When the Speed of Light Becomes a Question

The article “Informational Renormalization of the Invariant Speed: A Causal–Symmetric Framework for Dynamical Light Propagation” asks a very simple but unsettling question:

What if the famous speed of light is not an untouchable, built-in constant of nature, but a visible symptom of a deeper informational state of the universe?

In everyday physics, space and time are taken as a given stage, and the speed of light is treated as a fixed number that structures everything else. In this work, that hierarchy is reversed. The paper builds on an informational framework in which the universe has something like an “informational conductivity”: a measure of how strongly past and future are linked by information. In earlier papers, this conductivity was used to explain the arrow of time (why there is a “before” and “after”) and how spacetime itself can emerge from informational relations. Now, the same structure is used to reconsider the status of the speed of light.

The central idea is this: instead of declaring the speed of light to be fundamentally fixed, the paper defines it operationally – as the speed that we actually measure using rods and clocks made of matter. But in this framework, matter and clocks themselves are influenced by the underlying informational dynamics. The work shows how one can introduce an information-dependent factor into the electromagnetic theory in a way that keeps all the usual symmetries and causal structure intact, yet makes the measured speed of light depend on the informational state of the universe. In a cosmological setting, this means that the effective speed of light is tied to the evolution of the universe’s informational conductivity, so that the flow of time, the geometry of space, and the numerical value of the invariant speed all come from the same underlying mechanism.

The paper then goes one step further. It shows that the very same informational structure can naturally define an additional “informational metric” with slightly wider light cones. Along these extended cones, a special informational field could, in principle, propagate faster than ordinary light. At first glance, this sounds like an invitation to time-travel paradoxes. But the framework contains its own safeguard: a global time ordering built from the informational conductivity. The paper formulates a clear condition that all such faster-than-light trajectories must respect, and under this condition no closed causal loops and no “grandfather paradoxes” can occur. Quantum nonlocality, as described in the earlier causal-symmetric work, remains non-signalling; any potential superluminal effects live in a separate informational sector and cannot be used to send messages into the past.

What makes this work distinctive is the unification it proposes. It does not just add another variable speed of light model on top of standard cosmology. Instead, it ties together four things that are usually treated separately: the arrow of time, the emergence of spacetime, the observed value of the speed of light, and the possibility of a controlled faster-than-light sector – all as different faces of a single informational law. In this way, the paper invites us to see the speed of light not as a rigid, unexplained input to the theory, but as an emergent property of how deeply the universe’s past and future are informationally connected.

You can find the full scientific article at:

Elias Rubenstein (2025): Informational Renormalization of the Invariant Speed: A Causal–Symmetric Framework for Dynamical Light Propagation
DOI: 10.5281/zenodo.17571615