" References [1] Stachowiak, H. ; "Modell" (In German); In: Seiffert, H . Handlexikon zur Wissenschaftstheorie; Deutscher Taschenbuch Verlag; 1989; pp. 219 - 222. [2] Wieringa, R. J. ; "Algebraic foundations for dynamic conceptual models"; PhD dissertation Free University of Amsterdam; 17 May 1990. Radio Controlled Model Ship [3] Kaschek, R. ; "Modeling ontology use for information systems"; In: Althoff, K. "

" 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. 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. The so-called grand unified theories (GUTs) hypothesized that the SU(3), SU(2), and U(1) groups are actually subgroups of a single large symmetry group. At high energies (far beyond the reach of current experiments), the symmetry of the unifying group is preserved; at low energies, it reduces to SU(3)×SU(2)×U(1) by a process known as spontaneous symmetry breaking. Building Wooden Model Ship The first theory of this kind was proposed in 1974 by Georgi and Glashow, using SU(5) as the unifying group. A distinguishing characteristic of these GUTs is that, unlike the Standard model, they predict the existence of proton decay. "