Big-bang model, widely held theory of the evolution of the universe. Its essential feature is the emergence of the universe from a state of extremely high temperature and density —the so-called big bang that occurred 13.8 billion years ago. Although this type of universe was proposed by Russian mathematician Aleksandr Friedmann and Belgian astronomer Georges Lemaitre in the 1920s, the modern version was developed by Russian-born American physicist George Gamow and colleagues in the 1940s.

The Big bang theory itself is the outcome of thousands of brilliant minds put all together in astronomy and cosmology cautiously for exploring the origin of our universe.

Let’s move back in time. 13.82 billion years ago, what was there?

A point of singularity, extraordinary small and hot where no laws of physics were applied, the time has no existence, all four fundamental forces exist forming a unified force called super force suddenly exploded because of no reason.

”SOMETHING CAME FROM NOTHING”

In less than one second, gravity split off from the super force. Three minutes later, the temperature dropped to 10 billion degrees of Fahrenheit, an appropriate temperature for the formation of atoms to take place. Lighter element, hydrogen came into existence.

After 380,000 years, light travelled through the darkness. 4 billion years later, stars started shaping due to the presence of heavier elements such as nitrogen, oxygen, carbon etc. At the age of 13.7 billion years, the sky filled with stars and galaxies.

In 1965, Arno Penzias and Robert Wilson build a radio receiver which accidentally recorded echo or aftershock noise of big bang docking from everywhere and every corner of the universe. This was experimentally proved by NASA’S Wilkison microwave Anisotropy probe on 3 June 2001.

In February 2003, Cosmic microwave background provided a baby picture of our universe. Some of the major anomalies with the big bang theory were the unanswerable questions –

IS THERE SOMETHING OUT OF OUR UNIVERSE?

WHAT HAPPENED AT THE POINT OF SINGULARITY?

WHAT’S THE EXACT SHAPE OF OUR UNIVERSE?

HOW IS SPACE STRETCHING ITSELF FASTER THAN THE SPEED OF LIGHT?

WHAT WAS THE REASON BEHIND BIG BANG EXPLOSION?

Many alternate theories exist claming answer to these questions but none of them is experimentally verified.In 1980’s Alan Guth came up with the hypothesis of cosmic inflation i.e expanding universe which is now accepted as part of big bang theory.

Reference- https://divyanshspacetech.wordpress.com and https://www.britannica.com/science/big-bang-model