Earth

Positioned perfectly in the habitable zone, Earth is a complex system of life, climate, and geology.

Telescopic picture of planet Earth

Introduction

Earth is the only planet in the solar system with a name that is not derived from Greek or Roman mythological nomenclature. Instead, "Earth" is a loan from Old English and Germanic languages for "ground" or "soil." The name has been in place for over 1,000 years, while other planets—like Mars, Venus, and Jupiter—are named after mythological gods and goddesses.

A Unique World of Life

Earth is the single planet known to harbor life. One of its main reasons for this is that it has liquid water on its surface—comprising almost 70% of the planet. Due to Earth's perfectly suitable temperature and chemical makeup, life emerged in its oceans around 3.8 billion years ago and has diversified into a variety of forms. However, the ability of Earth to sustain life is being threatened by climate change, which is altering critical systems like weather and sea level.

Properties

Property	Information
Size and distance from the Sun	Earth is the biggest rocky planet, slightly bigger than Venus. It is approximately 12,760 km (7,926 miles) in diameter. Earth is 150 million kilometers (93 million miles) from the Sun—1 astronomical unit (AU). Sunlight travels to our planet in about 8 minutes.
Rotation, orbit and seasons	The planet rotates once on its axis in 23.9 hours, creating day and night. It requires 365.25 days to make one orbit around the Sun, hence the requirement for a leap year every four years. The planetary axis is tilted at 23.4°, hence the formation of seasons:   When the Northern Hemisphere is facing towards the Sun, it's summer,   and the Southern Hemisphere is in winter, and vice versa. In spring and autumn, the two hemispheres receive equal amounts of sunlight.
Moon	Earth possesses a single satellite by nature—the Moon, which is significant to Earth's world. The Moon maintains Earth's axial tilt, controlling variation in seasons. It likely stemmed from an enormous collision between early Earth and another object. The Moon is 384,400 km away and is the solar system's fifth-largest moon. Earth's gravity occasionally snares transient mini-moons, tiny asteroids briefly orbiting Earth.
Rings	Unlike the Moon (Saturn or Jupiter) or gas giants, Earth's Moon has no rings.

Formation

Earth is believed to have been created around 4.5 billion years ago when gravity consolidated dust and gas into a planet. It differentiated over time into layers: metallic core, rocky mantle, and solid crust.

Inner Structure

Earth is composed of four general layers:

• Inner Core – solid iron and nickel, radius ~1,221 km, up to 5,400°C temperatures

• Outer Core – liquid metal, ~2,300 km thick, generates Earth's magnetic field

• Mantle – ~2,900 km thick, composed of hot, slowly moving rock

• Crust – the outside cover, up to 30 km thick on land and 5 km under seas

Structure Features

The Earth has volcanoes, mountains, valleys, and ocean basins.

• Its crust is broken into tectonic plates that slowly move:

• This movement produces earthquakes, volcanic eruptions, and mountain range creation.

• The Mid-Ocean Ridge—the longest mountain range in the world—is under the ocean and four times longer than the Andes, Rockies, and Himalayas combined.

• The ocean is 4 km (2.5 miles) deep on average and contains 97% of the Earth's water.

Atmosphere

The Earth's atmosphere contains:

• 78% nitrogen

• 21% oxygen

• 1% trace gases (argon, carbon dioxide, etc.)

It serves several critical functions:

• Controls temperature

• Protects against solar radiation

• Burns up incoming meteoroids, which flash across the sky like shooting stars

Magnetosphere

The Earth's spinning liquid outer core generates a magnetic field that protects the planet from the solar wind (a stream of charged particles from the Sun). The magnetic field is teardrop-shaped and repels harmful particles.

When the particles strike gases in the region near the poles, they create glowing lights named auroras—the Northern and Southern Lights.

Earth's magnetic field periodically reverses (magnetic north to magnetic south), roughly every 400,000 years. Such transitions do not injure living organisms but potentially short-term confuse navigation systems.

Scientific diagram of Earth

Summary

Earth is the only known planet that supports life, thanks to its liquid water, protective atmosphere, and perfect distance from the Sun. It rotates every 24 hours and orbits the Sun in 365.25 days, giving us day, night, and seasons. Earth's structure includes a solid inner core, liquid outer core (which creates a magnetic field), mantle, and crust. Its surface has mountains, oceans, and moving tectonic plates that cause earthquakes and volcanoes. The atmosphere, mostly nitrogen and oxygen, regulates temperature and blocks harmful radiation. Earth has one large Moon that helps stabilize its tilt and seasons, and no rings. It formed about 4.5 billion years ago from gas and dust.