This is a physics forum. Physics is a scientific discipline where observations and measurements are fitted with mathematical models which describe existing data and successfully predict new values for new boundary conditions. When this happens one says that the model has been validated.

If new experiments and observations should falsify the model, one will have to reexamine the assumptions and even search for a new model.

At present the validated model we have for elementary particles is the Standard Model which uses relativistic quantum mechanics and has been tested innumerable times with laboratory and observational experiments. This mathematical model , because it incorporates special relativity, agrees with the observation that the speed of light is a constant c in vacuum. True, the value of c is serendipitous for this discussion. It is the existence of the limit that is questioned, and the only possible answer is : because the theoretical model agrees with experiment and is very predictive.

If new data falsify the standard model to the point of a new theoretical model being necessary, this new model will have to incorporate the existing structure for the cases that it has been validated, including the velocity of light limit. The standard model would become a limiting case for the new theory, for the energies and boundary conditions that were validated, in a similar way that newtonian physics emerges from special relativity at the limit of low energies.

Physics is a scientific discipline where observations and measurements are fitted with mathematical models which describe existing data and successfully predict new values for new boundary conditions. When this happens one says that the model has been validated.

If new experiments and observations should falsify the model, one will have to re-examine the assumptions and even search for a new model.

At present the validated model we have for elementary particles is the Standard Model which uses relativistic quantum mechanics and has been tested innumerable times with laboratory and observational experiments. This mathematical model , because it incorporates special relativity, agrees with the observation that the speed of light is a constant c in vacuum. True, the value of c is serendipitous for this discussion. It is the existence of the limit that is questioned, and the only possible answer is : because the theoretical model agrees with experiment and is very predictive.

If new data falsify the standard model to the point of a new theoretical model being necessary, this new model will have to incorporate the existing structure for the cases that it has been validated, including the velocity of light limit. The standard model would become a limiting case for the new theory, for the energies and boundary conditions that were validated, in a similar way that Newtonian physics emerges from special relativity at the limit of low energies.