Ptolemäus oder Kopernikus? Eine Studie über die Bewegung der Erde und über den Begriff der Bewegung

Abstract

THE author of this little book aims at showing that all motion is relative, and that the people who three hundred years ago disputed as to whether the earth moved round the sun or the sun round the earth were all equally right, and wrere only fighting about words. In the first chapter it is set forth with needless prolixity how all apparent phenomena produced by the omotion of an observer will be the same if he is at rest, and all the surrounding objects are in motion with the same velocity in the opposite direction. The author next deals with the system of Copernicus, and points out how it could only claim to represent the planetary motions in a somewhat simpler manner, but that the relative positions of the earth and a planet were exactly the same according to the old and the new system. But everything was changed by the discovery of the proper motions of the fixed stars, which made it theoretically impossible to refer, the celestial motions to a fixed origin of coordinates, while the sun's own motion through space shows that the earth cannot describe a closed curve round it. As regards the rotation of the earth, the author maintains that the deviation of a falling body towards the east and Foucault's pendulum do not absolutely prove that it is the earth and not the whole rest of the universe which is turning. Whether we say that the earth or the heavens, or both, move is thus a mere matter of taste depending on the point of view; and the two first laws of motion are incapable of proof, since there is no such thing anywhere as motion in a straight line.