⨁ Earth



Orbital radius

150 million km from the Sun (one astronomical unit, 1 AU)

Orbital period

365.26 days


12,800 km

Rotational period

23 hours 56 minutes (one sidereal day)




1g (by definition)


Earth has one moon, the Moon. It has a diameter of 3,500 km (just over a quarter the diameter of the Earth) and orbits at a distance of 380,000 km from the Earth. Proportionately this is much further than the major moons of the other planets: the Moon is about thirty Earth diameters away from the Earth, whereas Callisto (the outermost of the Galilean moons) is only thirteen Jupiter diameters away from Jupiter, and Titan (Saturn’s largest moon) is about ten Saturn diameters away from Saturn.

earth moon.png

The Moon is tidally locked to the Earth, meaning that we only ever see one side of it (left-hand picture). The opposite side is called the far side (right-hand picture). (The ‘dark side’ of the Moon is the side that is not currently being illuminated by the Sun. This varies constantly as the Moon rotates on its own axis.)

nearside and far side of the moon.jpg