The universe we live in has a beginning, the Big Bang, no definite end since we cannot yet comprehend its whole structure, and nothing, not even time for that mater, exists outside of it. The concept of a cyclic universe has been mostly created to help physicists in their effort to understand its complexity. It is within our human nature to understand the long history of the universe, the same way as using an incomplete set of tools, not to mention creating theories that are accurate and effective. Einstein once said that the most remarcable thing about the universe is that the incomprehensible thing is that is so comprehensible.

The observations related to the measurement of the universe revealed that it was a dynamic and ever evolving place, while new discoveries in quantum physics showed how the chemical elements where being synthesized in the early stages of the universe and correlated with the Theory of Relativity, revealed its complete history. During this time however, the cosmology area of physics was mostly disregarded due to the fact that a number of observations required extremely difficult theories to explain them.

In time, even these theories came together and reunited to create a picture of the beginning of the universe, thus confirming the Big Bang model. However, there remains a big problem in the history of the universe. The universe had a clear beginning, but what was before that? Theological claims say that there was nothing before that, the universe was just created, thus the Big Bang never happened. These theories might be acceptable, but science is about what you can prove or not, it is not about what we want to be.

The Inflation theory was a result of the Big Bang theory, which, when combined with the high-energy physics and applied to the model of the early universe, reveals a wide variety of possible scenarios of the beginning of the universe, which are relatively similar, but it still does not answer the question related to whatever happened before this time.

The same problems the inflation theory what created to solve, can also reveal an alternative history of the universe through the cyclic universe theory. This states that the universe we live in is infinite in time, contracting and inflating, dying and suffering a rebirth, every few trillion years. However the theory of cyclic universe, cannot be tested, therefore is unfalsifiable, as this model predicts that the contraction of the universe into a singularity would determine space, matter, and time to fade away, thus destroying all evidence of the previous cycle.

This model is difficult to comprehend, and it might be due to the fact that our brain is wired up and trained to think in only three spacial dimensions. The star of the physics area, string theory, brings the biggest theoretical advance in cosmology, since the development of the inflation model, by better explaining the concepts of space and time. But it also poses certain paradoxes. To be in correlation with the observations in quantum physics, it predicts that we actually live in a universe that has up to 11 spacial dimensions, instead of three.

As many other theories before it, string theory didn't give much importance to the cosmology, because it was not able to predict the realistic universe we live in. However, the string theory evolved over the years through the understanding of the structure of the extra dimensions, or how to manipulate them.

One of the models using string theory to explain the whole universe suggests that the universe is only one of many included in a brane, which travel through the extra spacial dimensions, and the Big Bang was a result of the collision of two of them, which, from our point of view, would look like a singularity while in the higher dimensions it would actually be a collision.

Though string theory presents solutions to most of the quantum and cosmological effects that present paradoxes, it also remains highly controversial since it has not predicted observable events so far and cannot provide us with an experiment to test it, thus it also remains unfalsifiable.