" The distinction between descriptive and prescriptive reference mode goes at least back to Wieringa, [2]. More detail and references regarding models and modeling can be found, e . g. , in [3]. II. The consistency of models may be conceptual or physical. In many areas of research conceptual models have become the dominating species, as conceptual models, more easily than physical ones, can be investigated by means of computing. Home Model Tour For conceptual models to be the shared property of a research community the concepts they involve must be capable of being shared. That is the case when a consensual understanding of these concepts has been achieved or can be achieved by means of definition, examples, etc. "

" The Standard Model did not accommodate massive neutrinos, because it assumed the existence of only "left-handed" neutrinos, which have spin aligned counter-clockwise to their axis of motion. If neutrinos have non-zero mass, they necessarily travel slower than the speed of light. Therefore, it would be possible to "overtake" a neutrino, choosing a reference frame in which its direction of motion is reversed without affecting its spin (making it right-handed). Since then, physicists have revised the Standard Model to allow neutrinos to have mass, which make up additional free parameters beyond the initial 19. A further extension of the Standard Model can be found in the theory of supersymmetry, which proposes a massive supersymmetric "partner" for every particle in the conventional Standard Model. Supersymmetric particles have been suggested as a candidate for explaining dark matter. Although supersymmetric particles have not been observed experimentally to date, the theory is one of the most popular avenues of research in theoretical particle physics. Home Manufactured Model References Textbooks Griffiths, David J. (1987) Introduction to Elementary Particles, Wiley, John & Sons, Inc. "