Fig2_3 Tides

Fig2_3 Tides

Fig. 2.3 . The Moon's gravitational attraction causes two tidal bulges in the Earth's ocean water, one on the closest side to the Moon and one on the farthest side. The Earth's rotation twists the closest bulge ahead of the Earth-Moon line (dashed line), and this produces a lag between the time the Moon is directly overhead and the time of highest tide. The Moon pulls on the nearest tidal bulge, slowing the Earth's rotation down. At the same time, the tidal bulge nearest the Moon produces a force that tends to pull the Moon ahead in its orbit, causing the Moon to spiral slowly outward.

Copyright 2010, Professor Kenneth R. Lang, Tufts University