Cosmology: Part-2: The First Three Minutes:



Greetings friends!

Welcome to second part of Cosmology Series.

Please read introductory part. Link is given below.

Cosmology: Origin of our Universe:- Part-1

What happened right after “The Big Bang”?

Big Bang Timeline

Short Read; Read minutely; Enjoy:

Before proceeding further let me introduce few books which I have studied to learn Cosmology. The study of books on the Big Bang, such as “The First Three Minutes” by Steven Weinberg and “After the First Three Minutes” by T. Padmanabhan, has greatly helped me in my understanding of the origins and evolution of the universe. Name of the other books will be added on successive posts.


This book by T. Padmanabhan is an informative and engaging book that provides a comprehensive overview of the origins of the universe and the early stages of its evolution. It is suitable for both the general reader and the student of cosmology and is an excellent resource for anyone interested in the fascinating field of cosmology.

In this post, I will simply focus on some events with related pictures. Pictures will give you most of the information you need.

Here are the epochs right after the Big Bang given in sequence with time:



  1. THE BIG BANG: t =0 seconds
  2. PLANCK EPOCH- (0 to 10-43 seconds after the Big Bang)
  3. GRAND UNIFICATION EPOCH- All the fundamental forces are combined into one force because of the incredibly high temperature. t = 10-43 to 10-36
  4. INFLATIONARY EPOCH-When the Grand Unified force splits into strong and electroweak, which may have triggered a massive expansion to a size of almost 84 million light years.
  5. ELECTROWEAK EPOCH: The weak force and EM are combined. 10-36 to 10-12 seconds after the Big Bang
  6. QUARK EPOCH- The electroweak force divides into the weak nuclear force and the EM force. The Universe is a hot, dense quark gluon plasma. t = 10-12 seconds to 10-3 seconds
  7. HADRON EPOCH: – Quarks begin to join together into hydrogen nuclei. t = 1 second.

All these Epochs happened in the first second of the beginning of the Universe.

After the first second, matter and antimatter came together and annihilated each other.

First protons and anti-protons annihilated. Electrons and anti-electrons annihilated.

There was slightly more matter than anti matter (reason not known). As a result, this Universe and we exist.

Now, let us look into each epoch with a Diagram.

The Planck epoch:

The Planck Epoch.

Planck Epoch is the time from 0 to 10-43 It is known as Planck Time. At this period, the universe’s temperature was 1032 K, so high that all the four fundamental forces (gravitational force, electromagnetic force, weak force, and the strong force) of nature existed together as one super force.


During this period, the fundamental force of Gravity split apart from the other three fundamental forces, as shown in the diagram. The Electroweak force, the strong force, and the Electromagnetic force were one in Grand Unified Theory era. The temperature had fallen to 1029 K from 1032K.

The inflationary and electroweak epoch:

In this Epoch, cosmic inflation started when the universe was just 10-33 seconds. During inflation, the universe expanded exponentially and grew up from the size of a proton to a size equivalent to that of a fist. By now, the universe is 10-32 seconds old, the temperature has fallen to 100 trillion trillion (1026) K.

The quark epoch:

The electroweak epoch ended 10-12 seconds after the big bang and then began the quark epoch. Electromagnetic force and the weak force to split away from each other.  However, the temperature is still very high for the quarks to merge to form hadrons such as protons and neutrons. 

The hadron era:

Hadrons are a class of particles that are formed from two or more quarks. By this time, the temperature had fallen to an extent to allow the quarks from the previous era to combine to form hadrons. 

In the first three minutes after the Big Bang, the protons and neutrons began fusing, forming deuterium, and the deuterium atoms then joined up with each other, forming helium 4. 

The first three minutes after the big bang the most crucial minutes in the history of the evolution of our universe.

The lepton epoch:

Universe became one second old:

When the universe became one second old, its temperature became favourable enough to form another class of elementary particles, the leptons.  By this time, leptons and anti-leptons started forming, and this production continued for 10 seconds. However, the universe was still opaque as the photons could easily get scattered by these free electrons.

After 3 minutes of the big bang:

Finally, after 3 minutes of the big bang, the temperature of the universe dropped below 1 billion degrees kelvin.

At the age of 3 minutes, deuterium, protons, and neutrons combined via different possible processes to form helium nuclei.

Next Post: The beginning of nucleosynthesis: