Earth is the Only Planet Known to Harbor Life

Earth is the only planet on which water can exist in liquid form on the surface (though there may be liquid ethane or methane on Titan's surface and liquid water beneath the surface of Europa). Earth has a modest magnetic field produced by electric currents in the outer core. Earth is the only planet whose English name does not derive from Greek/Roman mythology. Earth's atmosphere seen at the limb.The Earth's atmosphere is 77% nitrogen, 21% oxygen, with traces of argon, carbon dioxide and water. Earth is the only planet known to support life and to have liquid water at the surface.ClimateClimate change no equal opportunity affect on continents. But despite rising awareness, misconceptions abound about the realities of what scientists prefer to call climate change. Scientists agree the Earth's climate is being directly affected by human activity, and for many people around the world, these changes are having negative effects.

How climate change is affecting communities around the world. Between 800 million and 600 million years ago, during a time called the Precambrian, Earth experienced several extreme climate changes called ice ages or glacial epochs. Glaciers began forming in Antarctica about 35 million years ago, but the climate there was warm enough for trees to grow until about 5 million years ago. The climate grew so cold that some scientists believe Earth nearly or completely froze several times. The advances alternated with periods when the climate was warmer and the ice melted. Many scientists also believe that variations in the amount of carbon dioxide in the atmosphere are responsible for long-term changes in the climate.AtmosphereMost of the mass of the Earth is in the mantle, most of the rest in the core; the part we in habit is a tiny fraction of the whole (values below x10^24 kilograms): atmosphere = 0. There was probably a very much larger amount of carbon dioxide in the Earth's atmosphere when the Earth was first formed, but it has since been almost all incorporated into carbonate rocks and to a lesser extent dissolved into the oceans and consumed by living plants.Earth is the third planet from the Sun and the only one in the solar system known to harbor life. Earth is a small planet in the vastness of space.

Earth's moon has a diameter of 2,159 miles (3,474 kilometers) -- about one-fourth of Earth's diameter. Earth has a diameter of about 7,900 miles (12,700 kilometers). Earth's orbit lies on an imaginary flat surface around the sun called the orbital plane. Earth, our home planet, has oceans of liquid water, and continents that rise above sea level. Earth takes 24 hours to spin completely around on its axis so that the sun is in the same place in the sky. Earth's axis is not straight up and down, but is tilted by about 23 1/2 degrees compared to the orbital plane. Earth and the solar system are part of a vast disk of stars called the Milky Way Galaxy.