" What has been presented here so far essentially is due to Stachowiak, [1]. To understand how then models are used in more detail one needs to distinguish from each other the various reference modes in which the investigator puts the model with respect to the original . The reference modes that perhaps are most important in computing are: (1) descriptive, i. e. , the model describes the original. If the deviation from model to original cannot be tolerated then the model has to be changed. Analysis models are in a descriptive reference mode to their originals. Model Train (2) prescriptive, i. e. "

" 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. 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. In 1999, the Super-Kamiokande neutrino observatory reported that it had not detected proton decay, establishing a lower limit on the proton half-life of 6. 7× 1032 years. This and other experiments have falsified numerous GUTs, including SU(5). Another effort to address the first defect has been to develop Preon models which attempt to set forth a substructure of more fundamental particles than those set forth in the Standard Model. Model Oz In addition, there are cosmological reasons why the standard model is believed to be incomplete. Within it, matter and antimatter are symmetric. "