It is common knowledge, though it is not proven yet, that in the great vastness of space only our planet can accommodate life. Despite being rather small in comparison to other space objects, it is definitely the most fascinating celestial body in the Universe. Earth is the only planet of its kind—it is populated by more than 7 billion people and still has many places that are unknown to us. But do you think that you know everything about our home? Do you know how many animal species have ever existed on it or why is Earth green and not purple? There are so may interesting and amazing things about our planet, that people may never know even a half of them.