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# moon's mean radius

The Moon's mean radius is, as it is for planetary objects like the Earth, determined as the average distance from the physical center to the surface. The value, symbolized r moon , is equal to approximately 1,738,000 meter s (1.738 x 10 6 m). This is roughly 1,738 kilometer s (km) or 1,080 statute mile s.

The Moon is not a perfect sphere; its shape is slightly distorted because of tidal effects caused by the gravitation of the Earth. In addition, there are irregularities in the surface because of craters and mountains. The actual lunar radius varies slightly depending on the direction in which it is measured. The mean radius is obtained from a large number of individual measurements in various directions.

Based on the value of r moon given here, the volume of the Moon ( V moon ), in meters cubed (m 3 ), can be found using the standard formula for the volume V of a sphere in terms of its radius r :

V = (4/3)(pi) r 3

where pi represents the ratio of the circumference of a circle to its diameter, an irrational number equal to approximately 3.14159. Based on this formula:

V moon = 2.199 x 10 19 m 3

Also see Table of Physical Units and Constants.

This was last updated in February 2008
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