The speed of light constant in all reference frames?

If the formula of an object's speed relative to another object is:


(v + u) / (1 + vu/c²)


v being the first object's speed


u being the second object's speed





This means that if an object is traveling at the speed of light, it will travel at c relative to any object. This shows that light is constant in every reference frame. But, does this also mean that light that has been slowed down (because of the medium it's in) is NOT constant in every reference frame? If you do the math with v being light slowed down and u being an object, at any speed, then the relative speed would not be 299,792,458 m/s.

The speed of light constant in all reference frames?
yes it is constant in all reference frames...





as for the experiment where it is slowed down, the speed that is seen during that experiment would be witnessed by everyone regardless of if they were going .00000005 meters per second


or or 100,000 meters per second.....
Reply:I always figured when they say slowed down, they really mean that the light is not taking a direct path. (or is encountering gravitational wells or other temporal distortions)