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Foucault Pendulum


This object is a metal ball in a wooden box.

The wooden box is rectangular, with attachments for a leather strap on either side (the strap is torn off on both sides at the base). There are two metal latches on the front, and between them, a plastic sticker reading “FOUCAULT PENDULUM”.

The box hinges at the back. Inside it is divided into two containers. A smaller one contains four small components, one of which is a tube in a T shape, a thick washer with a screw thread hole through the middle, a short rod with a screw end and a small meta piece with a portion of thin wire wrapped around it. A piece of black fabric has been placed on top of these components to hold them in place.

In the second, larger, section, there is a metal ball, approximately 15cm in diameter. It is extremely heavy. There is a hole in its surface with screw threads inside. The ball is nestled in a piece of red felt.

Accession Number: 2019.ast.237

Alternative Name: Foucault’s pendulum

Primary Materials:

Metal: Iron or Iron Alloy, Textile: Cotton, Textile: Felt, Wood.


On the plastic label stuck to the front of the box: “FOUCAULT PENDULUM”

Handwritten inside the lid of the box in pencil: “Weight = 25 lbs”

On a small sticker stuck to the inside of the lid of the box: “AST35”

Dimensions (cm):

Box: Height = 20, Width = 17.5, Length = 28.


A Foucault pendulum is an experiment devised by Léon Foucault to demonstrate the rotation of the Earth. A very long pendulum with massive weight, when swung, will rotate slightly each time as the Earth turns, describing a circle at its highest points over the course of 24hrs.


Very Good: The box has smudges and nicks across its surface. There is a crack through the length of the lid. The leather strap that once was connected to both sides has broken away entirely and no part of it survives with the object.

The two fabric pieces are dirty and wrinkled but not degraded. The edges of the black cotton are frayed slightly. The small metal pieces are dulled but not rusty. The wire attached is only a small length.

The surface of the ball is slightly rusty in places, and dull/smudged in places.

Associated Instruments:


Date of Manufacture: 20th Century


This artifact may have been used for teaching at the Department for the Astronomy & Astrophysics or at the David Dunlap Observatory. If the former, it was probably moved at some point to the Observatory for storage or use. The sphere was kept at the David Dunlap Observatory until 2009. Upon the sale of the Observatory, it was moved to the University of Toronto’s Department of Astronomy & Astrophysics at the St George Campus. In 2017 it was moved to a new storage location in McLennan Physical Laboratories.

Additional Information and References:

Historical Notes: