that explains this phenomenon further. In summary, a small rare-earth magnet is powerful enough to move a floating vial of water across the surface of a larger bowl of water.

That’s a pretty non-trivial amount of force generated non-destructively using only a static magnet! What amount of force is required to move something heavier… say… a frog?

Frogs are mostly water. (So are people, but much much less-so.) Is it possible to levitate a frog using only a magnetic field?

YES. And you only need about 16 Teslas to do it. That’s still a lot, by the way: For context, you’ve never experienced or probably ever even come close to 16 Teslas before; a rare-earth magnet is around 1T, and some of the most powerful MRI machines in use at hospitals are still only 9T. But 16T is not outrageous.

Berry & Geim did just this in the solenoid bore of a Levitron, and the achievement won them an Ig Nobel Prize, awarded to “achievements that first make people laugh, and then make them think.”

The frog, by the way, was perfectly unharmed by this levitation (though probably very confused).

In 2009, this work was repeated on mice (also seemingly in perfect health after the fact), bringing us one step closer to anti-gravity machines for humans — or artificial gravity for use in space.

Geim, incidentally, won the Nobel Prize for physics in 2010 for the invention of graphene. This was, as far as I can tell, entirely unrelated work.