No one really knows how the Earth started, but the most common theory is the Big Bang Theory. The cosmic explosions spread all the different types of matter and formed planets. Early Earth was uninhabitable by humans because of all scalding rocks and chocking fumes. The environment was hostile and violent. Since then the Earth has cooled down. The continents finally drifted, and the mountains rose and eroded. There are many theories for how the moon formed, but the one people accept most is that a Mar sized object crashed into Earth and collected some mutual gravitational force. One piece of evidence is that one side of the moon is different looking than the other because of the crash. There are two types of eclipses, lunar and solar. A solar eclipse is when the moon moves between the sun and Earth,unlike a Lunar eclipse when the earth is between the sun and moon. Past asteroids have made a big impact in the past. The theory for the extinction of dinosaurs is based of the fact that a large asteroid hit the Earth and wiped out the entire existence. Other large and important events that have occurred from meteor and asteroid impacts include: construction of the moon/earth, the origin of water, and other mass extinctions.