Light year
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One light year is the distance that light travels in one Earth year.
It is approximately equal to 9.46 meters, or 5.88 12 miles.
Light years are common units of measurement used in starship navigation.
See also: Astronomical unit
Background
The exact length of a light year depends on the exact length used for one "Earth year."
The International Astronomical Union uses a Julian year of 365.25 days, while other sources may use a Gregorian year of 365.2425 days, or another year altogether.
| Source | year (days) | light year (meters) | light year (miles) |
|---|---|---|---|
| IAU | 365.25 | 9,460,730,472,580,800 | 5,878,625,373,184 |
| Gregorian | 365.2425 | 9,460,536,207,068,020 | 5,878,504,662,190 |
| 365.242199 | 9.460 528 4 | 5.878 499 81 | |
| Yahoo | 365.2411‡ | 9.460 5 | 5,878,482,164,161 |
