If Rest Is Impossible, then the Speed Must Not Depend on the Observer

Only regular curves have a well-defined curvature. As the rest implies the appearance of singular points, it results that in the rest the curvature is indefinite. So rest is impossible. Due to the fact that rest is impossible, it follows that the speed must be independent of the observer. I have already argued on several occasions why rest is impossible. I remind you of these arguments in more detail now, and I will draw clearer conclusions from them.