精选优质文档-倾情为你奉上HOW LIFE BEGAN ON THE EARTHNo one knows exactly how the earth began, as it happened so long ago. However, according to a widely accepted theory, the universe began with a Big Bang that threw matter in all directions. After that, atoms began to form and combine to create stars and other bodies. For several billion years after the Big Bang, the earth was still just a cloud of dust. What it was to become was uncertain until between 4.5 and 3.8 billion years ago when the d
