The document: DOI: 10.13140/RG.2.1.4285.9289

Mathematically the question is to determine all the transformations realized between some coordinate systems which have a physical reality for the experimenters: each of these four-dimensional coordinate systems is formed by a cartesian and rectangular coordinate system of a three-dimensional Euclidean physical space, and by a particular temporal parameter which is qualified as cartesian and whose construction is specified. We obtain then a group of nonlinear transformations that contains the Poincaré group and is described by about fifteen real numbers.

Interpretation:

1 / The paradox of Ehrenfest:

If the elements of a family of observers are not motionless the ones with recpect to the others, in other words if their world lines are not elements of a unique physical space, then even in the context of classical kinematics, how they can manage to put end to end their infinitesimal rules to determine the length of a segment of curve of their reference frame (each will naturally ask his neighbor not to move until measurement is ended) ? this is the basis for the proposed solution to Ehrenfest paradox. Inspired by the expression of the law of Hubble, every theory must provide explicit or implicit assumptions to compare "the proper distance" D (which can vary over time) which separates an arbitrarily chosen experimenter P from a certain object, and "the proper distance" D' which separates another arbitrarily selected experimenter P' from the same object and this because it is admitted that this concept of proper distance has a physical meaning even in a non-comoving reference frame.

2 / The authorized relative motions are quantified:

I establish an Eulerian description of the construction of all the physical spaces of the "classical kinematics" and an Eulerian description of the construction of all the physical spaces of nature in the context of the new theory. In classical kinematics all the authorized relative motions between observers can be described by two arbitrary functions of the universal temporal parameter (one of the rotation and one of the translation) and in the context of the new theory, all the authorized relative motions between observers are described by at most 15 real numbers. A notion of expansion of the universe is established as being a structural reality and a rigorous formulation of the experimental law of Hubble is proposed.

Thank you.

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