How come a tiny atom developed into an almost infinite universe

Question

and if it is true why ar there not more "big bangs" going on around the outside and how do we know that this happened

Answer 1

It wasn't an atom, it was (probably) a singularity.  This is not part of the big bang theory, which is why I say probably.

It was a singularity the size of an atom, but with the mass/energy of the universe.

And maybe there are more big bangs going on, but how would we know if they were outside of our universe?  For that matter, is 'outside our universe' even a sensible concept?

We know that we are expanding from what was once a very small size because of measured expansion of the universe and cosmic microwave background radiation.

Answer 2

static electricity.

our Universe is nothing special, just one of many Universes all laying side-by-side separated only by quantum reality.

if these Universes aren't completely at rest with each other (no reason to assume they are) then you get the old glass rod and silk static spark.  BANG.

Answer 3

It was most likely no single atom, as matter, as you know it, was not existing around the big bang. No other big bang is going on, because we don't experience similar energy densities in the universe to create similar conditions as around the Big Bang.

Answer 4

Some of the better ideas do not have an "all at once" or singularity feature. For example, a little matter formed from the quantum vacuum.  It warped the surrounding space, creating more space.  This new space then creates more matter and energy.

But the Big Bang does not currently have an answer to how it got started.  It's much better at what happened once it got started.

There very well could be more big bangs.  But they're not part of our Universe, so we won't know for sure.