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Solar SystemEarth

© Don Dixon, Griffith Observatory

Our home planet is a small, rocky world enveloped by a life-sustaining atmosphere. Roughly two-thirds of its surface is submerged in water. The rest is divided into mountains, plains, and deserts. Our closest neighbor in space is the Moon, a lifeless, barren place roughly one-quarter Earth’s diameter.

Earth’s billions of people live in hundreds of thousands of cities, villages, and rural areas. In 1969, we took our first steps on another world when two men walked on the Moon.

The Scale of Earth and the Moon

© NASA© NASAIf you traveled once around Earth’s equator, your trip would cover 24,900 miles (40,000 km). The Apollo astronauts crossed 238,000 miles (383,000 km) to reach the Moon during their missions.

Until relatively recently, most people had not ventured such great distances. There are still those who do not leave their home countries. Some rarely move far from their birthplaces.

Through most of history, travel around our planet took place on great expeditions that lasted months or years. Today, airplanes cover large distances in a matter of hours. To go beyond Earth to the Moon and planets requires spacecraft.

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