893

On the luminousity of the moon.

OF THE MOON AND WHETHER IT IS POLISHED AND SPHERICAL.

The image of the sun in the moon is powerfully luminous, and is only on a small portion of its surface. And the proof may be seen by taking a ball of burnished gold and placing it in the dark with a light at some distance from it; and then, although it will illuminate about half of the ball, the eye will perceive its reflection only in a small part of its surface, and all the rest of the surface reflects the darkness which surrounds it; so that it is only in that spot that the image of the light is seen, and all the rest remains invisible, the eye being at a distance from the ball. The same thing would happen on the surface of the moon if it were polished, lustrous and opaque, like all bodies with a reflecting surface.

Show how, if you were standing on the moon or on a star, our earth would seem to reflect the sun as the moon does.

And show that the image of the sun in the sea cannot appear one and undivided, as it appears in a perfectly plane mirror.

Taken from The Notebooks of Leonardo da Vinci edited by Jean Paul Richter, 1880.

Notebooks of Leonoardo da Vinci
XIV: Anatomy, Zoology and Physiology.
. . .
873
On the luminosity of the Earth in the universal space.
874,
875,
876,
877,
878
The question of the true and of the apparent size of the sun.
879,
880,
881,
882,
883,
884
Of the nature of Sunlight.
885
Considerations as to the size of the sun.
886,
887,
888,
889,
890,
891
On the luminousity of the moon.
892,
893,
894,
895,
896,
897,
898,
899,
900,
901
Explanation of the lumen cinereum in the moon.
902
On the spots in the moon.
903,
904,
905,
906,
907
On the moon’s halo.
908
On instruments for observing the moon.
909,
910
On the light of the stars.
911,
912,
913
. . .