EARTH IN THE SOLAR SYSTEM

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.

PLANET EARTH

Buried deep in the heart of our planet is a metal core of iron and nickel that is large than the Moon and almost as hot as the surface of the Sun. The outer layer of the core is liquid metal, but at the center enormous pressure has compressed it into a solid. When the Earth formed 4.6 billion years ago, it glowed red-hot, and the molten metals sank to its center while the lighter rocks floated to the surface.

A thick layer of the hot rock called the mantle, is wrapped around the core. This acts like a heated blanket, holding in the warmth. Around the mantel is a third layer called the crusts, which forms the rock surface of the Earth on which we live. The thickest parts of the crust are about 37 miles (60 km) deep, but if the Earth were compared to an apple, the crust would only be as thick as the apple’s skin.

The mantle contains traces of radioactive uranium, which steadily gives out heat. This warmth rises, creating a more fluid part of the mantle known as the asthenosphere. Above the asthenosphere lies the lithosphere, which includes the outermost mantle and the crust. The lithosphere is made up the massive plates that float on the fluid asthenosphere. These plates are constantly moving, causing the contenents to drift apart, mountains to form, the Earth to shake, and volcanoes to erupt.

Chameleon

Thursday, October 22, 2009

The Chameleon is a strange lizard that lives in most of Africa's forests. It changes color to camouflage itself by blending in with its surroundings. It turns dart when angry and pale when afraid.It has swiveling eyes and a long, sticky tongue for catching insects.