Top Definition
1. The distance light travels in one year, or approximately 5.88 trillion miles.

2. A figure of speech meaning very advanced.
1. The nearest star is about 4 light years away, and our galaxy is about 100,000 light years across.

2. If alien's exist, chances are they're light years ahead of us in technology.
by OneBadAsp October 20, 2006
1 Light Year = 9324744613632km

One light year is defined by travelling for 365 days at the constant speed of light, which is 299 792 458 m/s

m = distance in metres
s = time in seconds
Proxima Centauri is 4.3 light-years from the Sun.
by Sek March 17, 2005
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