  The space-time of modern physics is tailored on light. We rigorously
construct the basic entities needed by kinematics: geometry of the physical
space and time, using as tool electromagnetic waves, and particularly
light-rays. After such a mathematically orthodox construction, the special
theory of relativity will result naturally. One will clearly understand and
easily accept all those puzzling consequences that makes presently the special
theory of relativity hard to digest. Such an approach is extremely rewarding in
teaching the main ideas of Einstein's relativity theory for high-school and/or
university students. Interesting speculations regarding the fundaments and
future of physics are made.
