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Astro*Dictionary by Michael Erlewine





2 articles for "Foucault Pendulum"

Foucault, Jean Bernard Leon [Astro*Index]

(foo-koh') (1819-1868) French physicist.

He worked with Fizeau in the measurement of the velocity of light by means of a toothed wheel, but later developed an improved method based on reflecting light between two mirrors, one of which was rotated at high speed. By measuring the velocity of light in air and water, he presented strong evidence in favor of the wave theory of light. He is best remembered as the inventor of the Foucault Pendulum.

See also:
♦ Axial Rotation
Foucault Pendulum [Astro*Index]

Named for the French physicist Foucault. A swinging pendulum tends to maintain its plane of oscillation; thus, as the Earth twists under it, the plane of the pendulum appears to rotate with reference to the floor of the room. The period of rotation is given by the formula:
                  P = 1440m/sin(latitude)

Thus, at the North and South poles (latitude=90°), the period is 1440m, or 24h00m. But, at the latitude of Paris, the period of one rotation is 31h47m, as measured by Foucault. As one approaches the equator, the period increases toward infinity, and the plane of the pendulum does not rotate. South of the equator the plane rotates in the opposite direction to that found in the northern hemisphere.

See also:
♦ Light, Velocity of ♦ Fizeau, Armand Hippolyte Louis


Astro*Index Copyright © 1997 Michael Erlewine