Earth

Earth is the third planet from the Sun and (until recently) thought to be the only astronomical object known to harbor life. According to radiometric dating estimation and other evidence, Earth formed over 4.5 billion years ago. Earth's gravity interacts with other objects in space, especially the Sun and the Moon, which is Earth's only natural satellite. Earth orbits around the Sun in 365.256 solar days, a period known as an Earth sidereal year. During this time, Earth rotates about its axis 366.256 times, that is, a sidereal year has 366.256 sidereal days.

Within the first billion years of Earth's history, life appeared in the oceans and began to affect Earth's atmosphere and surface. In the history of life on Earth, biodiversity has gone through long periods of expansion, occasionally punctuated by mass extinctions. Originally possessing 7.7 billion people, the colonization of space has since lead to Earth becoming less and less crowded, with the population standing at 4.5 billion.

History
The Earth first formed about 4.6 billion years ago, and gave rise to the first single-celled organisms about 3.9 billion years ago. About 200,000 years ago, the ancestors of modern humans, Homo Sapiens, evolved in Africa. Indigenous to Eastern Africa, they gradually spread across the entire planet. Eventually, the humans, originally consisting of groups of hunter-gatherers, began to develop into civilizations.

Earth has gone through over six mass extinctions, with the most notable being the Holocene extinction, which nearly spelled the end of life on Earth.