As we all know that big bang model is most accepted model for the creation of our cosmos. According to that model, it is estimated that this mega event was occurred 13.7 billion years ago. Before that it is believed that our whole universe was in the form of very very tiny ball. But after the big bang, some serious chronological events happened without which we wouldn’t see the universe as it is today.

Here, in this article, I am going to give you a very brief but informative explanations on each of the time-period after big bang to till date. In my future follow up articles, I will explain about each of these stages in detail. You will find the links for all those detailed articles in this article when all of it will be uploaded!!!

According to our current understanding, due to the extreme conditions and the violence of its very early stages, it saw much more activity and change during the first second than in all the billions of years ever since. Based on the activity and major changes in respective time-frames, astronomers divided the total timeline of universe into 15 stages with their own time-frames.

Stages of Evolution of Universe:-

We use Plank epoch to refer time from 0 to 10^-43 seconds (also known as 1 plank time) after big bang explosion. According to our current understanding, this is the closest we can get to the explosion where the current understanding of physics is applicable. Very little can be known about this period as most of the information of this period have been destroyed. All we know that the universe spanned a region of only 10^-35 (1 plank length) and all the fundamental forces of universe was either unified or had same power.

Grand Unification epoch was from 10^-43 seconds to 10^-36 seconds. It is believed that gravitational force was separated from the grand unified force while other forces remained unified and the creation of earliest elementary particles and their antiparticles started.

Inflationary Epoch was from 10^-36 seconds to 10^-32 seconds. It is believed that it was triggered by the separation of strong nuclear and in result the universe went through rapid expansion with acceleration. The elementary particles remaining from the earlier stage distributed very thinly across the universe.

Electroweak Epoch was from 10^-32 seconds to 10^-12 seconds. The extreme particle interaction during this stage created many types of particles like W and Z bosons and Higgs bosons. Due to the created of Higgs bosons, for the very first time the concept of mass was introduced in the universe as Higgs field gives the mass to respective particle.

Quark Epoch was from 10^-12 seconds to 10^-6 seconds. At this stage, universe was below 10 quadrillion degrees. Quarks and antiquarks were colliding with each other which results into annihilation. But, surprisingly a surplus of quark survived. Those surviving quarks ultimately formed the matter we know today. No one knows why only quarks survived and it’s still a big unsolved mystery in physics. Also, all the four fundamental forces finally came to their current forms.

Hadron Epoch was from 10^-6 seconds to 1 second. At this time the temperature of universe was around 3 trillion degrees. That is cool enough to form hadrons like protons and neutrons by the combinations of quarks. Production of neutrinos was also in a high rate due to the continuous collision of electrons and protons to form neutrons and in the process giving out neutrinos. The reverse was also happening. Neutrinos and neutrons were also re-combining to form proton and electron pairs.

Lepton epoch was from 1 second to 3 minutes. During this time electrons and their antiparticle positrons collided continuously and in result annihilated each other and also formed photons. Just like in Hadron epoch, photons in Lepton epoch also collided to form electron-positron pairs.

Nucleosysnthesis was from 3 minutes to 20 minutes. At this time, temperature of universe was about 1 billion degrees which was sufficient to for nuclear fusion and through this process protons and neutrons were combining to form atomic nuclei. After 20 minutes, nuclear fusion was no longer sustainable.
Photon epoch was from 20 minutes to 240000 years. This was period where the energy of universe was dominated by photons as most leptons and antileptons annihilated each other. The universe at that time was filled with plasma and opaque soup of atomic nuclei and electrons.
10) Recombination and Decoupling:-
This period was from 240000 years to 300000 years after big bang. In this stage, the electrons in universe finally bounded with nuclei to form atoms as the temperature was about 3000 degrees which is also same as surface temperature of sun. In this stage, for the very first time, universe was visible as the opaque soup of electrons and protons were cleared and photons finally free to move. This is the earliest stage of universe which we can observe. The leftover heat and photons can be observed today as Cosmic Microwave Background (CMB). To know what CMB is, you can refer to my book 'Through the Wormhole'.

Cosmic Microwave Background 
11) Dark Era:-
This period was from 300000 years to 150 million years after the big bang. During this time there were no stars to give off light. Although photons existed but the universe was truly dark. The energy level was also very low and there was minimal to no activity throughout the universe.
12) Reionization period:-
This period was from 150 million to 1 billion years. This phase was triggered by the formation of Quasars due to gravitational collapse. This phenomena ionizes the surrounding areas of universe.
13) Early Star and Galaxy Formation:-

Hubble Deep Field shows us many early stars and galaxies
This period was from 300 to 500 million years. During this period the pocket of gases become more and denser due to gravity and started to collapse under their own gravity and eventually triggered nuclear fusion creating the very first stars. Gradually, these stars formed galaxies and due to gravity, galaxies pulls themselves to form clusters and superclusters.
 14) Formation of our solar system:-
Our solar system formed between 8.5 to 9 billion years after big bang. It was formed by the left over material of earlier stars.
15) Today’s Universe:-

Today’s universe is 13.7 billion years old. Today, the same recycling of star matter continues to form new stars and thus continuing the process of universe.

As I said earlier, in my future follow up articles, I will explain about each of these stages in detail except last 6 steps as they are sufficiently explained here for a beginner. You will find the links for all those detailed articles in this article when all of it will be tune with us!!!

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                                                                    -Ratnadeep Das Choudhury
                                                      Founder and Writer of The Dynamic Frequency