" 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. Big Model Trains References Textbooks Griffiths, David J. (1987) Introduction to Elementary Particles, Wiley, John & Sons, Inc. "

" MVC models allow the code to be more flexible later in the development process, allowing for changes that make sense at the time it makes sense to make them. Event driven In contrast, objects in object oriented programming are composed of methods and data members that attempt to model something from the domain of interest. The best models are fully encapsulated, meaning that they implement every aspect of that real world object of interest to the domain of interest, and that they don't have any extra code that doesn't model the real world. Encapsulation also means that the class is implemented in such a way that the internal representation of data is not exposed to the user of the object. The impedance mismatch between these two worlds, that of events, and that of objects, is something that's been recognized for a long time. Getting these two worlds to cooperate requires a lot of 'glue code' to make them work together. The 'model-view-controller' paradigm introduces the controller object in between the view (the GUI class) and the model (the object) to communicate between the other two objects. Model Train Magazine The actual implementation of the controller object can vary quite a bit, but the idea of an object to 'transform' events to changes in data and execution of methods is the essence of this pattern. What does "event driven" mean? Was there ever an application which did not respond to user events. "