Earth tide Earth tide Earth tide (also known as solid Earth tide, crustal tide, body tide, bodily tide or land tide) is the displacement of the solid earth's surface caused by the gravity of the Moon and Sun. Its main component has meter-level amplitude at periods of about 12 hours and longer. The largest body tide constituents are semi-diurnal, but there are also significant diurnal, semi-annual, and fortnightly contributions. Though the gravitational forcing causing earth tides and ocean tides is the same, the responses are quite different. The larger of the periodic gravitational forces is from the Moon but that of the
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