Chronology of the Universe
This article explains about the Big Bang & the main stages of our Universe involved with it.
Today almost majority of the people in the world support the fact that the Universe originated from a singularity and is still expanding.This theory is called the Big Bang. That Singularity had high amount of energy & density . Nobody knows or can’t even predict what happened even before the Bigbang. But the stages after the Big Bang, have been approximately deduced by many of the scientists in the world. It consists of 5 stages mainly. Let’s deep dive into it.
Very Early Universe
The universe at the time of first pico-second(10 to the power of -12) right after the Big Bang is said to be in this stage. It includes a plank epoch, during which currently understood laws of physics may not apply. In fact there were no fundamental forces as such like Gravitational, Electromagnetic, Strong & Weak Nuclear forces. They were in the emergence stage and the Universe was very hot. The expansion is totally controlled by the radiation of the Universe at that time and no other forces. As the universe expands little by little , the cooling process of the Universe began.
Tiny Ripples were present in the universe during this stage and they are considered to be the foundation of the generation of large scale structures which we see right now.
The Early Universe
This stage lasted around 3,70,000 years initially. Almost all the subatomic particles are formed in this stage which is the main component of everything we see right now in front of us. That is why we are made of star dust.
In the initial stages at about 1 second, Neutrinos were decoupled, primordial black holes were formed(since the density of the matter was very high in the early stages of the universe). And from about 2 minutes, composite subatomic particles like protons, neutrons were formed which are fused to form elements like deuterium which in turn formed Helium — 4 one of the main constituents of the stars.
At about 20 mins, the universe became cold enough to stop nuclear fusion but still it was hot enough for neutral atoms to exist. At around 47000 years, as the universe cools, its behaviour is dominated by the matter rather than the radiation. At around 100000 years, the first molecule helium hydride was formed and later at around 3,70000 years , Universe was cool enough for the neutral atoms to exist.(namely hydrogen, helium & lithium in traces & they went to their neutral state very quickly by releasing photons-light)
The Dark Ages & Large Scale Structure Emergence
From 3,70,000 years to 1 billion years, the Universe is said to be in this stage.
During this stage, the only sources of light, the hydrogen clouds , were collapsed slowly to form stars & galaxies. So, there were no new sources of light, which in turn decreased the amount of photons emitted by these neutral atoms like hydrogen. As time flies, these decoupled photons were gradually red shifted and later shifted to non — visible wavelength for about 3 million years leaving no visible light.So, this is called Dark Age.
Around 10–17 million years, the temperature of the universe is such that there were chances for existence of water in liquid state in some parts of the Universe. There has also been speculations that life could have arisen somewhere at this point of time.
Slowly stars & galaxies were started forming in the later stages. They explode after some 300–500 million years which in turn release supernovae . This again leads to the formation of new stars . As time flies, large clusters of galaxies were formed which we see right now.
The Universe gradually transitioned into the one which we see right now.
The Universe as it appears today
From 1 billion years to 12.8 billion years, the universe looked almost similar as it appears today. It will infact look the same for about some billion years in the future.
The thin disc of our galaxy formed at about 5 billion years, the solar system originated at around 9.2 billion years and the early traces of life on earth emerged about 10.3 billion years from the big bang
From about 9.8 billion years of cosmic time, the universe started accelerating in the expansion process which in turn indicates that we are still in the early stages of the big bang expansion.This will continue for some more billion years but as humans we are not quite sure which path our universe will take in future.
The far future & the ultimate fate
Many Scientist proposed that at some point of time in future, the Universe stops expanding itself and no new stars will be born . There are some 3–4 theories which talks about this.
Heat Death
As the universe expands & expands, as a result it becomes very cold & dilute. The density of the universe will decrease eventually which in turn leads to thermodynamic equilibrium. In time all the structures will decompose to subatomic particles and the universe which we see will no longer exists.
Big Rip
In this case, as the universe expands , at some point in time, the accelaration or force will be such that even all the structures including me & you(if only we are alive😉) will be pulled apart and no matter exist.Even subatomic particles.
Big Crunch
In this case, when the Universe reaches its final stage of expansion, the expansion will be stopped and the gravitational forces between the particles will influence the Universe now. Therefore the Universe will start to contract making the entire process reversible and as a result a singularity will be created .
There are a few more theories which depict about the fate of the Universe which you can browse yourself if you are interested in reading it.
So that’s it, right now we are wandering in a large ocean of Star Dust and we don’t know where this will lead to finally 😉.
