If the spacetime angle (α) is maximal (π/2 or 90°), this is an extreme (at limit) motion. An object moves with (maximum) speed together with time and as the object has “caught” time in this case, motion within spacetime is completely in its longitudinal element, while the time element is zero!
While external terrestrial observers will observe the flight of our light beam (in their external optics, we will fly at the speed of light) to a distance of millions of light-years (generations of scientists will spend millions of years at an observatory), we would not be able to even blink with our eyes when standing “on board” and we will reach the destination. The time of our flight will be zero. Speed from our point of view will be infinite as well as the infinite tangent of a right angle! More on www.timetheory.net