According to the big bang theory, how long ago did the universe begin?

Our whole universe was in a hot, dense state

Then nearly fourteen billion years ago expansion started, wait

The earth began to cool, the autotrophs began to drool

Neanderthals developed tools

We built a wall (we built the pyramids)

Math, science, history, unraveling the mysteries

That all started with the big bang! Hey! Since the dawn of man is really not that long

As every galaxy was formed in less time than it takes to sing this song

A fraction of a second and the elements were made

The bipeds stood up straight, the dinosaurs all met their fate

They tried to leap but they were late

And they all died (they froze their asses off)

The oceans and Pangea, see ya wouldn't wanna be ya

Set in motion by the same big bang!

It all started with the big bang!

Big Bang theory says that our universe began 13.7 billion years ago