Photon Epoch is the 9th phase after Big Bang according to the chronology of theuniverse. It is the next step after the Nucleosynthesis Phase. It was from 20 minutes to 240000 years after the Big Bang. But, there is still an ambiguity in the time-period of this step. Some say that it started about 10 seconds after the big bang during lepton epoch and others say that it started around 20 minutes after Big Bang. We don’t know which one is true. In my opinion, it is also possible that the phase started after 10 seconds but its influence was visible after 20 minutes but, certainly, I am not sure about it!!!

If you haven’t read my article on Nucleosynthesis Phase then, I suggest you to read that first as it will help you understand this article fully…..

During this phase, the universe was filled with a hot dense plasma of nuclei, electrons, photons and neutrinos. But after 300000-370000 years, the temperature fell to the point where nuclei could combine with electron and form neutral atoms and that phase is called Recombination and Decoupling phase which is the next step.

At first, protons and neutrons were also constantly hitting each other completely in a burst of radiation and bounce off. Hydrogen is the most common element in the universe since the Nucleosynthesis phase. Till 70000 years after the big bang, the energy density of radiation is greater than the energy density of matter in the universe. This determines, how fast the universe is expanding. But after 70000 years, the universe became sufficiently large and the density of radiation dropped below the density of matter significantly.  

To know basics of the quantum world, astronomy and space exploration you can check out my book "Through the wormhole" on amazon kindle.

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                                                                      -Ratnadeep Das Choudhury
                                                      Founder and Writer of The Dynamic Frequency