The theory of the Big Bang proposes that, roughly 13.8 billion years ago, the universe originated from an incredibly hot and dense state known as a singularity. This event marked the beginning of space and time as we know it today, initiated a massive expansive process, in which the universe rapidly expanded over tiny fractions of second to create all fundamental constituents.

The question of what caused this initial singularity is still a subject of ongoing scientific inquiry, with various theories proposing different cosmological models for how such conditions could have arisen. One possible interpretation is that the singularity was caused by an extreme gravitational or quantum mechanical effect that triggered its formation.

It's vital to remember though there are still many mysteries surrounding this event just like physics' eternal unanswered questions. Nonetheless "Big Bang Theory" presents evolution/expansion stages offering substantial foundations for modern day physics while fine tuned according to incoming observations-details from astronomical measures unlike relativistically anthropic quintessence most people use up average days