Overview

Earth is a beautiful planet. Even from space we can see its beauty--blue seas, green jungles, red deserts, and white clouds. Much of our appreciation of the Earth comes from knowing that it is home for us and the billions of other living things that share this special and precious corner of the Universe. But why study Earth in an astronomy course? The reason is simple: we know Earth better than any other astronomical body, and we can learn from it about many of the properties that shape other worlds.

Earth's special characteristics result in large measure from its dynamic nature. The Earth is not a dead ball of rock; both its surface and its atmosphere have changed greatly during its vast lifetime. Below our feet the ground sometimes trembles and wrenches in response to dynamic forces even today, crumpling our planet's crust into mountains, stretching it, and tearing it open to form new ocean basins.

These slow but violent motions within the Earth arise from heat generated deep within. That heat also drives volcanic eruptions, which vent gases and molten rock. Over billions of years, such gases accumulated, in part creating our atmosphere, an atmosphere that has itself been changed by the presence of abundant water and life.