-- The planet we call 'home'---a giant ball of rock and metal that orbits the Sun.

The Earth, our home planet, is a giant ball of rock and metal that orbits the Sun. It is one of nine planets in our solar system, which is part of the Milky Way Galaxy. The Milky Way is only a small part of the universe. At an average distance of 93 million miles (150 million km), the Earth is the third planet from the Sun. At about 7,900 miles (12,600 km), the Earth is the fifth largest planet in diameter. This makes it the largest of the inner planets. The other inner planets are Mercury, Venus, and Mars. The Earth has both a gravitational and a magnetic field. One moon orbits the Earth.

Earth is the only planet known to have the conditions to support life as we know it. These conditions include the proper temperature and atmosphere. They allow the planet to have the environment and natural resources that support life. Because of these conditions, millions and millions of different kinds of plant and animal life have developed on our planet.

The Earth has the right temperature to support life because of its distance from the Sun. The temperature on our planet is cool enough for water to stay in its liquid state, but warm enough so that only a very small percentage of its water is in its solid state, or frozen.

The Earth's atmosphere is the proper density for animals to breathe. It also allows plants to absorb the carbon dioxide they need to grow. The atmosphere also allows sunlight to reach our planet's surface, but blocks certain kinds of harmful radiation from the Sun.

The Earth's surface consists of a thin layer of rock called the crust. Oceans cover three-quarters of our planet's surface and help keep it from getting too hot or too cold. There is hot rock beneath the crust. The center of the Earth is probably made of iron and nickel. It is very hot - about 11,000 degrees F (6,000 C).

The Earth orbits the Sun at about 18 1/2 miles per second (30 km/sec). Our planet's motion was used to determine the lengths of days and years. One day is the amount of time it takes the Earth to spin around its axis one time. One year is the amount of time it takes our planet to orbit around the Sun one time. The seasons on Earth are not caused by its distance from the sun, but from the way it is tilted.

Back to top

Return