Mach clearly recognized the weak points of classical mechanics, and thus came close to demand a General Theory of Relativity – and this almost half a century ago! […] The contemplations of Newton's experiments with the bucket demonstrate how close his mind was to the demands of relativity in a wider sense (relativity of accelerations). Admittedly, the vivid conciousness was missing that […] we are not in a position to decide by experiments if the falling of a body relative to a coordinate system is caused by the presence of a gravitational field or by a state of acceleration of the coordinate system.