Foucault Pendulum at National Museum of History and Technology

ID: SIA Acc. 11-009 [75-3965]

Creator: Harrell, Alfred

Form/Genre: Color negatives

Date: 1975

Citation: Smithsonian Institution Archives, Acc. 11-009, Image No. 75-3965

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  • On exhibition January 1, 1964 - October 30, 1998.
  • Modeled after French physicist J. B. L. Foucault's 1851 pendulum, the museum's pendulum demonstrates the axial rotation of the earth. The 240-pound brass, hollow bob is suspended by a 54-ft. steel cable from the ceiling of the 4th floor. Although the pendulum's vertical plane seems to change, in fact it remains fixed. What is actually moving is the floor, which rotates under the pendulum because of the Earth's rotation. As the Earth moves, the red markers, arranged in a circle around an inlaid compass rose, move into the path of the pendulum, and the bob knocks them over one by one.


  • Smithsonian Institution Office of Printing and Photographic Services
  • National Museum of History and Technology

Cite as

Smithsonian Institution Archives, Acc. 11-009, Image No. 75-3965

Repository Loc.

Smithsonian Institution Archives Capital Gallery, Suite 3000, MRC 507; 600 Maryland Avenue, SW; Washington, DC 20024-2520


  • 1975
  • March 13, 1975

Restrictions & Rights

  • No access restrictions Many of SIA's holdings are located off-site, and advance notice is recommended to consult a collection. Please email the SIA Reference Team at
  • No Copyright - United States


  • Exhibitions
  • Foucault's pendulum


Color negatives

Local number

SIA Acc. 11-009 [75-3965]

Physical description

4 x 5;

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