High Quality Content by WIKIPEDIA articles! Earth tide is the sub-meter motion of the Earth of about 12 hours or longer caused by Moon and Sun gravitation, also called body tide which is the largest contribution globally. The largest body tide contribution is from the semidiurnal constituents, but there are also significant diurnal constituents. There also semi-annual and fortnightly contributions due to the axial tilt. The use of the word tide is by analogy, and although the forcing is quite similar, the responses are quite different.