ROTATION OF THE EARTH.

New Zealand Herald, Volume LXVI, Issue 20420, 23 November 1929, Page 15

ROTATION OF THE EARTH.

FAMOUS PROOF REPEATED. Foueault's experiment (proving the rotation of the earth round its axis) was repeated in Florence recently by Father Alfani, the Director of the Observatory, in Iho presence of delegates to the science congress being held in the city. Although the rotation of the earth was an accepted fact soon after, as suggested by Copernicus in the 16th century, an experimental proof * was wanting until 1851, when Foucault performed his celebrated pendulum experiment at the Pantheon, Paris. A pendulum about 200 ft. long, composed of a flexible wire carrying a heavy iron bob, was suspended so as to be free to oscillate in any direction. The bob was provided with a style which 'passed over a table strewn with fine sand, so that (lie style traced the direction in which the pendulum was swinging. It was found that the oscillating pendulum at each swing apparently deviated to the right—-demonstrating that the table was moving and therefore tno earth was rotating.

In (he southern hemisphere the deviation would be to the left. At the equator there would he no deviation, but at the poles the plane of oscillation would traverse a, complete circle in 24 hours. Since 1850 the experiment has several times been successfully tried, but, it is claimed, never in conditions so impressive as the latest demonstration in Florence. The globe of metal was suspended by a wire from a lofty roof of the Brtmelleschi dome in Santa Maria del Fiore, the point of suspension being vertically over the centre of a round table covered with sand. The pendulum was nearly 150 ft. long, and weighed about 2001b. The experiment lasted 16 minutes.