Using Christian Doppler's Doppler Effect, Edwin Powell Hubble made an epic discovery that changed our view on the universe forever. While looking through his telescope, Edwin noticed that some stars got red-shifted over time. This must mean that these stars are moving away from us. This is the birth of the Big Bang Theory.
Firstly, let's discuss what the big bang theory is. Discovered in 1929 by Edwin Powell Hubble, the Big Bang Theory states that the universe started very hot and dense, then suddenly expanded and still is expanding to this day.
Dark Matter also plays a part in the Big Bang Theory. Dark Matter takes up 84% of the matter in our universe. In the 70s and 80s, scientists were observing the cosmos and noted that there wasn't enough visible matter in the universe to account for the apparent strength of gravitational forces between and within galaxies.This led to the belief that more than 80% of the matter in the universe is dark matter that doesn't emit light nor interact with regular matter.
That is pretty much all you need to know about the big bang for now. Theorem out!