Guide Note

Earth is the third planet from the sun and is the largest of the inner planets in the solar system in both diameter and mass. The only planet in the Universe on which life is known to exist, Earth is home to millions of species, including at least one sentient life form, Homo sapiens sapiens.

At the center of the Earth is a solid iron core, surrounded by magnetic liquid and a thick layer of mantle.

Fast Facts

1. Also Known As: Gaea, The World, The Big Blue Marble, Terra
2. Age: 4.54 BYA (approximate)
3. Mean Diameter: 7,926 Miles
4. Mean Circumference: 24,880.616 miles
5. Surface Land Area: 92,547,025.4 square miles
6. Surface Water Area: 224,394,021 square miles
7. Mass: 6.59182164 ²¹ tons
8. Escape Velocity: 6.95065816 miles per second
9. Atmospheric Composition:
   1. Nitrogen: 78.08%
   2. Oxygen: 20.95%
   3. Argon: 0.93%
   4. Carbon Dioxide: 0.038
   5. Trace elements and compounds
10. Mean Distance from the sun: 93 million miles
11. Orbital Period: 365.256366 days
12. Orbital Eccentricity: 0.016710219
13. Axial Inclination: 23.439281°

About 71% of Earth's surface is covered in liquid water, mostly in the form of oceans. These seas not only help drive the atmosphere, they lubricate the crust of the planet, enabling the motion of tectonic plates. The movement of the plates constantly recycles the mineral and biological material available on the planet and in turn, shapes climate and makes ecosystems possible.

Earth has one natural satellite, the moon, also known as Luna. This large satellite is believed to have been created from accreted orbital ejecta from the collision with Earth of a small planetoid early in the history of the solar system. The moon's gravity has attracted asteroids, comets, and meteors to its surface than may have otherwise struck Earth.