“As with the expansion of the Universe, there are many misconceptions about the Big Bang. It’s time to put them right, one at a time.
Misconception 1: The Big Bang was an explosion somewhere in empty space.
In fact, in a certain sense, the Big Bang occurred everywhere in the Universe; 13.8 billion years ago, density and temperature where inconceivably high at every point in the Universe. There is therefore no “central point” from which everything originated.
Misconception 2: At the moment the big bang occurred, the whole Universe was concentrated in one point.
This is also not the case. Everything seems to suggest that the Universe extends infinitely into space, and if that is the case now, it was also the case 13.8 billion years ago. That infinite space was much more “compact” then, so the matter in the Universe had an extremely high density and temperature).
Misconception 3: The Big Bang makes the point at which time began: the moment described as t = o.
This is also incorrect. For a start, when astronomers speak of the Big Bang, they are not referring to the actual moment at which the Universe came into existence (we still know too little about that with any degree of certainty), but to the extreme circumstances in which the Universe found itself when it was a tiny fraction of a second old. More-over, it is by no means completely certain that time started with the Big Bang; other theories state that time existed before our Universe existed.” Excerpt – DeepSpace Beyond the Solar System to the Edge of the Universe and the Beginning of Time by Govert Schilling – https://www.amazon.com/Deep-Space-Beyond-Universe-Beginning/dp/1579129781