Let's call "ideal" space a xyz-space where is no limit for speed. "Real" space is the xyz-space with maximum speed c. Now, the speed c in real space is in many ways similar to infinite speed in ideal space: 1. ideal: infinite speed is always observed as infinite, regardless the observer's (finite speed) motion real: speed c is constant to all observers 2. i: finite speeds are never constant, but relative r: sub-c speeds are relative 3. i: finite speeds can be added, and the results is always finite r: sub-c speeds can be added (in certain way), and the result is always below c 4. i: if infinite speed is added to a finite speed, the result is infinite r: if speed c is added to a sub-c speed, the result is c (light emitting by moving particle) 5. i: no particle with mass can have infinite speed (it would have infinite kinetic energy) r: no particle with mass can have speed c 6. i: kinetic energy of a particle can be arbitrarily large, with large enough speed r: kinetic energy of a particle can be arbitratily large, with speed close enough to c 7. i: for any finite distance, the travelling time can be arbitrarily short with large enough speed r: for any finite distance, the travelling time can be arbitrarily short with speed close enough to c This is a short list, maybe it could be longer. Anyway, I think I made my point clear. The light speed c has many, most or maybe all the qualities of infinite speed, without actually being infinite. I have very much difficulty to understand (and accept) the light speed as a universal constant and an upper limit for speed. Of course I'm convinced it's true, but I can't help this. Do you think it's of any use to seek this kind of analogies? Or should we go with "just the facts"? By the way: Does a wave of light (a photon in vacuum) have a reference frame? What would be actually observed there?