Final answer:
The inflationary model proposes that the universe underwent rapid expansion, known as inflation, shortly after the Big Bang, explaining its flatness and uniformity. The model accounts for the uniform CMB temperature and expounds on the formation of structures within the early universe, including galaxies from concentrated regions of matter.
Step-by-step explanation:
The Inflationary Hypothesis
Physicists have developed a theory known as the inflationary model to explain certain characteristics of the universe, such as its flatness and uniformity. This hypothesis suggests that shortly after the Big Bang, before the emission of the Cosmic Microwave Background (CMB), the universe underwent a period of incredibly rapid expansion. This period, known as inflation, lasted between about 10-35 and 10-33 seconds after the Big Bang, during which the scale of the universe increased exponentially by a factor of about 1050. These inflationary models adjust for the uniform temperature observed across the CMB and the density of the universe being so close to the critical density. They also help explain how the early hot, dense state of the universe resulted in the large-scale structures we see today, where the concentrated matter eventually formed galaxies.
Formation of Structure in the Early Universe
Theorists suggest that in the early universe, a uniform hot 'soup' of particles vibrated, much like sound waves. These vibrations could have created regions of higher density, which, upon cooling, resulted in the 'frozen in' concentrations of matter from which galaxies eventually formed. The Big Bang model is supported by the isotropic nature and the expansion of the universe, along with CMB evidence. Overall, the model of an inflationary universe fills in the gaps left by the traditional Big Bang model and provides a unified picture of how the early universe evolved, guided by the principles of grand unified theories (GUTs).