Light and shadow between sun, moon and earth
Geometry of earthshine over a lunar month, with labelled orbit figures a, b, c
A column of concentric orbit diagrams down the right side works through the reciprocal play of light and shadow among sun, moon and earth. Leonardo proposes that the variations of light and shadow the moon presents to the earth mirror what the earth and its ocean present to the moon, and labels the bodies a (sun), b (moon) and c (earth) to trace how each sees the other darken. Successive figures pair the day and night sides of earth and moon in different alignments, and a closing note states that over about thirty days every part of the moon receives the sun, its point opposite the full moon waiting fifteen days to see the sun again.
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The moon mirrors the earth's light and shadow
The demonstration made by the variations of the moon's light and shadow toward the earth is like that which the earth and the water of our world make to the moon. Leonardo states that this can be proved.
Reciprocal darkening of sun and light (a, b, c)
Let a be the sun, b the moon, c the earth. Here the earth does not see the whole sun, and the moon's night side no longer receives the rays the ocean used to reflect back to it; so the earth sees the sun darkened and the moon's night sees our daylight darkened.
Half-day and half-night alignments (m)
In this figure half of the earth's day side sees half of the moon's day side and vice versa, while both earth and moon see the sun in the west. A companion figure repeats the case with the sun in the east and the bodies in the west.
Every part of the moon lit within thirty days
In about thirty days every part of the moon has had the sun, and the point antipodal to the full moon waits fifteen days before it sees the sun again.