We propose a new picture of nature in which there are only two fundamental universal constantsè ē (≡e/c) andh(≡ħ/c). Our theory is developed within the framework of a new four-dimensional symmetry which is constructed on the basis of the Poincaré-Einstein principle of relativity for the laws of physics and the Newtonian concept of time. We obtain a new space-light transformation law, a velocity-addition law, and so on. In this symmetry scheme, the speed of light is constant and is completely relative. (...) The new theory is logically self-consistent, and it moreover is in agreement with all previously established experimental facts, such as the “lifetime dilatation” of unstable particles, the Michelson-Morley experiment, etc. There is a difference relative to the usual theory, though, in that our theory predicts a new law for the Dopplerfrequency shift, which can be tested experimentally by measuring the second-order frequency shift. (shrink)