On Tue, Mar 3, 2020 at 10:23 AM H LV <hveeder...@gmail.com> wrote: > At the time of Galileo it was argued the Earth could not be spinning > because this motion would result in an observable effect on the trajectory > falling bodies. For example if the Earth were turning eastward at hundreds > of miles per hour then a cannon ball dropped from a tower would not fall > vertically but would hit the ground west of the tower. In otherwords the > ball would not be able to keep up with the motion of the Earth. To counter > this argument Galileo formulated a thought involving a ship in his > Dialogue Concerning the Two Chief World Systems : > > <<Shut yourself up with some friend in the main cabin below decks on some > large ship, and have with you there some flies, butterflies, and other > small flying animals. Have a large bowl of water with some fish in it; hang > up a bottle that empties drop by drop into a wide vessel beneath it. With > the ship standing still, observe carefully how the little animals fly with > equal speed to all sides of the cabin. The fish swim indifferently in all > directions; the drops fall into the vessel beneath; and, in throwing > something to your friend, you need throw it no more strongly in one > direction than another, the distances being equal; jumping with your feet > together, you pass equal spaces in every direction. When you have observed > all these things carefully (though doubtless when the ship is standing > still everything must happen in this way), have the ship proceed with any > speed you like, so long as the motion is uniform and not fluctuating this > way and that. You will discover not the least change in all the effects > named, nor could you tell from any of them whether the ship was moving or > standing still. In jumping, you will pass on the floor the same spaces as > before, nor will you make larger jumps toward the stern than toward the > prow even though the ship is moving quite rapidly, despite the fact that > during the time that you are in the air the floor under you will be going > in a direction opposite to your jump. In throwing something to your > companion, you will need no more force to get it to him whether he is in > the direction of the bow or the stern, with yourself situated opposite. The > droplets will fall as before into the vessel beneath without dropping > toward the stern, although while the drops are in the air the ship runs > many spans. The fish in their water will swim toward the front of their > bowl with no more effort than toward the back, and will go with equal ease > to bait placed anywhere around the edges of the bowl. Finally the > butterflies and flies will continue their flights indifferently toward > every side, nor will it ever happen that they are concentrated toward the > stern, as if tired out from keeping up with the course of the ship, from > which they will have been separated during long intervals by keeping > themselves in the air. And if smoke is made by burning some incense, it > will be seen going up in the form of a little cloud, remaining still and > moving no more toward one side than the other. The cause of all these > correspondences of effects is the fact that the ship's motion is common to > all the things contained in it, and to the air also. That is why I said you > should be below decks; for if this took place above in the open air, which > would not follow the course of the ship, more or less noticeable > differences would be seen in some of the effects noted.>> > > This is a good argument that a spinning Earth won't result in falling > bodies being left behind but should it also be enshrined as a fundamentally > true principle of motion? > > Harry >
I mean it is one thing to argue that a revolving Earth and all bodies resting on the ground or in free fall share the same velocity as the ground. It is quite another to teach that all motion is relative. Harry
