The Inflationary Universe

The Universe, as we know today, is vast. It is not easy for us to completely map out and understand it due to its vastness. However, there is a way to understand the universe and predict its evolution over time. This can be done by understanding how the universe was created and how it has evolved since then. The creation, and evolution of our universe is now an important research topic in the field of Cosmology.

The creation of the Universe was a very highly debated topic in the scientific community. It is now believed that the universe came into existence from a singularity point, evolved, and expanded over time to transform into the universe, we know of today. This theory is known as The Big bang Theory. The problem with this theory was that it could only tell us about how the universe expanded from the highly energetic singularity. It couldn’t answer an important question of how and why there was a singularity in the first place. The answer to this question lies not in the field of Cosmology but rather was answered by Quantum mechanics. The universe was created due to a Quantum fluctuation in the vacuum. Quantum mechanics states that the vacuum in space is not completely empty but is rather a space of violent activity. Heisenberg’s uncertainty principle does not allow a complete vacuum and thus, even the emptiest places in the universe have what is known as Vacuum fluctuations. These fluctuations create a pair of particle and antiparticle violating the Conservation of Energy. Such fluctuations in the universe are then neutralized by the subsequent annihilation of these particles. The Universe was created as a result of one such fluctuation. This created the singularity which later turned out to be our universe. However, this fluctuation was not completely neutralized, like all the other fluctuations. This was a result of a very rapid expansion of the universe which is now termed as the inflation of the universe. This Inflation of the universe was a reason for the fluctuation to stay for a short time. It kept the singularity from being neutralized, just like all other fluctuations in the universe. The cause of Inflation was the Gravitational Force. The gravitational force acts attractively in most of the cases in the universe with an exception to all of these cases during the period of inflation, where the gravitational force acted on the Universe, in a repulsive way. This was caused due to the presence of high energy fields in the early universe which decayed to give this repulsive effect of gravitational force.

The inflation of the universe could explain the previously unknown results, like the uniformity of the universe and the flatness problem. The universe is uniform to high precision. This case cannot be understood for a universe that is expanding at a slow pace, similar to the present pace of the universe, as a universe expanding at this slow rate could easily become non uniform due to the effects of forces, and the second law of thermodynamics. When we add inflation to this picture, we can understand that the uniformity that exists today, was a result of the uniformity in the beginning stages of the universe. The rapid inflation of the universe could increase the size of the universe exponentially without losing its uniformity. This theory also addresses the flatness problem. The universe has an expansion rate, and gravity slows down this rate by attraction. When the Universe has a mass density more than a particular value, the expansion will eventually stop and the gravity will pull the matter back into a singularity, such a universe is called a closed universe and has the shape of the outer surface of a sphere. When the mass density is less than this particular value, we get a universe that expands forever as gravity is not powerful enough, this is called an open universe and has a shape similar to that of a horse’s saddle. If the value of mass density is equal to the value termed ‘critical mass density’ then we will have a universe that doesn’t expand or contract and is flat shaped. Our universe has a mass density very near to that of critical mass density and is thus almost flat. This is strange, as it's almost impossible for mass density to have this exact value. This can also be explained by inflation, as the rapid expansion causes the flatness of our universe. This can be imagined as a balloon that is pumped with air, the more it expands the outer surface becomes flatter. Inflation could tell us a lot about our universe but we still have a lot to learn about it to understand the final fate of our universe. Will it be closed, open, or just flat?