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Kansas State Capitol - Foucault Pendulum

Capitol dome, circa 1910The Kansas State Capitol was once the home of the world's "tallest pendulum." On November 15, 1945, Dr. George W. Davis of Ottawa hung a 105-pound lead weight, which was attached to a 163-foot piece of number 14 wire. This was suspended to the ground floor from the inner dome of the Capitol. At 9 a.m. each morning, custodian L. D. Robinson would start the pendulum swinging back and forth in a 14-foot swath across the floor. Later in the day the pendulum would be swinging in a path well off the original course. What did this mean?

In 1851 physicist Léon Foucault came up with the idea to prove a long-known belief that the earth rotates on its axis. Foucault knew that a pendulum that is supported so as to be free to swing in any plane will tend, because of its inertia, to keep on swinging in the same direction. Therefore, if the earth were stationary, an undisturbed pendulum would continue to swing in the same direction until friction finally stopped it. But if the earth rotates, a swinging pendulum would appear to change direction according to the earth's rotation.

Numerous changes were made to perfect the performance of the pendulum. Davis used plow discs and filled them with melted lead. Robinson was quoted as saying, "We tried piano wire on the first one and it wouldn't hold the weight. I had to send three or four workmen up to the dome with some heavier wire. We used a 105-pound weight first. Now the pendulum weighs 205 pounds and works all right." The swivel from which it hung had to be oiled to minimize friction. Measurements were made and proved that the pendulum had not varied from its orbit of 1/100 of an inch.

There were at least eight other Davis-placed Foucault pendulums throughout the United States including at Yale, Princeton, and the University of Chicago. Others were at the Museum of Science in Washington, D.C., Griffith Park Museum in Los Angeles and Berry school in Berry, Georgia, plus another in Kansas at the Franklin County Courthouse. Foucault's original pendulum was displayed in the Panthéon in Paris.

"It was my ambition to put one in the national capitol in Washington, Davis said. "I went there one time with my wife, Dr. Josephine Davis, who is 13 years my junior. We looked at the dome and observed where the pendulum would swing. 'Father, you can't do it,' my wife said. 'Your chart will cover the Great Seal of the United States.' I saw that she was right and decided to give it up."

While the pendulum entertained and stimulated thought-provoking onlookers, it apparently became somewhat burdensome to Robinson who had to start it each morning and patrol it to see nobody interfered with its natural motion. A railing was eventually built around it for protection. A glass enclosure was suggested by Davis but was never constructed.

"People in the statehouse are in the mood to see dignity, not to see a scientific experiment that looks like an amusement piece," Robinson said. "I think it makes the statehouse look like some kind of a grown-up county courthouse." When Robinson was once asked if it could tell time, he replied, "Yes, and no. But who cares? You can't carry a thing like that around in your pocket."

Entry: Kansas State Capitol - Foucault Pendulum

Author: Kansas Historical Society

Author information: The Kansas Historical Society is a state agency charged with actively safeguarding and sharing the state's history.

Date Created: March 2009

Date Modified: April 2011

The author of this article is solely responsible for its content.