Size and Distance

- Recall the Moon's diameter (3 500 km) and its approximate distance from Earth (380 000 km)


The Moon's diameter is 3476 km (that's approximately 3500 km).
It's about 25% of the size of the Earth. (Earth's diameter is 12,756 km.)

This is considered to be large for a satellite. Some astronomers regard the Earth and Moon as a 'double planet' similar to Pluto and Charon.

The average distance of the Moon from Earth is 384,000 km. That works out at about thirty Earth diameters away. You may also think of it as 10 Earth cirumferences away.

The moon takes 27.32 days to orbit once around the Earth. However, since the Earth is orbiting the Sun at the same time, the interval between two new moons is 29.53 days.



Why does the Sun appear to be the same size as the Moon (when viewed from Earth), when it is many times larger?


Mean distance of the Moon from Earth
384,400 km

Greatest distance of the Moon from Earth (Apogee)
406,740 km

Shortest distance of the Moon from Earth (Perigee)
356,410 km


NASA/Goddard Space Flight Center Measuring the Moon's Distance