Part 4: The Big Bang theory is the prevailing cosmological model of the birth and the expansion of the universe. However, it still is a challenge to modern cosmology to understand that very first ‘lilliputian moment’ of birth.
The chronology of the universe describes the history and the future of the universe according to Big Bang cosmology, the prevailing scientific model of how the universe developed over time from the Planck epoch. The Planck epoch is the earliest period of time in the history of the universe, from zero to approximately 10-43 (which means a 0,1 with 43 zeros instead of just 1 zero!), the smallest meaningful length of time. This is the closest that current physics can get to the absolute beginning of time, a very very short period very very little is known about.
This model of the universe’s expansion is known as the Big Bang. As of 2013 this expansion is estimated to have begun 13.8 billion years ago. The Big Bang theory is the prevailing cosmological model of the early development of the universe. The most commonly held view is that the universe was once a space-time singularity, which expanded extremely rapidly from its hot and dense state. However, while this expansion is well-modeled by the Big Bang theory, the origins of the singularity remain as one of the unsolved problems in physics.
The Big Bang is usually considered to be a theory of the birth of the universe, although technically it does not exactly describe the origin of the universe, but rather attempts to explain how the universe developed from a very tiny, dense state into what it is today. It is just a model to convey what happened, not a description of an actual explosion.
The Big Bang was neither Big – in the beginning the universe was incomparably smaller than the size of a single proton – nor a Bang: it was more of a snap or a sudden inflation. In fact, the word ‘explosion’ is really just an often-used analogy, but is slightly misleading. It conveys the image that the Big Bang was triggered in some way at some particular centre. In reality, however, the same pattern of expansion would be observed from anywhere in the universe, so there is no particular location in our present universe which could claim to be the origin. It really describes a very rapid expansion or stretching of space itself, rather than an explosion in a pre-existing space. Perhaps a better analogy, sometimes used to describe the even expansion of galaxies throughout the universe, is that of raisins baked in a cake, becoming more distant from each other as the cake rises and expands, or alternatively, that of a balloon inflating.
Thanks to Wikipedia for the Chronology of the Universe.
All articles of this series can be found here