Measuring velocities requires the synchronization of spatially-separated clocks. Because this synchronization must precede the determination of velocities, no system of clock synchronization--such as that based on Einstein's presumption of light-speed isotropy--can ever be founded on an experimentally-validated velocity. I argue that this very old observation, which lingers in the philosophical literature under the heading ``Conventionality of Synchronization,'' suggests an explanation of why ``spooky'' quantum correlations can transfer no information at any speed, superluminal or otherwise. This work constitutes the first application of the Conventionality doctrine outside of Relativity itself.
Measuring velocities requires the synchronization of spatially-separated clocks. Because this synchronization must precede the determination of velocities, no system of clock synchronization--such as that based on Einstein's presumption of light-speed isotropy--can ever be founded on an experimentally-validated velocity. I argue that this very old observation, which lingers in the philosophical literature under the heading Conventionality of Synchronization,'' suggests an explanation of why spooky'' quantum correlations can transfer no information at any speed, superluminal or otherwise. This work constitutes the first application of the Conventionality doctrine outside of Relativity itself.
One of the main issues in measuring the speed of light when it only travels from one spatial position into another position, known as the one-way speed of light, is that the clocks belonging to each separated spatial position are not and, in principle, cannot be synchronized. Here, we show that it is possible, in principle, to measure the velocity of particles that travel at the speed of light without assuming a round-trip once we adopt a quantum mechanical description under two boundary conditions to the state of the quantum system followed by the two-state-vector formalism while assuming non-synchronized quantum clocks with unknown time dilation. The weak value of velocity can be measured for a test particle that has a clock that is not synchronized with the clock of the quantum particle. Following the proposed set-up, when the weak value of the velocity is known even without knowing the time states of the system, such a weak velocity is the two-way speed of light. We further explore some fundamental implications of the set-up. The proposed approach opens a new avenue toward measuring the velocities of quantum particles while overcoming relativistic issues regarding the synchronization of clocks.
This paper advances the core thesis that the speed of light is the limit of physical quantities, not the limit of spacetime quantities. The "superluminal" correlations of quantum entanglement and the "superluminal" recession of distant galaxies in cosmic expansion are not violations of relativity, but rather because these two phenomena belong to the category of spacetime quantities and fall outside the jurisdiction of the speed of light. Through the methodology of "hierarchical reclassification," this paper separates physical quantities (matter, energy, signals, causal chains) from spacetime quantities (spacetime structure, expansion, connectivity, topological relations), pointing out that the definition of velocity (m/s) presupposes "matter moving through space"; when the object of discussion is spacetime itself, the concept of "velocity" no longer applies. This paper further clarifies that there is no fundamental contradiction between relativity and quantum mechanics requiring "unification"—they describe effective laws at different levels (the L4 physical level and the L1–L2 quantum level). The "superluminal paradox" that has long troubled physics is, in essence, a result of category misplacement.
This preprint clarifies a persistent category error in the interpretation of quantum mechanics and relativity by explicitly distinguishing propagation from correlation. Relativistic constraints, including the finite speed of light, apply to the transmission of energy, matter, and information through spacetime. Quantum mechanics, by contrast, permits nonlocal correlations between entangled systems that do not involve transmission, motion, or signal propagation. The apparent instantaneity of quantum effects therefore reflects the revelation of pre-existing correlation structure rather than superluminal dynamics. By maintaining this separation, the preprint shows that the finite speed of light and quantum nonlocality are not in conflict. Light is limited in speed because it propagates; quantum correlations have no speed because nothing propagates. This framing resolves common misconceptions surrounding entanglement, nonlocality, and causality without introducing hidden structures, preferred frames, or violations of relativistic invariance. The work is intended as a conceptual clarification and falsifiable interpretive framework, not a modification of quantum theory or relativity. Keywords quantum correlation nonlocality entanglement speed of light relativity causality non-signaling propagation vs correlation foundations of quantum mechanics conceptual clarification
In his seminal paper, Bell [Physics Physique Fizika 1, 195 (1964)] considers the correlations that result from space-like separated measurements on a pair of entangled particles. He uses relativity theory to motivate the Bell causal structure, then shows the existence of quantum correlations that cannot be explained classically within this causal structure. Classical explanations of such quantum correlations are possible in alternative causal structures, for instance, those that allow superluminal causal influences, but, as shown in [New Journal of Physics 17 033002 (2015)], all such alternative explanations require fine tuning (causation without correlation). Here we discuss the existence of spurious quantum correlations --- correlations that look quantum in one causal structure, but have a natural classical explanation in another. More precisely, there are causal structures that admit non-classical quantum correlations, but for which the same correlations have a classical explanation in another causal structure without fine tuning. The realisation in the other causal structure can also be achieved without breaking any natural constraints on the causal structure that follow from relativity theory. However, similarly to non-classical quantum correlations in the Bell causal structure, we find other causal structures with non-classical quantum correlations that do not have a classical causal explanation in any alternative causal structure without fine tuning.
Quantum Non-Locality and Relativity has the rare quality of being both a significant contribution to the philosophy of physics literature and a superb introduction for philosophers unacquainted with the field. Maudlin sets out to examine the implications for our understanding of the fundamental structure of space, time, and causation of what appears to be a mysterious action-at-a-distance observed in the quantum domain. Physicists and philosophers of physics have been grappling with these implications for the last half-century, and Maudlin does a remarkable job of elucidating central themes in the literature and clarifying conceptual confusions. Throughout the book, Maudlin draws out salient points from what can easily become a morass of scientific and philosophical technicalities. At the root of puzzles concerning relativity and quantum mechanics lie a few simple experimental facts. In an experimental setup in which quantum particles begin from a common source and travel in opposite directions, distant (spacelike separated) measurements of properties of the two particles are strangely correlated. These correlations have been observed, for example, in experiments which measure polarization properties of photons. A well-known theorem due to John S. (1964) expresses a constraint on the kind of correlations that measurement outcomes in this experimental setup (known as a Bell experiment) can display, in the absence of any communication between them. The surprise is that observed correlations violate Bell's theorem, meaning that the measurement events appear somehow to be influencing each other or to be otherwise connected. But there's the rub: in experiments, measurements are spacelike separated, which means they are too far apart for any force of nature travelling at or below the speed of light to traverse the distance between them in time. Faster-than-light influences seem to fly squarely (and rather quickly) in the face of everything Einstein taught us about the structure of space and time. As it is often understood, the special theory of relativity asserts that the speed of light in a vacuum is some sort of physical limit, and that matter, energy, signals, causal influence, and the like cannot travel faster than the speed of light. Do the
The origin and elaboration of our fundamental theories like quantum theory, the theory of relativity and the quantum field theories can be traced to the study of light and its properties. While developing these theories, several notions on the behaviour of light have been hypothesized as well as asserted, sometimes without any direct or compelling empirical evidence. In the context of quantum physics, there is a widespread belief that experiments on quantum correlations establish nonlocality as an essential aspect of nature. Another unshakable belief without direct empirical support is the absolute constancy of the speed of light relative to moving observers. In this paper, I argue that no experiment on quantum correlations of spatially separated photons necessitates the concept of nonlocality, and that there is no direct empirical proof of nonlocality. I also comment on the need to modify established notions on quantum light, in the context of a clear conflict between cosmology and the zero point energy of quantum electrodynamics. Then I describe the first experiments on the measurement of the true one-way speed light relative to a reference platform that is in inertial motion. The results are at variance with the belief that the speed of light is independent of the velocity of the observer.