The purpose of this ‘framework model’ is primarily to generalise some of the questions that the subsequent, and more detailed, discussions of the inflationary and energy density stages of the concordance model might be expected to address. In the first section of this overall discussion of cosmology, subtitled ‘Duty of Inquiry’, a few of key ideas that are thought to underpin cosmology were outlined. In the second section subtitled ‘Weight of Authority’ we tried to build on these ideas by reviewing the concepts behind the derivation of the Friedmann equations, albeit using more classical ideas, and then proceeded to outline the evolution of the universe, which broadly aligns to the original Big Bang Model. In this final section, subtitled ‘Limits of Inference’ , we are trying to focus a little more on the issues within cosmology that may be more speculative in scope. So, it is in that context, we shall now try to remind ourselves of some questions that earlier sections have tabled:
What caused the universe to initially expand?
Why did the universe keep on expanding?
What physics describes how empty space expands?
By way of general introduction, we shall be looking at the inflation model to try to rationalise some of the physics that may explain the initial expansion back towards the concept of a singularity, where all known physics breakdown. Next, the ‘energy-density model’ will then try to rationalise why the universe, created by inflation, continued to expand based on various known and unknown energy-density components. Of course, we might pre-empt these discussions with the sort of question that most people puzzle over:
How was something created out of nothing?
While, it may be inevitable that we shall always return to questions, which exceed the current understanding of science, there is still something profoundly unsatisfying in leaving such questions just hanging there without any attempt to consider some of the wider implications. Therefore, for this reason, the discussions that follow under the heading of the framework model will also continue to engage in a degree of speculation, which it is accepted extends beyond the limits of inference and what the accepted weight of authority would probably condone, for the simple reason that our duty of inquiry is also driven by curiosity. Therefore, the framework model is simply a way of introducing some of the terminology, concepts and speculative implications of cosmology prior to discussing the main stages of the concordance model.