" Tests and predictions The Standard Model predicted the existence of W and Z bosons, the gluon, the top quark and the charm quark before these particles had been observed. Their predicted properties were experimentally confirmed with good precision . The Large Electron-Positron collider at CERN tested various predictions about the decay of Z bosons, and found them confirmed. To get an idea of the success of the Standard Model a comparison between the measured and the predicted values of some quantities are shown in the following table: Quality Measured (GeV) SM prediction (GeV) Mass of W boson 80,4120±0,0420 80,3900±0,0180 Mass of Z boson 91,1874±0,0021 91,1874±0,0021 Challenges to the Standard Model Although the Standard Model has had great success in explaining experimental results, it has never been accepted as a complete theory of fundamental physics. This is because it has two important defects: The model contains 19 free parameters, such as particle masses, which must be determined experimentally (plus another 10 for neutrino masses). These parameters cannot be independently calculated. The model does not describe the gravitational interaction. Star War Model Kit Since the completion of the Standard Model, many efforts have been made to address these problems. One attempt to address the first defect is known as grand unification. "

" For an investigator I it makes only sense to consider an entity M as a substitute of an entity O, if I can (1) establish an analogy, similarity, or similar relation between M and O that permits the substitution of O by M with respect to purpose and means, time-horizon etc. , and (2) I can actually investigate M in the required way. That implies firstly that M does not have the properties of O that prevent I from investigating O. Also other properties of O may not be properties of M. In that sense a model is more abstract than its original. Secondly, a model M will in general have properties that O does not have and that actually aid I in investigating M. What the investigator I does in modeling is formulating a problem P in terms of the original O, translate that problem into a problem P' in terms of M, obtain a solution S' of P' and translate S' into a solution candidate S of P in terms of O. Model Rocket Kit If S is actually a solution of P then the modeling process was successful and can be terminated. If, however, that is not the case then the investigator I can start over with a different problem, model, means of investigation, or relation between model and original. "