Speed of light

Is there some inaccurate reasoning at the root of special relativity?

" It was once assumed that the speed of light was invariant with respect to the aether, and that it could therefore not be invariant with respect to the Earth. Although the aim of the Michelson-Morley experiment was to confirm this assumption, the results obtained in the latter experiment seem to show on the contrary that the speed of light is invariant with respect to the Earth. It was this finding that probably led Albert Einstein to adopt the following reasoning: if the speed of light is invariant with respect to the Earth, then since the Earth is a moving body, the speed of light must be invariant with respect to any body in a state of inertia. If we apply this reasoning to Einstein’s train thought experiment, this means that if the speed of light is invariant with respect to the station, then it must also be invariant with respect to the train, which is in constant motion with respect to the station. However, as I propose to establish here, this reasoning is not entirely accurate. As we will see, it is probably far more reasonable to expect the speed of light to constantly adapt to the current spatial configuration, although no proof of this hypothesis has been definitely established so far " — Extract from the book "Paradox of the invariance of the speed of light".

There are not necessarily only two possible solutions regarding the speed of light:

Einstein’s solution (invariance of the speed of light with respect to different inertial frames of reference);

Lorentz’s solution involving a privileged frame of reference.

On this subject, if you search for "Lorentz ether theory" on Google, you will find:

"In Lorentz's Ether theory, the speed of light is isotropic only in the Ether frame and anisotropic otherwise; inertial frames are not physically equivalent."

There is at least a third possibility

The possibility of locally privileged frames of reference.

This point of view has not been considered by physics since the birth of special relativity. It leads to a new vision of space-time, a new conceptual framework for physics.

"I am merely seeking to show that, from a theoretical standpoint, physical invariance of the speed of light implies relativity of simultaneity at the physical level. However, since the latter leads to contradictions, this allows us to definitively eliminate the first possibility. And since Lorentz’s interpretation can likely also be ruled out, the only remaining interpretation is the one I propose: a speed of light that is locally invariant with respect to certain inertial observers, due to a constant adaptation of the speed of light to the spatial configuration (*). Moreover, this aspect could probably be measured..."
— Extract from the book "And He Was Hovering Over the Waters: Towards a New Vision of the Physical World ?"

(*) I might perhaps have written: "due to its dependence on the spatial configuration." One must, for example, take into account the Shapiro effect.

Video Resource:

Is there really a limit to speeds? — Marc Lachièze-Rey (Fr)

I posted these messages under the video :

April 28, 2028: Thank you for the explanations on velocity; however, a few remarks on related topics. The fact that clocks do not tick at the same rate depending on their position in space or their motion in no way implies that time does not exist. It simply means that the rate of physical processes depends on spatial conditions, which is very different from a denial of time itself. One cannot arbitrarily rule out the possibility that two ‘identical’ clocks, placed in different spatial conditions — for example on two different floors of the same building — may run simultaneously at different rates. Likewise, the fact that one cannot determine the simultaneity of two distant events independently of any measurement convention does not in any way imply that simultaneity does not exist. This is a limitation of our measurement procedures, not an ontological property. Furthermore, the fact that we only measure proper durations — that is, local times associated with particular physical processes — does not imply that time as such does not exist. Here again, one confuses an operational constraint with a conclusion about the nature of reality. Marc Lachièze-Rey overlooks these distinctions, moving from a statement about experimental limitations to a much stronger ontological interpretation, which nevertheless remains open to debate.

April 29, 2028: That being said, I find Marc Lachièze-Rey’s explanations of velocity very interesting. Replacing the notion of speed with that of velocity seems to open up an interesting line of thought. One might see in this a way to more finely relate the propagation of light to the structure of space.

April 30, 2028: Speed measures only how fast motion occurs, whereas velocity also specifies its direction. However, this direction is generally defined within an abstract space. One can go further by considering that velocity expresses an orientation within the real spatial structure, that is, within the set of relations that constitute physical space.

The energy–momentum four-vector unifies energy and motion within a geometric framework. A possible extension would be to define them as depending on the relational configuration, both local and global, which would amount to replacing a purely geometric description of motion with a relational one.

This is a line of reflection; I do not yet master its technical aspects, but it seems to me worth exploring.

May 4, 2028:  Carlo Rovelli has made it possible for Aristotle’s definition of time to become non-circular, although this was probably not his primary intention. For Aristotle, time is the number of motion with respect to before and after, where ‘number’ is understood as that which allows counting. Now, Carlo Rovelli points out, from within Aristotle’s perspective, that one can count a motion by using another motion. From this point on, it becomes sufficient to replace “before and after,” which are temporal notions, with the idea of going from one point to another for a given moving body. Indeed, if an obstacle is placed, one can clearly see in which direction the motion proceeds, without needing to rely on these temporal notions. This means that Aristotle’s definition of time, clarified by the precision brought by Carlo Rovelli, can very well still be considered valid.

From there, instead of speaking of four dimensions—three of space and one of time—one can envisage a description based solely on spatial dimensions, by integrating temporal variations into the very structure of the relations between bodies. Such a perspective becomes possible within a fully relational approach to space and motion.

Philippe de Bellescize