Moon facts

Moon facts

How big is the Moon

3,474 km across
Its mean radius is 1,737.4 km, so it is about 3,474 km wide: 27% of Earth's width, a little over a quarter.

How old is the Moon

About 4.5 billion years
It formed soon after Earth, most likely from debris thrown into orbit when a Mars-sized body struck the young Earth.

Moon temperature

From 127 °C to −173 °C
With almost no atmosphere to hold heat, the surface reaches about 127 °C at lunar noon and falls to about −173 °C at night.

Moon gravity

1.62 m/s²
That is 16.5% of Earth's, about one sixth: a 70 kg person weighs 113 newtons on the Moon against 686 on Earth. Work out your Moon weight.

Distance from Earth

384,400 km on average
The orbit is slightly oval, so the distance runs from about 356,400 km at the closest point to about 406,700 km at the farthest. Light takes about 1.3 seconds to cross it. Distance today.

Why we see the same side

It turns once per orbit
The Moon spins once on its axis in the same 27.3 days it takes to orbit Earth, so the near side always faces us. A slow rocking called libration shows about 59% of the surface over time. Libration by date.

The far side of the Moon

Not permanently dark
The far side has day and night like the near side. It is the side that never faces Earth, and it has far fewer dark lava plains than the face we see.

Orbit and phases

27.3 days to orbit, 29.5 days for the phases
The phase cycle is longer than the orbit against the stars because Earth moves around the Sun while the Moon moves around Earth.

NASA Moon facts lists physical properties and orbital context.