# Light second

From Citizendium, the Citizens' Compendium

The **light second** is the distance that the light travels in vacuum in one second and so is a unit of distance.

Similar units are the light minute, light hour, light day, light week, light month, light year.

### Numerical value

As opposed to the light year, whose value more or less depends on the definition of year, the value of the light second is defined exactly.

- velocity of light in vacuum: 299,792,458 m/s
^{[1]}(meters/second) - 1 light second = 299,792,458 m = 2.99792458 * 10
^{8}m

### Comparison to other Units

- 1 AU = 499 light seconds
- 1 light second = 299,792.458 km
- 1 light second = 186,282.397 mi
^{[2]} - 1 light second = 983,571,056.4 ft
^{[3]} - 1 light second = 327,857,018.8 yd
^{[4]}

### Distances in Light Seconds

- the maximum distance between earth and moon is about 1.3 light seconds
- the maximum distance between earth and sun is about 499 light seconds or 8.3 light minutes

### Notes

- ↑ Review of Particle Physics
Particle Data Group: W.-M. Yao
*et al.*, J. Phys. G 33, 1 (2006). - ↑ 1 mi = 1609.344 m
- ↑ 1 ft = 0.3048 m
- ↑ 1 yd = 0.9144 m