The earth means many things to the people who live on it. To a farmer, the earth is rich soil. To a road builder, the earth means mountains of hard rock. For a sailor, the earth is water as far as the eye can see. A pilot's view of the earth may include part of an ocean, a mountain, and patches of farmland. An astronaut speeding through space sees the earth's shape and the outline of lands and oceans. Each of these different views helps describe the earth but none really tells what the earth is.