First point: "The derivative of a constant is zero."

No kidding! Wow... You do know your mathematics!!! You probably searched on the internet for hours to learn that fact... (I assume this since you have shown in the past that you have no grasp of basic math, such as multiplication)

The speed of light is considered as a constant therefore its derivative is zero.

AGAIN WOW!!!! ... There are an INFINITE number of other constants that have a derivative that is zero... like 1,2,e,3,PI and 4.1423544274464728894004577743252644552431537489050564289214355.... SO WHAT?!

You are a twit, Johannes- You are too lazy to learn the language of science so you pick words at random and regurgitate them... you make a fool of yourself in the process.

The zero is used in many situations as a point of reference, such as, the zero point in the temperature scale either in Fahrenheit or Celsius indicates a condition of the heat content. The actual temperature can go above or below this reference point.

Oh, I see- you think semantics equals science... GREAT... science based on definitions looked up on the internet- that will go far.

We can also consider the water level of the worlds oceans as a reference point and call that zero height, but we can go above or below that zero reference height. We could also calculate the mean distance from the center of the Earth to the water surface of the oceans and then we could call that distance a constant because the distance does not vary very much from year to year.

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- 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...

Look, you are a fairly stupid, stubborn, loon with a psychological problem... If you WANT to learn about the way the way things work you need to lose at least 2 of those 4 conditions... The thing is you have demonstrated over and over that you dont want to learn... You just want a stage to spout your garbage. The Space board is NOT the place- hell, the pre meds I taught had more common sense than you express here.

I think you are used to talking to people that are equally ignorant- and you foolishly think you can get away with it here... my suggestion is you stick with your ignorant friends or get an education... my guess is you will do the former...