Note 25 — Chapter V

I may, perhaps, be permitted to recall to the reader’s mind, in a note, one or two of the main objections urged by the anti-Copernicans. One of these was that it would leave the atmosphere behind, the true answer to which is that the atmosphere itself is attracted by the force of gravity to the earth, and is carried round by the rotation, as everything else is; this Galileo did not perfectly understand, as may be seen by his remarks, both in the second and the fourth day’s dialogue. Another was this—and it was put forward by no less a man than Tycho Brahé—a stone dropped from a high tower ought to fall to the westward of the tower, because the tower would be carried on to the east by the earth’s rotation, and the stone would not; this, however, being contrary to experience. The real fact is that the stone partakes of the rotatory movement as much as the tower does, the two forces of rotation and gravity being combined according to the second law of motion, while the stone is falling; this Galileo did know. Supposing a very high tower, the stone ought to fall slightly to the east, on account of the superior velocity of rotation at the top of the tower to that at the bottom. It is said this experiment has been successfully tried, as stated in note, page 55.