Leonardo distanced himself from traditional cosmology that regarded the Moon as a perfect crystal sphere emitting its own light and traveling along an orbit around the Earth encased in a solid orb. He states that the Moon receives light from the Sun. He explains its diffuse luminosity by supposing that the Sun’s rays struck the agitated waters of the vast oceans covering a large part of its surface, and were thus reflected in all directions. He also states that the dark spots observed on the Moon are due to the presence of land masses emerging from the waters. Leonardo sees the Moon as the Earth’s perfect twin and therefore composed of the same four elements (fire, air, water, earth) gravitating around its center.
Make eye-glasses to see the moon larger
Codex Atlanticus, f. 518r