The following sections of this BookRags Literature Study Guide is offprint from Gale's For Students Series: Presenting Analysis, Context, and Criticism on Commonly Studied Works: Introduction, Author Biography, Plot Summary, Characters, Themes, Style, Historical Context, Critical Overview, Criticism and Critical Essays, Media Adaptations, Topics for Further Study, Compare & Contrast, What Do I Read Next?, For Further Study, and Sources.
(c)1998-2002; (c)2002 by Gale. Gale is an imprint of The Gale Group, Inc., a division of Thomson Learning, Inc. Gale and Design and Thomson Learning are trademarks used herein under license.
The following sections, if they exist, are offprint from Beacham's Encyclopedia of Popular Fiction: "Social Concerns", "Thematic Overview", "Techniques", "Literary Precedents", "Key Questions", "Related Titles", "Adaptations", "Related Web Sites". (c)1994-2005, by Walton Beacham.
The following sections, if they exist, are offprint from Beacham's Guide to Literature for Young Adults: "About the Author", "Overview", "Setting", "Literary Qualities", "Social Sensitivity", "Topics for Discussion", "Ideas for Reports and Papers". (c)1994-2005, by Walton Beacham.
All other sections in this Literature Study Guide are owned and copyrighted by BookRags, Inc.
Tidal forces are responsible for the ocean tides we observe on Earth. One of the earliest problems considered by physicists was why Earth has two high tides per day. Galileo was unable to understand or explain this, but Isaac Newton eventually solved the problem using his theory of gravitation. The solution to the problem is that high tides are caused by the differences between the gravitational forces on Earth's water applied by Earth, the Moon, and the Sun. The water closest to the Moon is pulled toward the Moon, and Earth is also pulled toward the Moon, away from the water furthest from the Moon. This leads to an oval-shaped distribution of water around the earth, rather than a uniform spherical shape, with the thickest parts of the oval along the line between Earth and the Moon. Because Earth is rotating, a point on its surface crosses the line between Earth and the Moon twice a day, where the height of the water is at its maximum. The Sun also exerts tidal forces which are approximately half as large as those due to the Moon. This is the reason for the high and low tides that we observe.