THE FIRST DEMONSTRATION OF THE ROTATION OF THE EARTH AND THE INVENTION OF THE GYROSCOPE

FOUCAULT, (JEAN BERNARD LEON).

Démonstration physique du mouvement de rotation de la terre au moyen du pendule. (Commissaires MM. Arago, Pouillet, Binet). (+) Sur une nouvelle démonstration expérimentale du mouvement de la Terre, fondée sur la fixité du plan de rotation; par Léon Foucault. (+) Sur les phénoménes d'orientation des corps tournant entraînés par un axe fixe à la surface de la Terre. - Nouveau signes semsibles du mouvement diurne; par M. Léon Foucault. (+) Démonstration expérimentale du mouvement de la terre. Addition auc communications faites dans les précédentes séances; par M. Léon Foucault. (Extrait du Journal des Débats du mercredi 22 septembre 1852). (+) Sur la tendance des rotations au parallélisme; par M. Léon Foucault. (5 papers).

(Paris, Bachelier, 1851-52). 4to. Later blank wrapper. Extracted from "Comptes rendus hebdomadaires des séances de l’Académie des sciences", Vol. 32 and vol. 35. Foucault's papers: pp. 135-138 (1851, vol. 32), pp. 421-424 (1852, vol. 35), pp. 424-427 (1852, vol. 35), pp. 469-470 (1852, vol. 35) and p. 602 (1852, vol. 35).

First appearance of the papers in which Foucault presented his discovery of the proof of the rotation of the earth by the large pendulum, called FOUCAULT'S PENDULUM. It was presented by Arago at the meeting of the Acadey of Scieces on February 3, 1851 (the first paper offered). In the third paper offered, "Sur les phénoménes d'orientation des corps tournant entraînés par un axe fixe...", Foucault presents his invention of the GYROSCOPE, a freely spinning flywheel, which constitutes a different method of demonstrating the rotation of the Earth; he furthermore correctly predicts the use of the gyroscope as a compass. The word "gyroscope" was coined by Foucault (on p. 427 of the third paper), taken from the Greek, meaning "to look at the rotation".

Since Léon Foucault's public demonstration of his pendulum experiment, it has played a prominent role in physics, physics education, and the history of science. The Foucault pendulum is a long pendulum suspended high above the ground and carefully set into planar motion. The phenomenon described by Foucault1 concerns the orientation of the plane of oscillation of the pendulum.

"The experiment (with the pendulum) caused great excitement at the time. Heracleides had first suggested twenty-two centuries before that the earth was rotating and Copernicus had renewed the suggestion three centuries before. Since the time of Galileo two and a half centuries before, the world of scholarship had not doubted the matter. Nevertheless, all evidence as to that rotation had been indirect, and not until Foucault's experiment could the earth's rotation actually be said to have been demonstrated rather that deduced."

"Continuing to experiment on the mechanics of the earth's rotation, Foucault in 1852 invented the gyroscope, which, he showed, gave a clearer demonstration than the pendulum of the earth's rotation and had the property, similar to that of the magnetic needle, of maintaining a fixed direction. Foucault's pendulum and gyroscope had more than a popular significance (which continues to this day). First, they stimulated the development of theoretical mechanics, making relative motion and the theories of the pendulum and the gyroscope standard topics for study and investigation. Second, prior to Foucault's demonstrations the study of those motions on the earth's surface in which the deflecting force of rotation plays a prominent part (especially winds and ocean currents) was dominated by unphysical notions of how this force acted. Foucault's demonstrations and the theoretical treatments they inspired showed conclusively that this deflecting force acts in all horizontal directions, thus providing the sound physical insight on which Buys Ballot, Ferrel, Ulrich Vettin, and others could build. (DSB).

PMM: 330 lists the offprint with the title "Sur Divers Signes Sensibles du Mouvement Diurne de la Terre" - Barchas Collection, 738 (the periodical version, but only the first paper) - Dibner, No. 17 (offprint version).

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