# Speed of light

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## Definition

The Speed of Light (or c) is the speed at which a photon (an "energy packet" of electromagnetic radiation) travels in a vacuum.

### Values

The exact measurement for the speed of light is 299,792,458 meters per second, in the following values, the speed of light will use values based on the rounded 300,000,000 m/s.

Meters per second:

$\displaystyle c = 3 \times 10^{8} \mathrm{m s^{-1}}$

Kilometers per second:

$\displaystyle c = 3 \times 10^{5} \mathrm{km s^{-1}}$

Miles per second:

$\displaystyle c = 1.9 \times 10^{5} \mathrm{mi s^{-1}}$