Written entirely from an untutored viewpoint, this essay can only very tentatively venture some thoughts about a concept that very much belongs to the discipline of physics. This is the classical notion of naturally-moving reference systems; a concept central to thought experiments published a century ago, by Albert Einstein. A critical reading of one of these original accounts forms a springboard for detailed discussions; eventually they give rise to an argument for re-appraising the reference system concept. In the account in question, Einstein famously uses an imaginary train struck by lightning to illustrate his reasoning for the relativity of simultaneity. It seems this argument has been received with a widespread and almost unanimous approval, over the years. Yet it’s equally apparent that Einstein’s argument drew solely on classical mechanics; and it’s troubling that in preferring this simple logic, he allowed it to contradict the predictive force of his own famous postulates. So a sort of remedial analysis was undertaken: it accepted his postulates and applied them to the train scenario, independently of the classical transformation he chose. It is shown how this meticulous reanalysis leads unambiguously to the conclusion, not that simultaneity is relative, but that simuitaneity is conserved. Evaluating what to make of this disparate outcome leads to pursuing its resolution in much more philosophical terms. First, a review portrays how theoretical physicists’ views on the status of space have radically evolved over the last century. Adopting and adapting their current understanding, it’s suggested how naturally-moving systems might be newly characterised, not only in the old sense, by a spatial framework of material bodies, all moving uniformly in unison, but also by an additional content of equally co-moving segments of spatial field — areas which hitherto were seen only as abstractions from a stationary and homogenous background of empty space, through which the framework of matter moved. From the much newer perspective, these additional co-moving frame contents have highly dynamic substance. Taken together across multiple moving frames, they constitute super-plastic and holistically extended dynamic fields — such as electric and magnetic fields. On this speculative basis it’s explained how light waves would indeed show a constant ‘vacuum’ velocity in all frames, just as Einstein and Maxwell required — but would also be Galilean in nature, just like sound. A recent report of measurements directly supporting the reality of a Galilean view of light is cited.