Wednesday, November 4, 2009
The Earth belongs to a family of nine planets, each of which is in orbit (traveling) around the sun. Together they make up the solar system, which also includes the moon orbiting around their planet, lumps of rock called asteroids, and comets with long trails of dust and gas.
The sun, the star at the center of the solar system, is a burning hot ball of shining gas. Without its heat and light, the Earth would be a frozen, dead world. Among the nine planets that orbit the sun, the Earth is unique. Only the Earth has water in its oceans and enough oxygen in its atmosphere to support animals life. Mercury, Venus, Mars, and Pluto are rocky waters. The giant planets Jupiter, Saturn, Uranus, and Neptune are globes of the gas and ice particles. The Earth is habitable because it is at just the right distance from the Sun. A little closer and it would resemble fiery Venus. A little farther away and it would be a permanent frozen waste.
The Earth, however, has not always been how it is now. Soon after it formed, about 4.6 billion years ago, this planet was a roasting cauldron. Over million of years the surface cooled and the atmosphere, ocean, and continents formed. Life began in the ocean about 3.5 billion years ago with tiny, microscopic life-forms. Many scientists think that animals and plants started to live on the land about 400 million years ago.
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came here to visit....btw, I would like to ask a favor if you could help us vote for my daughter…if you have time….your help is much appreciated….thanks!
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