Falling Bodies and Pendular Motion

Abstract

In the reading selection that follows, Galileo continues his treatment of falling bodies. Why, he asks, do small objects typically fall more slowly than large objects through the same medium? For example, a tiny sand grain will fall slowly through water, while a pebble having the same specific gravity will fall rapidly. Buoyancy effects, which had been previously considered, cannot account for this phenomenon. The discussion between Salviati, Sagredo and Simplicio quickly turns to the motion of swinging pendula—a related phenomenon which offers important insights into this notoriously difficult problem. As the reader will perhaps notice, a short section of Galileo“s text (consisting of pages /123–127/) has been omitted, for the sake of brevity, between the previous and the current reading. In these omitted pages, Galileo describes two ingenious methods for measuring the specific gravity of air. It is these experiments to which Simplicio initially refers.

I am encouraged by the example of Aristotle whom I admire especially because he did not fail to discuss every subject which he thought in any degree worthy of consideration.

—Galileo Galilei