# There is only one speed

Zvonimir Šikić

*Faculty of Mechanical Engineering and Naval Architecture, University of Zagreb*

AbstractMinkowski developed the four-dimensional physical space by combining three space coordinates and a time coordinate into a four-dimensional event and hereby: „Space by itself and time by itself are doomed to fade away into mere shadows, and only a kind of union of the two will preserve an independent reality.“ Einstein joked that he no longer understood the special relativity (since the mathematicians took it up) but it is clear that the new geometric perspective was a great advance. It enabled Epstein to conclude that everything moves with the speed of light in this four-dimensional space-time: “The reason you can't go faster than the speed of light is that you can't go slower.There is only one speed.Everything, including you, is always moving at the speed of light.” We will explain the philosophy of these extraordinary assertions.