A Foucault pendulum is
a classical, beautiful experiment in physics, showing that Earth rotates
around its axis. When the experiment was performed for the first
time by Léon Foucault in 1851 in Paris it was the first ocular
proof for the rotation of Earth where
one
with
own
eyes could see that
earth
really rotates around its axis. Of course this was known at
this time but an obvious proof was still missing.
The pendulum in Motala is made up of a steel
bob suspended in a wire (See the picture to the right). The bob must be
suspended in a perfectly symmetric way, able to swing freely in all
directions if the experiment is going
be successful. Once the pendulum is set in movement, after a while
you can notice that the plane of the pendulum´s swing has
changed direction clockwise. The plane of swing keep changing its
direction and is making a full circle in 32 hours in Motala. Thus the
velocity of the rotation is about 13 degrees an hour.