CHAPTER 2

SPACE AND TIME

Our present ideas about the motion of bodies date back to Galileo and Newton.

Before them people believed Aristotle,

who said that the natural state of a body was to be at rest and that it moved only if driven by a force or impulse.

It followed that a heavy body should fall faster than a light one,

because it would have a greater pull toward the earth.

The Aristotelian tradition also held that one could work out all the laws that govern the universe by pure thought:

it was not necessary to check by observation.

So no one until Galileo bothered to see whether bodies of different weight did in fact fall at different speeds.