The Earth as a Star: the Moon, Water and the Sun's Image
Notes and diagrams on lunar waves, the gravity of the elements, and the sun reflected on water
A densely written sheet in brown and red ink in which Leonardo argues that the earth is itself a star, shining to the universe by the sheet of water that clothes it and reflects the sun. He extends the idea to the moon, reasoning that if its surface bears waves it must possess earth, water, air and fire like our own elements, and debating with an unnamed 'adversary' whether the moon has gravity and can fall. Small circular diagrams at the right work out how the sun's image appears on a wavy sphere, alongside marginal memoranda about money owed by Salaì and the name of a Messer Francesco da Dugnano.
On this page
The earth shines as a star by means of its water
Leonardo states that the earth, wrapped for the most part in the sphere of water, takes the image of the sun and shines out to the universe just as the other stars do, and so is itself a star. The reflecting water gives the earth the same splendour we perceive in the distant stars.
Whether the moon has earth, water and gravity
If the moon has waves, and waves require wind, and wind requires earthy vapours, then the moon must contain earth, water, air and fire like our own elements. Leonardo then reasons that since gravity is one element drawn into another, and where there are no elements there is no gravity, the moon does not weigh among its elements and cannot fall from its place.
The sun's image grows on the wave as the wave recedes
The image of the sun upon a wave of water grows as much as the wave itself diminishes in apparent size through long distance from the eye. It is a note on how reflection scales with the shrinking of the wave's figure in perspective.
The sun's image cannot fill half the moon without waves
Leonardo holds it impossible for the sun's image to be seen occupying half the lunar sphere unless the moon's surface is filled with waves. A small figure of the sun and moon with the letters r a S – p q f accompanies the argument.
Every natural action follows the briefest path
A struck-out aphorism asserting that every natural action is generated by nature in the briefest way that can be found. A companion note adds that every natural action is generated and that none can be shortened.
Reminder to record the money from Salaì
A brief memorandum at the top of the sheet reminding himself to write down the money he has received from Salaì. It sits among the scientific notes as a practical personal reminder.