Earth is the third planet from the sun in the Solar System. It was supposedly the only planet capable of providing a suitable environment for life until August 2011 when an Invasion of Earth took place, led by an unknown alien species. They tried to overtake the planet for its resources, supposedly, and in the process of doing so, jeopardized the human race with violence and terrorism. Earth's living inhabitants consist of humans, animals, and plant life. Earth is covered in about 71% of water and 29% of land. The Earth is the only known planet that has significant quantities of surface liquid water, which may be why it was invaded by the aliens, as they use it as a fuel. The Earth consists of 7 continents- North America, South America, Europe, Africa, Asia, and Australia, and also consists of 195 countries. The planet was form 4.54 billion years ago. There are 365 days in a year because this is the amount of time it takes for the Sun to rotate around the entire Earth. The Earth also has one moon, referred to as simply "the Moon."