Just as periodicity form the basis of our concept of time, so light has been the basis of our rectilinear concept of space. We notice how diverse circumstances like refraction and diffraction deviate light and so we contrive to diminish the influence of such effects as far as is physically possible in order to then use the protected light-transmission phenomena as a reference for what is rectilinear. Ultimately, we determine the straightness of a physical thing by comparing it with the transmission of light that has been protected from those influences which are known to alter its path. If the transmission of light is influenced by gravity, then consideration needs to be given as to how this effect can be compensated for when other phenomena are being investigated with respect to an assumed rectilinear system of axes. For most terrestrial situations such as surveying, such considerations may be of no great significance, but for astronomical situations, supposing space to be curved for some theoretical purpose is to ignore the reality that it is light that is the present ultimate reference of straightness.
Since the nature of the observable universe is that of chaotic interactions, within which broad general phenomena evolve and sustain a temporary equilibrium, one could expect that light might be no different. Certainly it interacts with objects in the universe and is itself perturbed by refractions, polarizations, absorptions and the like, so there is no immediate persuasion to confer special status. Because of the infinitely multiple complexities of the turbulent universe, any descriptions of any particular phenomena within it...be it a tree, a flash of lightning, or a psychiatric disorder...will always be a grossly approximate simplification of the phenomena. It is simply a pragmatic strategy therefore, neither to expect light to be a phenomenon of atypical cosmic participation, nor to be able to acquire an unambiguous absolutely definitive simplified description of its nature. We should expect therefore, that such observable light characteristics as photons and waves would behave in a comparable manner to similar cosmic phenomena.

In a universe where nothing remains the same, to postulate that in certain theoretic circumstances, the velocity of light is constant, is to fly in the face of the experiences of reality. Waves and pulse-like phenomena attenuate. Objects are restrained by the medium thru which they travel. Supposing there to be a hypothetic free space, devoid of influence, is an existential impossibility. What has been called empty space has never been so, whether it is that between the galaxies, between the stars, between atoms, or between any of the words on this page. Any location in the universe has always been constantly awash with innumerable wave-photons and diverse particles all randomly heading towards the next stage of their existence. So-called space therefore is a chaotic flux of entities, participating with and transmuting from and into some form of cosmic mass-fabric which can sustain the transmission of individual tympanic-like stress-pulse dimples. If mass is a form of energy and electromagnetic phenomena are energetic phenomena, then space, being an intrinsic part of the universe, would also seem to be able to be described as being a form of mass-media.