On 24/12/2017 20:43, Bill Wright wrote:
What are the parameters that set the speed of electromagnetic
transmission in a vacuum? I've googled everywhere but I can't find the
answer. It's easy enough to find the figure but WHY? Why not
29,979,245.8 metres per second or 2,997,924,580 metres per second?

Bill

You have to bear in mind that the metre is an arbitrary distance based
on the circumference of the Earth, and a second was a fraction of the
duration of the Earth's orbit, finally fixed as a number that is
9,192,631,770 cycles of the radiation produced by the transition between
two levels of the caesium 133 atom.

Admittedly we have got nothing better to describe the speed of light,
but it does explain why that speed when calculated isn't a conveniently
memorable number.

Jim