Unit 4　Astronomy：the science of the stars

　　地球是太阳系中唯一有生命存在的行星，你知道是什么原因吗？

　　The solar system

　　In the galaxy－of its solar system inside，conceive the life，that life the planet，is the Earth.The Sun gives out lights to have fever，its shining glory，good enough to illuminate whole solar system！In regard to life，want to exit，must have the position just right of the water，the Earth around the Sun，not cold not hot.The water can reserve over a long period of time at on the earth，the living creature is just can multiply greatly.

　　Venus，although were called the Venus，it to life，ruthlessness and matchless.Over hot of temperature，make the humidity difficult then reserve，atmosphere temperature over high，have not any life form.

　　A life planet is the Earth，solar system unique.The temperature is just right；humidity quilt the permafrost atmosphere reserve，at the same time，the atmosphere can still rise to prevent a part of meteors bump the shot permafrost the threat.

　　Mars，ever thought there was life on it，is the god of War.The planet probably got this name due to its red color.The surface of Mars is much colder than the Earth would be at that distance from the Sun.

　　The other's planet, because leave the Sun too much faraway, the surface temperature is all at below zero 200 degree, therefore also is not suitable for the existing of life.Therefore, solar system the

inside were confirmed for the planet that have life, contain 1 the Earth.