Cosmic Queries – What is a Light Year?

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What is a light-year?

A light-year is a unit of length used to express astronomical distances, about 9 trillion kilometres, or 6 trillion miles. A light-year is the distance that light travels in vacuum in one Julian year, as defined by the International Astronomical Union. Because it includes the word “year”, the term light-year is sometimes misinterpreted as a unit of time.

Nigel is an internationally acclaimed science populariser and author, specialising in astronomy and space.

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