SECTION 2.
THE EARTH NO AXIAL OR ORBITAL MOTION.
If a ball be allowed to drop from the mast-head of a ship at rest, it will strike the deck at the foot of the mast. If the same experiment be tried with a ship in motion, the same result will be observed. Because, in the latter case, the ball is acted upon simultaneously by two forces at right angles to each other—one, the momentum given to it by the moving ship in the direction of its own motion, and the other the force of gravity, the direction of which is square to that of the momentum. The ball being acted upon by the two forces together will not go in the direction of either, but will take a diagonal course, as shown in the following diagram, [Figure 22].
FIG. 22.
FIG. 23.
The ball passing from A to C by the force of gravity, and having at the moment of its liberation received a momentum from the ship in the direction A B, will by the conjoint action of the two forces, take the direction A D, falling at D, just as it would have fallen at C had the vessel remained at rest. In this way, it is contended by those who hold that the Earth is a moving sphere, a ball allowed to fall from the mouth of a deep mine reaches the bottom in an apparently vertical direction, the same as it would if the Earth were motionless. So far, there need be no discussion—the explanation is granted. But now let the experiment be modified in the following way:—Let the ball be thrown upwards from the mast-head of a moving vessel; it will partake as before of two motions, the upward and the horizontal, and will take a diagonal course upwards and with the vessel until the two forces expend themselves, when it will begin to fall by the force of gravity only, and drop into the water far behind the ship, which is still moving horizontally. Diagram [Figure 23] will illustrate this effect. The ball being thrown upwards in the direction A C, and the vessel moving from A to B, will cause it to pass in the direction A D, arriving at D when the vessel reaches B; the two forces having expended themselves when the ball arrives at D, it will begin to descend by the force of gravity in the direction D B H, but during its fall the vessel will have reached the position S, so that the ball will drop far behind it at the point H. To bring the ball from D to S two forces would be required, as D H and D W; but as D W does not exist, the force of gravity operates alone, and the ball necessarily falls behind the vessel at a distance proportionate to the altitude attained at D, and the time occupied in falling from D to H.
The same result will be observed on throwing a ball directly upwards from a railway carriage when in rapid motion, as shown in the following [Figure 24]. While the carriage or tender passes from A to B, the ball thrown from A to C will reach the position D, but while the ball then comes down by the force of gravity, operating alone, to the point H, the carriage will have advanced to W, so that the ball will always drop more or less behind the carriage, according to the force first given to it in the direction A C and the time occupied in ascending to D, and thence descending to H. It is therefore demanded that if the Earth had a motion upon axes from west to east, and a ball, instead of being dropped down a mine or allowed to fall from the mast head of a ship, be shot upwards into the air; from the moment of its beginning to descend the surface of the Earth would turn from under its direction, and it would fall behind or to the west of its line of descent. On making the experiment no such effect is observed, and therefore the conclusion is unavoidable, that the Earth DOES NOT MOVE UPON AXES!
FIG. 24.