The Big Bang theory Is an effort to explain what happened at the beginning of our universe. It describe how the universe developed from a very tiny dense state called "singularity"
This singularity have been inflated over the next 13.8 billion years
These are the steps:
A) Singularity:
This comes from observations of the cosmic microwave background, which contains the afterglow of light and radiation left over from the Big Bang.
B) The inflation:
This stage of the Big Bang was quick; Hundredth of a billionth of a trillionth of a trillionth of a second. All the energy and heat from the explosion shot out. And wherever it travelled created space
C) Primordial Soup:
This stage was when the universe began a superheated phase called primordial soup. During this time, the heat was so high neutrons, protons and electrons started to join. At the same time, there were these things called light photons that were continuously bouncing off or latching onto electrons which caused a constant glow coming from the universe.
D) Reconbination:
380,000 years after the Big Bang, matter cooled enough for charged electrons and protons first became bound to form electrically neutral hydrogen atoms and helium
The microwave background radiation hails from this moment, and thus gives us a direct picture of how matter was distributed at this early time.
In 2001, NASA launched the Wilkinson Microwave Anisotropy Probe (WMAP) mission to study the conditions as they existed in the early universe (WMAP) measured radiation from the cosmic microwave background
E) Dark ages:
During this time, clumps of gas collapsed enough to form the very first stars and galaxies. The emitted ultraviolet light from these energetic events cleared out and destroyed most of the surrounding neutral hydrogen gas.
F) Birth of Stars and Galaxies
Gravity amplifies slight irregularities in the density of the primordial gas. Even as the universe continues to expand rapidly, pockets of gas become more and more dense. Stars ignite within these pockets, and groups of stars become the earliest galaxies. This point is still perhaps 12 to 15 billion years before the present.
G)Birth of the Sun
The sun forms within a cloud of gas in a spiral arm of the Milky Way Galaxy. A vast disk of gas and debris that swirls around this new star gives birth to planets, moons, and asteroids . Earth is the third planet out.
H)Planets:
The planets in our Solar System are believed to have formed from the same spinning disc of dust that formed the Sun