1. The Department of Physics Short Foucault Pendulum

2. The operating Foucault pendulum in the foyer of the MacNaughton building is both a work of art and an enchanting mechanical device. That it illustrates the rotation of the earth is described on the dedication plaque on the pillar supporting the pendulum.

3. History
In 1851 the astronomer Jean Bernard Leon Foucault, while working on a conical pendulum clock to regulate a telescope drive, realized that with an ideal pendulum
supported at the north pole "the motion of the earth, which forever rotates from west to east, will become appreciable in contrast with the fixity of the plane of
oscillation".

4. Foucault’s first experiments were with a 2 m pendulum in his basement but he quickly went on to construct a 67 m pendulum at the Pantheon in Paris. This pendulum created a sensation at the Paris exhibition in 1851 and generated both a flood of experiments around the world and an enormous scientific literature.
The Pantheon-Paris

5. These effects decrease as the pendulum is made longer.
The motion of a pendulum is very sensitive to a wide variety of subtle effects which, although small, are larger than the forces that arise from the rotation of the Earth.
These effects decrease as the pendulum is made longer.
Hence most Foucault pendula on public display are many meters in length, such as the one in the UN building in New York.

6. It is very difficult to make a short Foucault pendulum like the one at the University of Guelph and have it operate accurately.
The method of doing so was solved in 1995 by Prof. H. R. Crane at the Univ. of Michigan.

7. Our pendulum was built according to Crane’s design by the late Tom Riddols a master instrument maker in the U. of G. Physics Workshop.
Tom Riddols (left) and Univ. President Rozanski (right) at the unveiling of the pendulum in 1995 to celebrate 100 years of Physics at Guelph

8. The painstaking work of adjusting the pendulum to cancel out the competing effects was accomplished by Prof. B. G. Nickel.
Although, over a period of days there are periodic and aperiodic variations of the rate of rotation of the pendulum (not all of which are understood) The average advance is within a few percent of the correct value for our latitude (see the line in the figure at the right).

9. The End
J. Hunt 2004