An infinitely hot & dense bit smaller than a subatomic particle that contained all of space inside that bit — smaller than an atom — and made its appearance out of nothing.
“The closer we get to the Big Bang, going backward in time, the hotter all matter must have been. At the instant of the Big Bang, the universe was infinitely hot and infinitely dense.” Henning Genz, nothingness: the science of empty space, Perseus Publishing, Cambridge, Massachusetts, 1998, page viii.
In SCIENCE – How Stuff Works What existed before the big bang?
at the end of the first paragraph on above web site – “…all the matter in the cosmos — all of space itself — existed in a form smaller than a subatomic particle.”
In UNIVERSE TODAY: What Is The Big Bang Theory? The third sentence – “At a point in time, about 13.7 billion years ago all matter was compacted into a very small ball with infinite density, and intense heat called a singularity.”
In ALL ABOUT SCIENCE: Big Bang Theory – The Premise
“Discoveries in astronomy and physics have shown beyond a reasonable doubt that our universe did in fact have a beginning. Prior to that moment there was nothing; during and after that moment there was something: our universe.”
Also see the 5th paragraph, 6th sentence:
“The singularity didn’t appear in space; rather, space began inside of the singularity. Prior to the singularity, nothing existed, not space, time, matter, or energy – nothing. So where and in what did the singularity appear if not in space? We don’t know. We don’t know where it came from, why it’s here, or even where it is. All we really know is that we are inside of it and at one time it didn’t exist and neither did we.”
BOINGBOING/Paul Davies: : What came before the big bang? “There was no such epoch as “before the big bang,” because time began with the big bang, says physicist and astrobiologist Paul Davies.” Nothing: Surprising Insights Everywhere from Zero to Oblivion, published by The Experiment] NY, March 25, 2014 Jeremy Webb (Editor)
ABOUT COM. ASTRONOMY BASICS: The Origin of the Universe: The Big Bang
The 5th paragraph:“The second part of the question, as to what existed before the Big Bang, has scientists baffled. By definition, nothing existed prior to the beginning, but that fact creates more questions than answers. For instance, if nothing existed prior to the Big Bang, what caused the singularity to be created in the first place?”
We will compare the mystery of this ‘singleton’ with the closest counterpart in the next blog – the atom.