Perspective
Towards a General Theory of the Physical World Based on the Mode of Action of Its Prime Mover
1. An Approach Born of Philosophical Reflection
This approach first emerged from a philosophical reflection on motion. Several thought experiments led to the identification of a fundamental principle: every real motion implies a change of state of the physical world, within a universal present moment. Now, a change of state cannot occur without an actual cause. It is this logical necessity of an actual cause that leads to positing the existence of a prime mover of the physical world. This analysis, independent of any mathematical construction, reveals that the structure of being and that of motion cannot be understood without such a cause, acting not mechanically, but immanently and through interrelation according to the determination of the elements (indeed, from the point of view of the exercise of forces, a mechanical cause cannot be responsible for a body’s inertia).
However, this philosophical conclusion comes into radical contradiction with the theoretical framework of special relativity, which rests on the relativity of simultaneity, and thus on the denial of the existence of a universal present moment. It was in recognising this incompatibility that the Shuttle and Missile Objection was formulated. This objection shows that an inconsistency arises within relativity when one rigorously follows its own postulates applied to real bodies. Once this inconsistency is revealed, a conceptual shift becomes possible, and even necessary: to rethink the very foundations of physics.
2. The Shuttle and Missile Objection as a Gateway
The Shuttle and Missile Objection is not a peripheral critique: it is a necessary gateway to another understanding of the physical world. This thought experiment reveals that, within the framework of relativity, the assertion of relative simultaneity leads to a contradiction when applied to real bodies in interaction. By showing that this relativity of simultaneity leads to situations where an event that has occurred (such as a missile launch) becomes “not yet occurred” by a simple change of reference frame, the objection exposes a logical flaw in the system.
But this objection is also a strategic lever: it enables us to reach scientists within the very framework they regard as valid. In doing so, it paves the way for a redefinition of fundamental concepts: time, space, inertia, momentum, and mass. And this redefinition rests on another worldview, one that reintegrates actual causality and a real, immanent prime mover, distinct from quantified matter.
3. A Critique of Operationalism
This shift implies a profound critique of operationalism, which dominates scientific thought today. Operationalism grants validity to concepts only through their experimental implementation or predictive power. As a result, the foundational concepts of physics (space, time, motion) are stripped of their ontological scope and reduced to conventions of measurement or calculation.
Yet, in a realistic view of the world, a theory cannot be limited to operational abstractions. Its concepts must reflect a real structure. A worldview, if it is to serve as the foundation for a general theory of the physical world, must integrate the question of being and cause. This requires respecting the different levels of intelligibility of a physical theory.
4. Levels of Abstraction in a Physical Theory
Before defining the characteristics of such a worldview, it is worth recalling that any physical theory involves several levels of abstraction:
Worldview – often implicit, expressed in the theory’s foundational concepts.
Mathematical formulation – providing a formal framework for modelling phenomena.
Operational formulation – linking concepts to measurement procedures and experimental predictions.
A rigorous physical theory must articulate these three levels without conflating them. But in contemporary practice, the worldview tends to vanish in favour of the operational, making any reflection on ontological foundations impossible.
This is where the indispensable role of thought experiments comes in. A thought experiment tests the internal coherence of a theory by rigorously applying its postulates in extreme or paradoxical situations. This is precisely what the Shuttle and Missile Objection does: it shows that relativity, when followed through to its logical consequences, contradicts itself. The thought experiment thus becomes a bridge between philosophical analysis and scientific reconstruction.
In light of this interplay between philosophy and physics, one may propose an epistemological definition of theoretical physics:
“Theoretical physics is the pursuit of coherence in the structure and motion of the physical world, with a knowledge of quantitative proportions and according to a certain mathematical formalism, in order to model this behaviour in laws so as to predict it. The foundational concepts of a theory must express this coherence, in both the structure and motion, of the physical world.”
5. Three Points of Contact Between Philosophy and Science
From this perspective, three main modes of relationship between philosophy and science can be distinguished:
The question of the foundations of knowledge – each science, in order to produce meaning, presupposes a certain conception of reality. Understanding what each science grasps of the real requires philosophical reflection.
The critical aspect – philosophy can play a critical role by revealing internal inconsistencies or limitations of scientific theories. This is the role played here by the Shuttle and Missile Objection.
The practical encounter – when philosophy discovers principles with both ontological value and explanatory power, it can illuminate, and even guide, the formulation of the foundational concepts of science. This encounter is essential for any attempt to elaborate a general theory of the universe.
6. Towards a Relational Conception of Space‑Time
The direct consequence of this approach is the abandonment of an absolute or purely geometric space‑time, as conceived in relativity, in favour of a relational conception of space‑time. In this conception, space and time emerge from the relations between bodies. The prime mover then acts not through mechanical force, but through the immanent adjustment of relations between elements, according to a logic of interrelation.
Such a framework makes it possible to rethink mass, inertia, gravity, time, and cosmic expansion, integrating mathematical coherence, experimental scope, and genuine ontological intelligibility. It then becomes possible to envisage a general theory of the physical world founded on the prime mover, in a true articulation between physics and philosophy.
7. The Role of Thought Experiments
Thought experiments play a crucial role in this approach. They make the connection between philosophical intuition, the logical coherence of postulates, and the formal foundations of physics. It is no coincidence that the discovery of the mode of action of the prime mover arose, in this approach, from several thought experiments on motion. By analysing what any change of state – and thus any motion – presupposes, one is led to recognise the necessity of an actual cause and a universal present moment. Thought experiments are therefore not merely pedagogical or critical tools: they are at the heart of the conceptual elaboration that allows us to move beyond the operational framework of current physics, and to propose a general theory of the world grounded in ontologically rooted principles.
The Shuttle and Missile Objection: a reasoning based on several thought experiments
The Shuttle and Missile Objection can be formulated without recourse to mathematics or space‑time diagrams. It is enough to chain together three rigorous thought experiments that bring to light an internal contradiction within the framework of special relativity, when simultaneity is given a physical scope.
1. First thought experiment: simultaneity of emissions for both observers
We consider two observers: one is stationary in a train station (the station master), the other is a passenger on a moving train. Two light rays are emitted, one from the tracks at the rear of the train, the other from the tracks at the front, both towards the middle of the station.
The two observers are exactly at the same position at the moment the two light rays arrive.
This is the variant introduced, perhaps inadvertently, by Yann Le Roux. Here we assume that the two light rays were emitted simultaneously from the two ends of the station, i.e., in the platform reference frame. They then arrive simultaneously at the station master and the train passenger, since these two observers are face to face at the instant of arrival.
Yet, from the point of view of the train passenger, the distances from him to the two light sources at the moment of emission were not equal: he was moving towards one ray and away from the other. Therefore, if the speed of light is assumed to be invariant in his frame, then the two rays, having travelled different distances, should not have reached him at the same time.
→ We deduce that the speed of light cannot be invariant in at least one of the two frames, if we assume that the emissions were simultaneous for both observers. Thus, if we maintain the postulate of the invariance of the speed of light, we must accept that the simultaneity of emissions is relative: what is simultaneous in one frame (the station’s) is not in another (the train’s).
2. Second thought experiment: From relativity of simultaneity to a principle of relativity of simultaneity at the physical level
The two observers are at the same position at the moment of emission (according to the station master) of the two light rays. This is the situation classically used in Einstein’s train thought experiment. The two rays are emitted simultaneously for the station observer, at the precise moment the centre of the train passes him.
In this case too, for the train observer to maintain invariance of the speed of light, he must consider that the two emissions are not simultaneous in his frame: the front emission occurred before the meeting point, and the rear emission after. This is again a direct consequence of the relativity of simultaneity, deduced from the postulate of invariance of light speed.
At the precise moment when the two observers are at the same spatial position, a light ray (the one emitted from the rear of the train) is already considered emitted for the station observer, while it is not yet emitted for the train observer.
This means that the event “rear light emission” already exists in the station frame, but does not yet exist in the train frame, at the same place and same moment.
→ This experiment shows that the relativity of simultaneity is not limited to a difference in dating: it implies a difference in the very existence of events depending on the reference frame. Thus, implicitly, one moves to a principle of relativity of simultaneity at the physical level.
3. Third thought experiment: Logical contradiction – Shuttle and Missile Objection
Let us now take this implication to an extreme case. Suppose the station observer considers that a light ray (or, by extension, a missile) has been emitted. We are here in a space‑like interval, so he cannot actually see it, but only consider the possibility of this fact in his frame.
This observer then accelerates and adopts the reference frame of the train observer (or another moving frame).
In this new frame, due to the relativity of simultaneity, the light emission (or missile launch) has not yet taken place.
We thus have the same observer, who first considers that an event has occurred (emission), and then, after changing frame, that this event has not yet occurred (if the distance to the event and the observer’s acceleration are proportionally sufficient).
→ This leads to a logical contradiction regarding the existence of an accomplished event. If physical significance is given to planes of simultaneity, the observer must accept that a body which has existed has not yet existed, simply by changing reference frames. This reasoning, requiring no calculation, highlights a logical inconsistency in special relativity when applied to real bodies while taking simultaneity planes into account.
Conclusion
These three thought experiments suffice to establish the Shuttle and Missile Objection without any calculation:
The simultaneity of emissions for both observers is incompatible with light‑speed invariance.
The relativity of simultaneity implicitly entails a relativity of the existence of events.
A simple change of inertial frame can lead an observer to deny the existence of an event he previously considered accomplished.
This reasoning shows that the principle of relativity of simultaneity at the physical level, induced by light‑speed invariance, leads to a contradiction if taken to its logical consequences. And this is precisely what the Shuttle and Missile Objection reveals.