Earth referred to as "moons", after Earth's. The gravitational attraction between Earth and the Moon causes tides on Earth. The same effect on the Moon has led to its tidal locking: its rotation period is the same as the time it takes to orbit Earth. As a result, it always presents the same face to the planet. As the Moon orbits Earth, different parts of its face are illuminated by the Sun, leading to the lunar phases; the dark part of the face is separated from the light part by the solar terminator. Due to their tidal interaction, the Moon recedes
Sun and Moon (Middle-earth) Sun and Moon (Middle-earth) The fantasy author J. R. R. Tolkien of Middle-earth fame included Earth's sun and moon for the cosmology of his myths of Arda. These astronomical bodies appear in various versions of "The Silmarillion", a history of a world, called Middle-earth populated by Elves and other fantastic creatures as well as Men. A version of "The Silmarillion", edited by the author's son and literary executor Christopher Tolkien, was posthumously published in 1977. However the Sun and Moon already appear in the author's writings dating from the 1920s. The sun and moon in Tolkien's legendarium were described in