The Moon

Earth's anchor

Vital statistics

• Mean radius: 1,737 kilometres
• Mass: 7.34 × 10²² kilograms
• Surface gravity: 1.62 metres per second squared
• Sidereal rotation: 27 days
• Orbital period: 27 days
• Mean temperature: -20 °C
• Axial tilt: 6.68 degrees

Field notes

• The Moon is drifting away from Earth at 3.8 cm per year — about the rate your fingernails grow. Total solar eclipses are a temporary cosmic coincidence.
• Moonquakes are real, and with no water to dampen the shaking, the Moon 'rings like a bell' — Apollo seismometers watched it vibrate for nearly an hour.
• There is no permanent dark side. The far side gets just as much sunlight — two weeks of day, two weeks of night — we simply never see it from Earth.
• Twelve people have walked on it. With no wind or rain, their bootprints could survive for millions of years.

Data: NASA Planetary Fact Sheets. Explore the full interactive 3D map at the home page — every orbit is computed from real Keplerian elements.