Re; levitron

Ernest N. Prabhakar (
Mon, 7 Apr 1997 11:27:10 -0700 (PDT)

Ah, very nice. Of course, , this is going to ruin my reputation if
people actually start asking me PHYSICS questions, which I am actually
supposed to know something about. I do much better with management
and computer questions, where I know nothing. Which is why I want to work
for Apple marketing, where I'd fit rgt in. :-)

Actually, it is pretty clever. I think Iigured it out pretty quickly, but
I'll explain my logic. Anti-gravity does not exist (according t sme pretty
basic assumptions). They say they use permanent magnets, which happen to be
the only way to have sustained repulsion. So, one way to get levitation is
to sustain a big north pole over another north pole.

Unfortunately, every north pole has as south pole (yes, there probably are
monopoles, but they're awfully rare, like honest politicians and clueful
Mac owners:). Because of this, the sout pol wantst ge together with the north pole (rather homophobic, these poles).

The result, as anyone who's ever tried balancing two bar magnets on to o
other, is instabilit The slightest tipping, and the north pole goes up,the southpole goes down, and whammo, you're back in contact instead of floating free.

So, how to solve this? Gyroscopy! Because of a very cool use of intertia,
(which took an awful long time to prove in freshman physics, and I'm still
not sure I undesrtand it, but it really does work), gyroscopes always point the
same way. Thus, they keep the north end pointing down and the south up,
maintaining the levitation.

A very clever use of magnetism and gyroscopy. Magnetic repulsion is very
unstable, which is why levitating trains can be tricky. I suspect their
may be gyroscopes in such planned trains for precisely that reason. That is
why some trains are designed using monorail underhangs with magnetic -attraction-, which is more stable, but les fail-safe.

Nice find. Rohit, you now know what to get me for my birthday.
Also a good metaphor for the balancing act involved in shipping

-- Dr. Ernie, Physicist at large