Approaches of Experimental Designs to test Light Speed Invariance to Observers*

The principle of the constancy of the velocity of light, which stated that the light velocity is invariant to the motion of the emitter, was well established and proven by many experiments. Interestingly, the further assumption that the light velocity is also independent of the motion of the observer was, arguably, never proven conclusively by any experiment for more than a century. Since this is a key assumption of some fundamental physical theory, it created a century-old theoretic gap. The difficulty cited for designing such experiments is mostly referred to the concerns of time synchronization and time dilation during the measurement. This paper proposed an innovative approach that will mirror the same approach of testing the light-speed invariance to the emitters, i.e. directly test the synchrocity of the light traveling as to multiple moving sensors. By leveraging the well-established light-speed invariance to moving emitters as the reference alignment, the experiment is designed in such a way that the concerns of time synchronization and dilation can be avoided. Other approaches are also proposed, for example, the improvement of first approach by directly measuring light travel time with an interferometer; and testing the isotropy of the light speed  by measuring the “relativistic mass”, i.e. the inertia, of two high-speed particles moving at the same speed but in different directions. The experiment results, if positive, will conclusively close a century-old theoretic gap. Otherwise, it may imply a need for further investigation of the light-speed invariance to moving observers. For example, the Asymmetry Theory made its predictions of results for these experiments. Either way, the design and execution of these experiments will have significant importance.