ON THE MOTIONS

NATURAL

Depending on Gravity.

A BOOK

BY GIOVANNI ALFONSO BORELLI.

The motions of sublunary bodies occur in a fluid medium, a subject which no one has treated until now.

original: "Motus Corporum sublunarium in medio fluido fieri, de quibus hactenus nemo tractauit." Borelli asserts that while previous scholars studied motion in a vacuum or theoretically, he will focus on how real-world fluids like air and water affect movement.

CHAPTER I.

A large decorative woodcut initial 'E' contains a scene with a figure, possibly in a garden or architectural setting with foliage.

It is most evident that the movements of sublunary bodies A term from traditional physics referring to the region "below the moon," which includes the Earth and its atmosphere. must take place in some space. This space must not be filled or occupied by hard, solid, or entirely continuous bodies. This is because two bodies cannot occupy the same space at the same time original: "duo corpora se mutuò penetrare nequeunt"; this is the classic physical principle of the impenetrability of matter.. Therefore, it is necessary that the space in which a body must move is either completely empty, or at least occupied by some body that can be displaced, is fluid, or is divided into small particles. Such a substance can be easily moved from its place to make room for the body that is entering and moving through it. This region surrounding the Earth is occupied by these fluid bodies, such as water, air, and fire, in which the motions of sublunary bodies occur.

Concerning the natural motions of bodies that take place in a fluid medium, namely by what reason, and by what,