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The light-hour is a unit of length useful in astronomy, telecommunications and relativistic physics. It is defined as the distance that light travels in free space in onehour, and is equal to exactly 1.0792528488×1012 metres.
A cable length or length of cable is a nautical unit of measure equal to one tenth of a nautical mile or approximately 100 fathoms. The unit is named after the length of a ship's anchor cable in the Age of Sail. The definition varies: