Foucault pendulum

A Foucault's (also Foucault ) pendulum is a long pendulum with a large pendulous mass, by means of which the Earth's rotation can be demonstrated graphically.

Experiments and description

On January 3, 1851, the French physicist Jean Bernard Léon Foucault introduced in the basement of his home by an experiment in which he put a two-meter long pendulum in motion. It hovered close to the ground and seemed about to change in the course of time his direction. As an external force acting on the pendulum was excluded, it was not spherical, but the bottom (the earth ), which changed its direction, i.e., the bill forces the rotation of the earth by the Coriolis force.

On February 3, 1851 Foucault introduced the experiment in the Paris Observatory with a 12 meter long pendulum and on March 26, 1851 Panthéon with a 67 meter long pendulum with a 28 -pound and 60 inches diameter comprehensive pendulum bob to the public. At the lower end of the pendulum body, there was a peak that marked each oscillation a track in a sand bed on the floor. Allows an amateur USEFULLY proof of Earth's rotation has been submitted. Since that time, this attempt shear foucault pendulum experiment is called, although similar attempts had already been carried out in 1661 by the Italian physicist Vincenzo Viviani.

The sensational experiments were repeated later by Garthe in Cologne Cathedral and fword in the Speyer Cathedral. The results were not qualitatively satisfactory. Heike Kamerlingh Onnes had in his dissertation from 1877 indicate all sources of error that had occurred in these experimental set-ups.

Foucault's Pendulum still hang in various science museums. The iron ball of the original pendulum was kept until 1946 at the Conservatoire National des Arts et Métiers and then returned to the Panthéon.

At the equator, the plane of oscillation of the pendulum does not rotate at all. The farther away you get from the equator, the stronger the rotation, the geographical poles ( exit points of the axis of rotation ) it is exactly 360 degrees per sidereal day ( 23 hours, 56 minutes, 4.091 seconds ). This value explained by the fact that the earth simply rotates away at the geographic poles under the pendulum without the pendulum changes its position ( except by the rotation around the sun ).

Another interpretation is that, in relation to an earth-fixed coordinate system - that is, viewed from the natural habitat of man - the swinging pendulum angles to the oscillation direction of a Coriolis force acts on the northern hemisphere, a deviation to the right and on the southern hemisphere one to the left causes; only at the equator remains from the deflecting force. The vibration level, consequently rotates around the vertical axis through the point of suspension with the angular velocity ωv =? E · sin φ, where? E is the angular velocity of the Earth and φ the latitude of the suspension. According takes a full turn at the poles a sidereal day, in Munich ( φ about 48 ° ) about 32.2 hours.

The path of the pendulum bob describes is called a rosette orbit.

The suspension of the pendulum may be flexible ( University of Applied Sciences Hamburg), gimbal ( Humboldt -Universität zu Berlin) or stiff ( millennium tower in Magdeburg ) take place, because the pendulum one way or maintains the level of vibration in three-dimensional space, even if the suspension (inevitably rotates with the ground).

Pictures

Pendulum in the Orangerie in Kassel

Pendulum at the University of Koblenz

Pendulum in the Deutsches Museum, Munich

The same pendulum from above

Zwickau University

Pendulum in women Castle (Poland )

Pendulum in Motala (Sweden)