<p>An explosion is an expansive movement <em>in space</em>.</p>
<p>The Big Bang is the creation and expansion of space itself. It expands at the same rate at every place in every direction (though the rate of expansion is changing with time).</p>
<p>When we speak of the shape of the universe (either flat, or positively or negatively curved) we mean curvature of this space itself to be such that the matter in the universe is just dense enough thus there is exactly enough matter so that expansion will stop expanding eventually at infinite time (flat spacetime), will expand forever (negatively curved spacetime) or collaps back to a singularity in a finite time (positively curved spacetime). Thus 'flat' or 'curved' does not mean that one of the spatial dimensions you (and we all) look at with our eyes is bent or not bent - it's rather bent or not bent in time.</p>

CC BY-SA 4.0
2022-11-30T21:46:20.583Z
2022-11-30T21:46:20.583Z
planetmaker
<p>When an explosion takes place, the contents get scattered in every direction. So how is it, that after the &quot;Big Bang&quot;, everything only went in one direction, to form a flat Universe?</p>

CC BY-SA 4.0
2022-11-30T21:34:34.390Z
Big bang isn't an explosion.  Its not even "like" an explosion. The question contains a non-sequitor. In the big bang the early universe was hot, dense and expanding.  Nothing was going anywhere. So "everything went in one direction" is also wrong.  That doesn't really leave much left of the question.  (and the answer to the fragment that remains is "probably inflation")
James K
CC BY-SA 4.0
2022-11-30T22:14:28.907Z
This is what I still find very confusing because some people describe the "Big Bang", as something that was the size of an atom, that contained all the matter that is in the Universe today, when it exploded. How could so much have been contained in something so small , it doesn't make sense.
Peter U
CC BY-SA 4.0
2022-11-30T22:18:49.270Z
Who says that? They are wrong
James K
CC BY-SA 4.0
2022-11-30T23:47:42.057Z
Can you provide a source that claims everything only went in one direction?
Greg Miller
<universe>
Shape of the Universe
Peter U
# Shape of the Universe

(Asked by: username_0 on 2022-11-30)

When an explosion takes place, the contents get scattered in every direction. So how is it, that after the "Big Bang", everything only went in one direction, to form a flat Universe?

**Tags:** universe
> **Comments:**
> **username_1**: Big bang isn't an explosion.  Its not even "like" an explosion. The question contains a non-sequitor. In the big bang the early universe was hot, dense and expanding.  Nothing was going anywhere. So "everything went in one direction" is also wrong.  That doesn't really leave much left of the question.  (and the answer to the fragment that remains is "probably inflation")  
> **username_0**: This is what I still find very confusing because some people describe the "Big Bang", as something that was the size of an atom, that contained all the matter that is in the Universe today, when it exploded. How could so much have been contained in something so small , it doesn't make sense.  
> **username_1**: Who says that? They are wrong  
> **username_2**: Can you provide a source that claims everything only went in one direction?  

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## 1 answers

### Answer by username_3 on 2022-11-30. Score: 2

An explosion is an expansive movement *in space*.

The Big Bang is the creation and expansion of space itself. It expands at the same rate at every place in every direction (though the rate of expansion is changing with time).

When we speak of the shape of the universe (either flat, or positively or negatively curved) we mean curvature of this space itself to be such that the matter in the universe is just dense enough thus there is exactly enough matter so that expansion will stop expanding eventually at infinite time (flat spacetime), will expand forever (negatively curved spacetime) or collaps back to a singularity in a finite time (positively curved spacetime). Thus 'flat' or 'curved' does not mean that one of the spatial dimensions you (and we all) look at with our eyes is bent or not bent - it's rather bent or not bent in time.


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