I want to try explaining about the earth.Earth is the currently only one place where life is known to exist.Earth is the third planet from the sun.It is also the largest of the solar system's four terrestrial planets.Earth also have one satellite that is moon.The ages of the earth is estimated to reach 4.6 billion years old.Earth also have a layer of air (atmosphere) and magnetic field is called (magnetosphere), and protect the earth's surface from solar wind, ultraviolet rays, and radiation from outer space.Air layer are divided into Troposphere, Stratosphere, Mesosphere, Thermosphere,and Exosphere.The surface of earth almost 70% is water and 20% island.Earth in the past is very good,like the climate condition, weather and temperature of the earth's still stabil, air pollution not bigger than now.But today, the earth situation is very bad, unbalance of ecosystems on the earth, clean water is difficult to obtain,and climate change be uncertain.