Earth
Terrestrial Planet
Distance from Sun
149.6M km
About
Earth is the third planet from the Sun and the only known world to harbor life. Our home planet formed approximately 4.54 billion years ago and is the densest planet in the solar system. Its unique combination of liquid water on the surface, a protective magnetic field, and an oxygen-rich atmosphere creates conditions found nowhere else in the known universe.
About 71% of Earth's surface is covered by water, earning it the nickname "the Blue Planet." The remaining 29% consists of continents and islands. Earth's atmosphere extends about 480 km above the surface and is composed primarily of nitrogen (78%) and oxygen (21%), with trace amounts of argon, carbon dioxide, and other gases.
Earth's interior is divided into layers: a solid inner core of iron and nickel, a liquid outer core that generates our magnetic field, a thick silicate mantle, and a thin crust. The dynamic interaction between these layers drives plate tectonics, which continually reshapes the surface through earthquakes, volcanic activity, and the gradual movement of continents.
Key Facts
- Earth is the densest planet in the solar system, with an average density of 5.51 g/cm³.
- The planet's magnetic field, generated by its liquid iron outer core, extends tens of thousands of kilometers into space and shields life from harmful solar radiation.
- Earth is the only planet not named after a Greek or Roman deity — its name derives from Old English and Germanic words meaning "ground" or "soil."
- The Moon is slowly moving away from Earth at about 3.8 cm per year, and Earth's rotation is gradually slowing as a result.
- Earth's atmosphere protects us from about 99.999% of the Sun's harmful ultraviolet radiation.
- The deepest point on Earth's surface, the Mariana Trench, descends 10,994 meters below sea level — deeper than Mount Everest is tall.
- Earth's rotation speed at the equator is approximately 1,670 km/h, though we don't feel it because of inertia.
Exploration History
1957
Sputnik 1
First artificial satellite to orbit Earth, launched by the Soviet Union, marking the dawn of the Space Age.
1961
Vostok 1
Yuri Gagarin became the first human in space, completing a single orbit of Earth.
1968
Apollo 8
First crewed mission to orbit the Moon; captured the iconic "Earthrise" photograph.
1972
Landsat 1
First satellite dedicated to monitoring Earth's surface; started the longest-running Earth observation program.
1998–
International Space Station
Continuously inhabited orbital laboratory; humanity's permanent outpost in low Earth orbit for over 25 years.
Fun Fact
Earth is not a perfect sphere — it's an oblate spheroid, slightly flattened at the poles and bulging at the equator. The equatorial diameter is about 43 km greater than the polar diameter. If you shrank Earth to the size of a billiard ball, it would actually be smoother than one — even Mount Everest and the Mariana Trench would be imperceptible at that scale.