太陽系八大行星之一,地球自西向東自轉,同時又圍繞太陽公轉.地球自轉與公轉運動的結合使其產生了地球上的晝夜交替和四季變化(地球自轉和公轉的速度是不均勻的).同時,由于受到太陽、月球、和附近行星的引力作用以及地球大氣、海洋和地球內部物質的等各種因素的影響,地球自轉軸在空間和地球本體內的方向都要產生變化.地球自轉產生的慣性離心力使得球形的地球由兩極向赤道逐漸膨脹,成為目前的略扁的旋轉橢球體,極半徑比赤道半徑短約21千米.
　　阿地球是由一系列的同心層組成.地球內部有核（地核）、幔（地幔）、殼（地殼）結構.地球外部有水圈和大氣圈,還有磁層,形成了圍繞固態(tài)地球的美麗外套.
　　地球作為一個行星,遠在56億年以前產生于原始太陽星云.
　　One of the eight planets of the solar system,the earth rotation from the west to the east,and orbit the sun.The earth rotation and the combination of the revolution movement so as to produce a day and night on earth and seasons change (the earth rotation and the speed of the revolution is not uniform).At the same time,because of the sun,the moon,and by nearby planets gravity and the earth's atmosphere,ocean and earth's internal material factors,the earth spin axis in space and the direction of the earth in the body to produce change.The earth rotation inertia centrifugal force produced by the poles of the earth makes spherical gradually expand to the equator,become the current slightly flat spin ellipsoid body,extremely radius than the equator short radius about 21 km.
　　O earth consists of a series of concentric layers.The interior of the earth have nuclear (core),curtain (mantle),shell (crust) structure.The earth's outer have hydrosphere and atmosphere,and magnetic layer,formed around of the solid earth beautiful coat.
　　The earth as a planet,far before 5.6 billion years produced in the primitive solar nebula.