EARTH

For a space traveler, the distinguishing Earth features are the blue waters, brown and green land masses and white clouds set against a black background. Many dream of traveling in space and viewing the wonders of the universe. The Earth orbits the Sun at a speed of about 110,000kmph. In reality all of us are space travelers. Our spaceship is the planet Earth, traveling at the speed of 108,000 kilometers (67,000 miles) an hour.

Earth is the third planet from the Sun,about 150 million km away. It is not so close to the Sun that it is scorhing hot, nor so far away that it is icy cold. It has water on its surface, and can sustain life.From the perspective we get on Earth, our planet appears to be big and sturdy with an endless ocean of air. From space, astronauts often get the impression that the Earth is small with a thin, fragile layer of atmosphere. 70% of the Earth is ocean.

The Earth is tilled. It takes 365.256 days for the Earth to orbit the Sun once. Earth is the only planet in the solar system known to harbor life. Every four years its a leap year it has 366.265 days. Our planet's rapid spin and molten nickel-iron core give rise to an extensive magnetic field, which, along with the atmosphere, shields us from nearly all of the harmful radiation coming from the Sun and other stars. Earth's atmosphere protects us from meteors, most of which burn up before they can strike the surface.