Moon
Earth's Celestial Companion
The Moon is Earth's only natural satellite and the fifth-largest moon in the solar system. It is the only celestial body beyond Earth that humans have visited. The Moon's gravitational pull creates tides on Earth and it is slowly moving away from our planet.
Key Facts About the Moon
- Diameter: 3,474 km (2,159 miles)
- Distance from Earth: 384,400 km (238,855 miles)
- Day length: 29.5 Earth days
- Surface Temperature: -173°C to 127°C
- Atmosphere: None (trace exosphere)
- Water: Ice at poles and subsurface
Apollo Missions
Between 1969 and 1972, NASA's Apollo program landed 12 astronauts on the Moon across six missions. The first person to walk on the Moon was Neil Armstrong during Apollo 11 on July 20, 1969.
Lunar Phases
The Moon goes through eight phases as it orbits Earth, from new moon to full moon and back. These phases are caused by the changing angle between the Sun, Earth, and Moon. A complete lunar cycle takes about 29.5 days.