OT question
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?
The electromagnetic behaviour of space is described by Maxwell's
Equations. As newshound has suggested, it is possible to show* that a
wave equation is a possible solution of Maxwell's Equations, and that
the speed of the resulting wave would be equal to ...
1 / sqroot( permittivity of space * permeability of space)
.... and that this value is exactly equal to the measured speed of light
in space. This is how we know that light is an electromagnetic wave.
* This is science speak:
It is trivial to show that = an undergrad can prove it
It is easy to show that = a postgrad can prove it
It may be proved that = The prof can prove it
In this particular case, I was able to prove it at uni, and did so
during a physics tutorial, which, I discovered much later from a
busstop conversation between another student who'd been present with my
then girlfriend, gave me something of a reputation for the subject.
But I wouldn't want to be asked to prove it now!
