Why is light at a constant speed

[swansont]

the speed of light "changes" then in a cyclic fashion? I was referring to the measurement of the speed of light.

 

So the speed of light actually does change depending on the observer is that it?

 

The speed of light is the same for any inertial observer. Anyone contending anything to the contrary really has to provide support for their position for it to be considered.

 

And I reread things, yes, Mowgli suggested cyclic measurements, but gave no data to support that hypothesis.

[John Cuthber]

Incidentally, the current definition of the metre (since 1983) means that the speed of light (in vacuo) is constant by definition.

http://www.bipm.fr/en/si/history-si/evolution_metre.html