Earth 101 | National Geographic

The Emergence and Diversity of Life00:02:06

Where there is liquid water, there is life. About 3.8 billion years ago, primitive microbial organisms emerged in Earth's oceans. Over billions of years, these evolved into a vast range of advanced life forms across its seas, lands, and skies. Earth's biodiversity is extensive, with an estimated 1.5 million cataloged species and potentially many more yet to be discovered.

Formation and Structure of Earth00:00:19

Approximately 4.5 billion years ago, Earth formed from particles left over from the sun's creation. Gravity drew these particles together to form the planet, which consists of a solid inner core, a liquid outer core, a mantle of flowing silicate rocks, and a rocky crust. Earth is the third planet from the sun, orbiting at an average distance of 93 million miles.

Earth's Unique Position and Water00:00:55

Earth's unique distance from the sun allows it to maintain liquid surface water, unlike colder gas giants or hotter planets like Mercury. This position allows water to exist in all its forms: liquid, ice, and gas. This liquid water is crucial for creating nutrient-rich soil, forming oceans and freshwater systems, and adding moisture to the atmosphere.