" This implied the existence of non-zero neutrino masses since massless particles travel at the speed of light and so do not experience the passage of time. 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. Collectible Model Car 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. "

" While the term gained steam in the 1980s, a number of models had become famous in their own right as far back as Dorian Leigh in the late 1940s. Amongst the first models whose name and face were familiar to those outside the fashion industry include Suzy Parker, a model in the 1950s, and Cheryl Tiegs in the 1960s. Others claim that Janice Dickinson has the right to the title of first supermodel since she is credited with the creation of the term. While still others claim Lisa Fonssagrives to be the world's first supermodel and none have surpassed her over 200 covers of Vogue alone. She was in every fashion magazine during the 1930s, 1940s and 1950s from Town and Country, Life, Vogue, the original Vanity Fair to the cover of Time. The high point of the supermodel era was in the 1980s and 1990s, with some of the most famous being "The Trinity" of Linda Evangelista, Naomi Campbell, and Christy Turlington. Also in this era, models like Paulina Porizkova paved the way for an influx Eastern European models. Model Car Racing It was at this time that Cindy Crawford successfully leveraged her modelling fame into hosting her own television show, MTV's House of Style, creating and promoting many exercise video tapes, and posing in Playboy (she was the first supermodel/model to do all of these). Supermodels are, almost by definition, sex symbols. "