The Works of Galileo

A New Pope and a New Dialogue

Dialogue, some representative quotations

English trans. Stillman Drake, Dialogue on the Two Chief World Systems (Modern Library, 2001).

Salviati: “Is it possible for you to doubt that if Aristotle should see the new discoveries in the sky he would change his opinions and correct his books and embrace the most sensible doctrines, casting away from himself those people so weak-minded as to ... go on abjectly maintaining everything he ever said?”

Simplicio: “The crucial thing is being able to move the Earth without causing a thousand inconveniences.”

Salviati: [You say...] “Drop a lead ball from the top of the mast of a boat at rest, noting the place where it hits, which is close to the mast; but if the same ball is dropped from the same place when the boat is moving, it will strike at that distance from the foot of the mast which the boat will have run during the time of fall.... [BUT] anyone who... [actually performs that experiment] will find that the experiment shows exactly the opposite of what is written; ... the stone always falls in the same place on the ship, whether the ship is standing still or moving.”

Salviati: “Without recourse to experiment, I am sure that the effect will happen as I tell you, because it must happen that way...”

Simplicio: “These mathematical subtleties do very well in the abstract, but they do not work out when applied to sensible and physical matters.”

Salviati: “Take note, Simplicio, just how far one may go without geometry...!”

Salviati: “The acceleration of straight motion in heavy bodies proceeds according to odd numbers beginning from one. That is, marking off whatever equal times you wish, and as many of them, then if the moving body leaving a state of rest shall have passed during the first time a space as, say, an ell, then in the second time it will go three ells; in the third, five; .... this is the same as to say that the spaces passed over by the body starting from rest have to each other the ratios of the squares of the times....”

Salviati: “we Italians are making ourselves look like ignoramuses...”

Salviati: “Nor can I ever sufficiently admire the outstanding acumen of those who have taken hold of [the Copernican] opinion and accepted it as true; they have through sheer force of intellect done such violence to their own senses as to prefer what reason told them over that which sensible experience plainly showed them to the contrary.”

Simplicio: “keeping always before my mind’s eye a most solid doctrine that I once heard from a most eminent and learned person, and before which one must fall silent, I know that if asked whether God in His infinite power and wisdom could have conferred upon the watery element its observed reciprocating motion using some other means than moving its containing vessels, both of you would reply that He could have, and that He would have known how to do this in many ways which are unthinkable to our minds.”

Exhibit revised 11/17/04.

Exhibit credit: Kerry Magruder, with the assistance of , Marilyn B. Ogilvie, Duane H. D. Roller.

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