Earth

Earth is the third planet from the Sun and the only world known to support life. Covered by vast oceans, drifting clouds, and diverse ecosystems, it is a dynamic planet shaped by geology, climate, and life over billions of years.

From space, Earth appears as a bright blue world wrapped in a thin atmosphere—an oasis of liquid water and life in the darkness of space.

A Planet That Supports Life

Earth formed about 4.5 billion years ago. It is the largest rocky planet in the Solar System and the only known world with stable liquid water across its surface. More than 70% of Earth is covered by oceans.

Liquid water, a protective atmosphere, moderate temperatures, a stable orbit, and a magnetic field all help create conditions in which life can survive and evolve. Scientists are still studying how these factors combined to allow life to begin on Earth.

Atmosphere and Climate

Earth's atmosphere is made mostly of nitrogen and oxygen. This thin layer supports weather and the water cycle, helps regulate temperature, and contains ozone, which absorbs much of the Sun's harmful ultraviolet radiation.

The natural greenhouse effect traps enough heat to keep much of Earth's water liquid. Without it, the planet would be far colder and less suitable for life as we know it.

A Dynamic Surface

Earth's surface is constantly changing. Plate tectonics slowly move continents, build mountains, cause earthquakes, and drive volcanic activity. Wind, rain, ice, and rivers reshape landscapes through weathering and erosion.

Key Facts About Earth

Diameter: About 7,918 miles (12,742 kilometers)
Average Distance from the Sun: About 93 million miles (1 AU)
Day Length: About 24 hours
Year Length: About 365.25 days
Average Surface Temperature: About 59°F (15°C)

The Water Cycle

Earth has a global water cycle that continually moves water between oceans, the atmosphere, clouds, rivers, lakes, ice, soil, and groundwater. Water evaporates, condenses into clouds, falls as precipitation, and eventually returns to the oceans.

The Moon and Tides

Earth's Moon pulls on the oceans and helps create tides. It also contributes to the long-term stability of Earth's axial tilt, which influences the planet's seasons and climate.

Earth’s Magnetic Field

Movement within Earth's liquid iron outer core generates a magnetic field. This field deflects many charged particles carried by the solar wind and helps protect Earth's atmosphere and surface environment.

Seasons and Orbit

Earth's axis is tilted by about 23.5 degrees. As the planet orbits the Sun, this tilt causes each hemisphere to receive different amounts of sunlight at different times of year, creating the seasons.

Our Home in Space

Earth is humanity's home and the only place where life is currently known to exist. Seen from space, it highlights the importance of understanding and protecting the environment that makes life possible.