At night, you look up and into the sky and see a big bright celestial body. To different people the Moon is known as a pumpkin in the sky, the trigger for werewolves, and even big cheese in the sky. Whatever you may believe, you still know it as — the Moon. But, what you may not know is how it formed. Many Scientists believe that the Moon formed as a result of the "giant impact" theory. It is exactly what it sounds like. Approximately 4.5 billion years ago, Earth collided with a Mars-sized planet; hence, the "giant impact." After the impact, a significant amount of vaporized rock from Earth injected into orbit around Earth. Once the vaporized rock cooled and condensed, it formed a ring of small, solid bodies which came together to form the Moon. Because the small bodies fixed together so quickly it created a lot of energy, which caused much heat. As a consequence, the Moon melted creating an "ocean" of magma (melted rock).
Similar to how the Earth cooled and solidified, the magma ocean of the Moon did too. Dense, iron-rich materials sank deep into the Moon, cooling and solidifying to form the mantle: the layer of rock beneath the crust through a great span of time.
As the crust formed, asteroids impacted it heavily. The South Pole-Aitken Basin, one of the largest known impact craters in the solar system, was created by such a collision.
Now, when you look up into the sky at night, you can glide your eyes with confidence over the Moon, knowing the most accepted theory of how it formed: the giant impact theory.