arXiv:0811.2402 [ps, pdf, other] Title: A Realistic Cosmological Model Based on Observations and Some Theory Developed Over the Last 90 Years Authors: Geoffrey Burbidge Comments: 21 pages, conference Subjects: Astrophysics (astro-ph) This meeting is entitled "A Century of Cosmology." But most of the papers being given here are based on work done very recently and there is really no attempt being made to critically review what has taken place in the last 90 or 100 years. Instead, in general the participants accept without question that cosmology equates to "hot big bang cosmology" with all of its bells and whistles. All of the theory and the results obtained from observations are interpreted on the assumption that this extremely popular model is the correct one, and observers feel that they have to interpret its results in terms of what this theory allows. No one is attempting to seriously test the model with a view to accepting it or ruling it out. They are aware, as are the theorists, that there are enough free parameters available to fix up almost any model of the type. The current scheme given in detail for example by Spergel et al (206, 2007) demonstrates this. How we got to this stage is never discussed, and little or no attention is paid to the observations obtained since the 1960s on activity in the centers of galaxies and what they imply. We shall show that they are an integral part of a realistic cosmological model. In this paper I shall take a different approach, showing first how cosmological ideas have developed over the last 90 years and where mistakes have been made. I shall conclude with a realistic model in which all of the observational material is included, and compare it with the popular model. Not surprisingly I shall show that there remain many unsolved problems, and previously unexpected observations, most of which are ignored or neglected by current observers and theorists, who believe that the hot big bang model must be correct.