Full name: light day
Plural form: light days
Alternate spelling: lightday
Category type: length
Scale factor: 25902068371200
The SI base unit for length is the metre.
1 metre is equal to 3.86069554627E-14 light day.
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A light day (also written light-day) is a unit of length. It is defined as the distance light travels in an absolute vacuum in one day (of 86,400 seconds) or 25,902,068,371,200 metres (~26 Tm).
Note that this value is exact, since the metre is actually defined in terms of the speed of light. The light day isn't very frequently used at all since there are few astronomical objects or distances of that magnitude; the Oort cloud, for example, is thought to extend between 290 and 580 light-days out from the Sun.