It's best to separate two elements here -- the measured speed of light, and the relationship between space and time. The relationship between space and time is

It's best to separate two elements here -- the measured speed of light, and the relationship between space and time. The relationship between space and time is easily expressed in closed form: t' = t √(1-v^2/c^2) That's pretty clear and easy to interpret. So measurements of c may be messy and subject to controversy, but the geometry expressed in the above equation, and what it tells us about spacetime, is much more clear.