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- Dictionarylight year/ˈlʌɪt jɪə/
noun
- 1. a unit of astronomical distance equivalent to the distance that light travels in one year, which is 9.4607 × 1012 km (nearly 6 million million miles).
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- light-year
Unit of astronomical length, defined as the distance that light travels in the vacuum in one year
A light-year, alternatively spelled light year, is a unit of length used to express astronomical distances and is equal to exactly 9460730472580.8 km, which is approximately 5.88 trillion mi. As defined by the International Astronomical Union (IAU), a light-year is the distance that light travels in vacuum in one Julian year (365.25 days). Despite its inclusion of the word "year", the term should ... Wikipedia
