Alan Guth’s Inflation Theory is a pioneering work. Hitherto, cosmologists had only defined what the big bang actually was without addressing the reasons for the event. Before, the inflation theory, there were several loopholes in the big bang model. In fact, some even contradicted the theory of relativity. Further the basic cosmological principles of homogeneity and isotropy also went unexplained. The Theory of Inflation solved many of these conundrums. Inflation is the phase our universe passed through immediately after the big bang. In it, it expanded rapidly leading to a flat and homogeneous universe as we know it today. The inflation phase last for a short while (10-32s) and then the universe continued to expand leisurely. By installing this phase in the main big bang theory, several problems were solved. The isotropy of the universe was a double edged sword: on one hand it strengthened the cosmological principles and the Big Bang theory, while on the other it violated the principles of relativity. This was known as the horizon problem. The conventional big bang model did not allow for such isotropy. In general physics any sort of physical interaction cannot occur faster than the speed of light. This implies that the early universe, as it was expanding, did not get time to reach an equilibrium configuration. Here an analogy can be used; heat flows from a region of high temperature to a region of low temperature, creating an equal temperature environment after some time i.e homogeneity. Similarly, the homogeneity which we see in the universe must be a result of this exchange interaction. The conventional model showed that the universe never had time to do all that, and for the homogeneity we see today, interactions musty have taken place faster than the speed of light. This paradox was solved by the rapid inflation (as suggested by Guth). According to it, before the inflation, the universe was casually connected allowing for the system to even out. After that, inflation expanded the universe while maintaining the homogeneous properties. This model is corroborated by the Cosmic Background Radiation which shows exemplary uniformity – not only it its spread all over the universe, it shows fluctuations in only 1 part per 1000! Another gaping hole in the Big Bang theory was the spatial flatness of the universe, which occurs due to the value of Ω (critical density : current density). If the value of Ω is less than one, then the universe would contract to a singularity instead of expanding (which was not happening) and if it was greater than one, then gravity would not have been able to coalesce gas to form stars and galaxies. Data from WMAP and the Sloan Digital Sky Survey show that the value of Ω is within 1% of unity. The big question that follows is why? It is very peculiar that the value is just it needs to be to avoid a gravitational collapse. This also implied that the universe must have been beyond the critical density in the past, which in turn suggested a collapse. This meant that something was constantly fine-tuning the value of Ω. Inflation offered a way out. It said that by rapidly increasing in size after the big bang, the universe was able to smoothen out the non flatness which can result in values of Ω close to 1. Aside from these two problems was the magnetic monopole problem. According to the Grand Unified Theories, magnetic monopoles should arise in very high temperatures – such as those found in the big bang and continue to exist. Detailed observations, however, failed to produced any indication that that these monopoles where present in the universe. Inflation had a solution for this too: by rapidly expanding the universe, inflation spread these monopoles so widely that no one can actually observe them. By making the universe very large, inflation infinitely diluted the concentration of the magnetic monopoles. Guth originally did not include this idea in his paper The Inflationary Universe as he thought that it was related to problems in the Grand Unified Theories themselves. This may be a small point but it needs to be highlighted as it contains the essence of scientific research that one’s conclusions should be testable, verifiable, based on solid empirical foundations. Guth had taken over some of the most baffling puzzles in one of the most fundamental problems and solved them successfully by developing his ideas from observations of a couple of years. His ideas were buttressed by gradual discoveries, Cosmic Background Radiation being one of them. The Inflation theory was generally accepted and received immense acclaim in scientific circles because of its solid foundations. Today, data from WMAP and Sloan Sky Surveys shows that the universe is not completely isotropic, but nevertheless the isotropy along with other problems have only one reliable explanation – Alan Guth’s Inflationary Universe Theory. References 1.The Inflationary Universe, Alan H. Guth, Basic Books 1997 2.The Inflationary Universe, Chapter 21: Models of the Universe, Discovering the Cosmos by R. C. Bless, pg 539-540 3.Cosmic Inflation ( 4.WAS COSMIC INFLATION THE 'BANG' OF THE BIG BANG? A. Guth (