Big Bang Theory


The big-bang theory was first propounded by Belgian astronomer-priest, Abbe Georges Lemaitre. He is also known as the father of big-bang theory. This theory is also known as the evolutionary theory. He stated that cosmic matter was in an extremely compressed state and expansion was started by the primordial explosion.

Evidence that supported the big-bang theory is as follows-

Edwin Hubble, “Stated that all the detectable galaxies are moving apart from our Milky way galaxy”

The farther galaxies are moving at a fast pace, which clearly shows that the universe is still expanding and these galaxies were close together at one time. This is also called Hubble’s law.

The following stages in big-bang theory are as follows



All the matter and energy in a universe was once a “tiny ball” singular atom with unimaginable temperate, size, and density.


The singular atom exploded destructively. Some energy is converted into the matter at the time of the explosion. It expanded within a few fractions of a second. This led to a huge expansion of the universe. As per the astronomers, it is believed that this explosion took place 13.7 billion years ago.


The period of singularity was followed by the period of very rapid expansion and cooling known as ‘Inflation’. In the third stage, the temperature dropped to 4500k (Kelvin) and gave rise to atomic matter. The universe becomes transparent. The distance between the galaxies is increasing slower than in stage two.

Alternative theory

  • Steady State Theory- It is an alternative to the big-bang theory which is propounded by Hoyle. It is considered that the universe is the same at any point in time. In other words, the steady-state universe has no beginning or ending in time.
  • Some other theories are pulsating universe theory and the anti-universe etc.