Atlas · Earth
The Moon’s orbit
The Earth has one moon, and it is a large one: more than a quarter of the Earth’s width. It goes round once in 27.3 days, about thirty Earth-widths away.
The Earth and the Moon
The Earth and the Moon’s path, to scale, seen from above the plane of the planets. The gap really is this wide: all the other planets would fit side by side between the two.
The edge of the drawing is 430,000 km from the centre of Earth.
How to read it
You are looking straight down on the plane of the planets, from its north side. Earth is drawn to scale with the orbits. The moons are not: at this scale most would be far too small to see, so each is a dot.
The Sun pulls on the Moon almost as hard as the Earth does, so its path is not a fixed ellipse. The line is the Moon’s real track for the two weeks either side of today, which is why it does not quite close on itself.
- Solid dot. A spacecraft has mapped the whole surface.
- Half dot. A spacecraft has seen part of it.
- Ring. Never seen as more than a point of light.
- Pale line. Goes round the usual way, the way the planets go round the Sun: anticlockwise on these drawings.
The orbit is a slowly turning ellipse fitted to positions from NASA’s Jet Propulsion Laboratory for the years 2000 to 2040. The list gives how far out each fit can be. Touch a row to pick out its orbit.
The Moon
1 moon
The only world beyond the Earth that people have walked on.
| Moon | Orbit size | One orbit | Tilt | Width | Found | See it in 3D |
|---|---|---|---|---|---|---|
| The Moon. Mapped by spacecraft.drawn to within 0.01° | 384,400 km | 27.32 days | 5.2° | 3,475 km | Fly there |
Where this comes from
- Jean Meeus, Astronomical Algorithms, chapter 47 (the lunar theory used here), checked against JPL Horizons
- NASA, Moon facts
Orbit size is the average distance from the centre of Earth. Tilt is measured from Earth’s equator for the close moons and from the plane of the planets for the far ones, and above 90° means the moon goes round backwards.