A light-year is a unit of distance measurement based on the travel of light energy, undisturbed in a vacuum, over the course of one Earth year.
History and specifics[edit | edit source]
A light year is about 9.5 quadrillion meters long.
Appendices[edit | edit source]
References[edit | edit source]
- …
External link[edit | edit source]
- Light-year article at Wikipedia, the free encyclopedia.
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