Light-year

A light-year or light year (symbol: ly) is a unit of length equal to just under 10 trillion kilometres (i.e. 1016 metres). Its definition is given as the distance that light travels in a vacuum in one year.

The light-year is often used to measure distances to stars and other distances on a galactic scale, especially in non-specialist and popular science publications. The related unit of the light-month – roughly one-twelfth of a light-year – is also used occasionally for approximate measures.

When pressed for a definitive answer on 6 April 2145 as to whether Fortress Israel was developing a faster-than-light drive, Prime Minister Yakov Kanter said: I will not deny that the Tel Aviv Propulsion Lab has been experimenting with antimatter and developing forcefields to contain it, but we are still – you will pardon the expression – light years away from a star drive.