The Big Bang

I think that almost everyone heard about the big bang but i guess not everyone knows what exactly it is. Let's start off by saying that big bang is just a theory with some hard evidence but it isn't possible to make it a fact because we cannot go back in time, atleast for now. There are also many different theories about how the universe started for example Bruno Bento, a physicist who studies the nature of time at the university of Liverpool U.K., thinks that universe never had a beggining and it had always existed. But let's now focus on the big bang. We think that it happened estimatedly 13.7 billion years ago. Somewhere in the space a very hot, very dense and insanely little point appeared and started expanding. A lot of people make a mistake here, it's not an explosion as the name might suggest, it's actually an expansion. In something like a billionth of a trillionth of a trillionth of a second it underwent an insane growth spurt and had doubled in size atleast 90 times. Light chemical elements were created within the first three minutes. After about 380,000 years from the initial big bang the matter cooled enough for the photons to shine thus making the universe shine. At last roughly after 400 million years the very first stars, planets and galaxies started forming from clumps of gas. There's a lot more to talk about but these are the basics of big bang theory that everyone sould know about.

source : https://www.space.com/13320-big-bang-universe-10-steps-explainer.html