" 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. References Textbooks Griffiths, David J. (1987) Introduction to Elementary Particles, Wiley, John & Sons, Inc. Hobby Model Ship ISBN 0471603864 Journal Articles Y. Hayato et al. "

" Rev. Lett. 83, 1529 (1999). S. F. Novaes, Standard Model: An Introduction, hep-ph:0001283 I. Models are usually man-constituted. Model Ship Collector That justifies talking about their purpose prior to talking about their consistency. Models are used as substitutes for originals because properties of the latter are of interest and the originals are not going to be investigated themselves. "