RL said:
"SO WHAT...? The 'zero' is only zero in respect to something else which is not zero, If I declare that 'zero' height is 20,000 feet above sea level nothing changes-"

My answer:
Well, lets see now, the absolute zero height would still be the center of the Earth and the number that we would consider as the constant or the reference zero would increase by 20,000, would you not consider that as a change?.

And this:
- "the thing is that the speed of light is a constant in ANY reference frame. The reason for this takes a lot more than your lazy attempts to comprehend..."

My answer:
My "lazy attempts to comprehend" have lead me to an understanding of why light is refracted by a lens. I hope that you understand it too.

From:
Http://homepage.sunrise.ch/homepage/schatzer/space-time.html

Minkowski Space-Time does not know any absolute time which is physically meaningful. It was the revolutionary idea of Albert Einstein to give the notion of simultaneity a new definition. Especially, because all experimental tests to determine the motion with respect to some absolute space-time frame had failed, he decided to abandon the notion of absolute time at all. In the famous theory of relativity he postulated two principles which should hold for all physics:
1) All physical laws appear according to the same laws in all reference frames.
2) The speed of light is constant in all reference frames.
Now, while the first postulate seems well established by observation and experiments, the second one is simply an assumption. It implies, in contrast to Galilean Space-Time, that simultaneity is not an absolute physical quality, but a relative one, depending on the motion of the observer (ie. the reference frame). <?blockquote>

From: http://csep10.phys.utk.edu/guidry/violence/lightspeed.html

To be precise, what we usually call the "speed of light" is really the speed of light in a vacuum (the absence of matter). In reality, the speed of light depends on the material that light moves through.

Johannes