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) name given to the Sun by the Noldor. A poetic name for the Sun was the Daystar, and Gollum referred to it as the Yellow Face. The Sun was seen by the Elves as made on behalf of Men, and they valued the Moon more highly. Morgoth's creatures, the Orcs, feared the Sun, and with the exception of the Uruk-hai, they did not travel while it was in the sky. The Trolls of Middle-earth feared the Sun even more, and with great reason: they turned to stone under its light. Only the later Olog-hai were able to move under the