What is the equation for calculating the speed of light in a vacuum?

Answer 1

The easy-to-use equation is: c = 299,792,458 m/s


The somewhat more detailed equation is:

c = the reciprocal of the square root of the product of

(the electrostatic permittivity of vacuum) x (the magnetic permeability of vacuum) .


I almost always use the first one.

Answer 2

It is not something that is calculated. In 1983 it was agreed by all the world's countries that the metre would in future be defined as the distance light travels in 1 second, and the number in the definition is 299,792,458 metres. This gets as close as possible to the old standard gold bar kept in a special room in Paris.

How do we know that won't ever change . . . . that's, as they say, a good question . . . . I suppose they check occasionally, just out of interest . . . .

Answer 3

foot and bubble