Definitions of Gravity, Weight and Lightness
The four 'accidental powers', and heavy and light as motion toward or away from the world's centre
A page of theoretical definitions rather than diagrams. Leonardo names the four 'accidental powers' — gravity, force, accidental motion and percussion — as the sources by which all evident works of mortals come to be and pass away. He defines gravity as an accidental power created by motion and infused into bodies displaced from their natural place, and treats heaviness and lightness as equal, opposite powers: the heavy body moves by the shortest path to the centre of the world, the light body flees from it. A small boxed marginal note pairs the words water and air (acqua - aria).
On this page
The four accidental powers
Gravity, force and accidental motion, together with percussion, are named as the four accidental powers by which all the evident works of mortals have their being and their death.
Definition of gravity
Gravity is defined as an accidental power created by motion and infused into bodies that stand outside their natural place.
Heavy and light as opposite powers
Gravity and lightness are equal powers created by one element transferred into another, so alike they may be named as one; a heavy body, when free, moves to the centre of the world by the shortest way.
Marginal note: water and air
A boxed note pairs the words water and air. The accompanying text defines the light body as one that, being free, flees from the centre of the world, each power being equal to the other.