|
|
|
|
|
|
The light-second 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 onesecond, and is equal to exactly 299792458 metres (just over 186282 miles).
A league is a unit of length (or, in various regions, area). It was common in Europe and Latin America, but is no longer an official unit in any nation. The word originally meant the distance a person could walk in an hour. Since the Middle Ages, many values have been specified in several countries.