Answer : The chronological order events related to the formation of the universe with the stages in which they occurred are given below;
- Expansion from an infinitely hot point - Which is also called as the Planck era from which the big bang theory arrived. It is assumed that from the moment of initial expansion to
seconds afterwards, and many also refer that it was from an infinitely hot point.
- Hydrogen fuses into helium - This was called as the era of Nucleosynthesis which resulted from the Fusion and it continued in the Era of Nucleosynthesis ( which is 0.001 seconds – 3 minutes)
- The first neutral atom begins to form - Era of atoms, it began in around 380,000 years – 1 billion years or so.
For better understanding please refer the attachment.
