Space after the big bang occurred have expanded dramatically. However at the same time the big bang happened it started to expand from that moment so what can we find before that point. For example, if we went back to the point where big bang happened what can we see? what is the point before it? is it nothingness?
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1$\begingroup$ Possible duplicates: physics.stackexchange.com/q/136860/2451 and links therein. $\endgroup$– Qmechanic ♦Commented May 13, 2020 at 5:05
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2 Answers
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The big bang happened everywhere, so the question "what can we find if we went back to where the big bang happened" doesn't make sense. You (and everything else in the observable universe) is where the big bang happened. What you see is what you find if you "went back to where the big bang happened".
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As Allure says , in the first Big Bang model where everything is at a point at time zero, all space points in the present universe would come from that original "bang" point, and there is no "before" that model. It is a classical mechanics and General Relativity model.
In the present day the Big Bang model no longer starts from a point, but from a fuzzy region at the beginning of time controlled by effective quantum dynamical equations.
This was necessary in order to explain observations.
The image illustrates this, and again, in the BB model there is nothing before the first quantum mechanically fuzzy region on the left. The mainstream answer again is that there is nothingness before that fuzzy region.
There exists proposals for different cosmological models and a new question should be reformulated for a particular one, (although the Big Bang is the mainstream one) .
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$\begingroup$ Allure is not saying that the Big Bang happened at a single point, but that it happened at all points. The Big Bang could have happened everywhere in an already spatially infinite manifold. But even so we have no idea what happened at $t=0$, saying the region was fuzzy or that it is governed by “effective quantum” equations is speculation. $\endgroup$– bapowellCommented May 14, 2020 at 11:55
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$\begingroup$ @bapowell I am stating the speculation in the present Big Bang cosmological model, if you look at the links, it is there as standard. $\endgroup$– anna vCommented May 14, 2020 at 12:48
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$\begingroup$ That the big bang happened everywhere at once is not speculation--it is borne out in our observations of a homogeneous and isotropic universe. The current Big Bang model makes no assertions about the nature of the big bang itself, so it is unhelpful to talk about "fuzzy regions" or "effective quantum dynamics", which are not accepted concepts in the field. $\endgroup$– bapowellCommented May 14, 2020 at 16:33