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A megametre (American spelling: megameter) (symbol: Mm) is a unit of length equal to 106 metres. Its customary equivalent is 621.37 miles.
Megametres are rarely seen in practical use, because they are too big for most terrestrial tasks. They can also be easily confused with millimetres (mm). Still there are a number of "megametre fans". Megametres are also occasionally found in science fiction.
See also: square megametre, cubic megametre, 1 E6 m, SI, metre, SI prefix, Orders of magnitude, light year, parsec
kilometre << megametre << gigametre
A megameter is also a type of astrometrical instrument used for determining longitude by observation of the stars.