Definition:Speed of Light/Value

Speed of Light: Value

The value of the speed of light in a vacuum is:

$\ds c$

$=$

$\ds 299 \, 792 \, 458$

$\mathrm {m \, s^{-1} }$

$\quad$ (exact)

$\ds $

$=$

$\ds 2 \cdotp 99792 \, 458 \times 10^{10}$

$\mathrm {cm \, s^{-1} }$

$\quad$ (exact)

The speed is smaller through a medium

It is customary in introductory material, or popular works on science, to use the approximation:

$\ds c$

$=$

$\ds 3 \times 10^8$

$\mathrm {m \, s^{-1} }$

1964: Milton Abramowitz and Irene A. Stegun: Handbook of Mathematical Functions ... (previous) ... (next): $2$. Physical Constants and Conversion Factors: Table $2.3$ Adjusted Values of Constants

who quote the historic $299 \, 792 \cdotp 50 \pm 0 \cdotp 10$, as that was what was contemporary on its publication.