How Far Should the Principle of Relativity Go ?
The Principle of Relativity has so far been understood as the {\it covariance} of laws of Physics with respect to a general class of reference frame transformations. That relativity, however, has only been expressed with the help of {\it one single} type of mathematical entities, namely, the scalars given by the usual continuum of the field $\mathbb{R}$ of real numbers, or by the usual mathematical structures built upon $\mathbb{R}$, such as the scalars given by the complex numbers $\mathbb{C}$, or the vectors in finite dimensional Euclidean spaces $\mathbb{R}^n$, infinite dimensional Hilbert spaces, etc. This paper argues for {\it progressing deeper and wider} in furthering the Principle of Relativity, not by mere covariance with respect to reference frames, but by studying the possible covariance with respect to a {\it large variety} of algebras of scalars which extend significantly $\mathbb{R}$ or $\mathbb{C}$, variety of scalars in terms of which various theories of Physics can equally well be formulated. First directions in this regard can be found naturally in the simple Mathematics of Special Relativity, the Bell Inequalities in Quantum Mechanics, or in the considerable amount of elementary Mathematics in finite dimensional vector spaces which occurs in Quantum Computation. The large classes of algebras of scalars suggested, which contain $\mathbb{R}$ and $\mathbb{C}$ as particular cases, have the important feature of typically {\it no longer} being Archimedean, see Appendix, a feature which can prove to be valuable when dealing with the so called "infinities" in Physics. The paper has a Comment on the so called "end of time".