地球属于太阳系的一员，地质学家认为地球大致形成于46亿年前。最开始地球只是一块岩石，它以微弱的引力不断地吸引了一些尘埃和碎石，质量渐渐变大。随着地球的质量越来越大，在星体的引力均衡作用下，它就成了一个球体。地球在吸引尘埃碎石的过程中，慢慢清理了其轨道上的其他天体，经受的小行星撞击次数也越来越少。于是地球的温度开始下降，表面的岩层开始形成，大气层中的水蒸气也开始冷凝成雨水降落到地面上，原始的海洋开始形成，我们的地球也随之形成。
The Earth is a member of solar system. Geologists believe it formed about 4.6 billion years ago. The Earth was a rock at the very beginning . Its weak gravity constantly pulled in dust and gravel and gradually its mass gained. As the Earth became more and more massive, it became a sphere under the influence of gravitational equilibrium of stars. It slowly cleaned up other objects in its orbit as it pulled in dust and gravel, which led to fewer asteroid collision. As a result, temperature of the Earth began to drop and the surface stratum started to form. Water vapor in the atmosphere condensed into rain and fell to the ground and primordial ocean began to form. That’s the formation of our planet.
