i've got a magnet here a big fat
circular magnet it's a ring shaped
magnet rather like the sellotape so it
goes round this is a tiny little compass
needle so this
seems to be pointing upwards
and it moves
across it goes horizontal and then it
goes downwards out the other side so
there's a magnetic field coming out i've
got another little magnet this is again
a ring magnet on the top you can see
the magnetic field is pointing upwards
and on the bottom it's going
the other way
so now if i bring this downwards
there's a repulsion and you can feel as
you bring it down there's a repulsion
between these two
it's as though i have here a really big
magnet and what i want to do is place
this big magnet over the center and if i
get it over the center you can see it
will start to float
because of the repulsion between this
magnetic pole and the magnetic pole in
the base so as i lift this up it will
slide down
and it wants to stay about that height
this is a really strong magnet so it's
probably two inches or more above
so now what i want to do is get this to
be floating above there and i can't do
that normally because it wants to turn
that way
so i try and get it to go there and it
will fall down
so the trick is to spin it because if
you spin it it has a persistence it
wants to stay upright like a little
spinning top
so the object is to take this thing and
put it in a space above there spinning
round so it doesn't fall down and you do
that in two steps the first step is to
spin it on here you see how it wants to
repel against there
and of course i can go for half an hour
doing this take 57
take 972
until i get one that works and then i
lift it up bit by bit
to the point where it just
comes up and then it starts to float
in the air and if i got this level it
will stay there for a nice length of
time this is not held at home
i should have balanced it a bit better
and it's more or less level there
i can pass
a ring
through it
either direction
nothing is supporting you no magic is
involved no animals were killed and
there it floats
for about a minute and a half
and i don't know what to say that will
keep you amused for that length of time
it starts to precess when it slows down
because of the friction of the air
the rotation rate goes down a little bit
so here it's spinning around maybe at 25
rotations per second
and it slows down it slows down bit by
bit and you can feel after a while that
as it slows down the direction
it's pointing starts to waggle around a
little bit and then about 10 seconds
after that it plummets down to the
ground well this is the point where we
find out whether this is all a dream or
not it's just waggling so much that i'm
sure yes there it is
yeah it's a mixture of repulsion
and gyroscopic motion but the paper that
came out to explain it all was by sir
michael berry who is one of the leading
theoretical physicists of his generation
and he loves all these toys he would go
and analyze them in gory detail the the
idea of having a magnet
a rotating bag well no the spinning
magnet has analogies with protons and
neutrons which can be in traps or atomic
particles which could be in magnetic
traps so it is used but not quite in
this toy like form i just i found i'm
addicted to this
you