SpaceAbout Moon
The Moon is Earth's only natural satellite. Earth and the Moon are tidally locked: their rotations are so in step that we only ever see one side of the Moon. Nobody saw the far side until a Soviet spacecraft flew past it in 1959. The Moon makes no light of its own. Moonlight is reflected sunlight.
Source: NASA, read on 12 November 2026.
Moon compared with Earth
Size. The Moon is 3,475 km across. That is 27% of the width of Earth (12,756 km). You would need about 3.7 of it in a row to match the width of Earth. Its mass is 0.012 times Earth's.
Gravity and your weight. Gravity at the surface is 1.6 m/s², against 9.8 on Earth. So things weigh 16% of what they do on Earth. Someone who weighs 50 kg on Earth would feel like 8.2 kg there. Try your own weight in the weight calculator.
Day. The Moon turns once on its axis in 27.3 Earth days. From one noon to the next, its day lasts 29.5 Earth days. The two figures differ because it also moves along its orbit while it spins.
Month. The Moon goes once round Earth in 27.3 days, measured against the stars. It lies on average 384,000 km from Earth, coming as close as 363,000 km and going as far as 406,000 km. Light takes 1.28 seconds to cross that gap.
Tilt and temperature. Its axis is tilted by 6.7°. The mean temperature in the fact sheet is −20 °C.
Moons, rings and magnetism. The Moon is itself a moon and has none of its own. Rings: no. A global magnetic field: no.
All the figures
| Diameter | 3,475 km |
|---|---|
| Mass | 0.073 × 10²⁴ kg |
| Density | 3,340 kg/m³ |
| Gravity | 1.6 m/s² |
| Escape velocity | 2.4 km/s |
| Rotation period | 655.7 hours |
| Length of day | 708.7 hours |
| Distance from Earth | 0.384 million km |
| Closest | 0.363 million km |
| Farthest | 0.406 million km |
| Orbital period | 27.3 days |
| Orbital velocity | 1 km/s |
| Orbital inclination | 5.1° |
| Orbital eccentricity | 0.055 |
| Tilt of axis | 6.7° |
| Mean temperature | −20 °C |
| Surface pressure | 0 bar |
| Moons | 0 |
| Rings | No |
| Global magnetic field | No |
Figures: NASA NSSDCA Planetary Fact Sheet, last updated by NASA on 18 March 2025, read on 12 November 2026. NASA rounds these values. Counts of moons change as new ones are confirmed.
Common questions
How big is Moon compared with Earth?
Moon is 3,475 km across, 0.27 times the diameter of Earth.
How long is a day on Moon?
From noon to noon, a day on Moon lasts 29.5 Earth days.
How many moons does Moon have?
The NASA fact sheet read on 12 November 2026 gives none.