Firstly, I apologise if my thinking is completely incorrect - I am by no means a physicist (yet!), I have included layman illustrations to hopefully assist in explaining my thinking.

I am imagining the big bang to be, for lack of a better word, an explosion, thus the universe to be progressively expanding:

enter image description here

Therefore, to me it seems logical to suggest that there is an edge.

If this is the case, then is it reasonable to suggest that explosion + edge = 'bright edge'? Where light projects in all directions at the edge, not just outwards into the 'nothingness'.

enter image description here

So, this brings me to my question: why, when someone looks deeply enough 'at the edge' do they see an absence of light?

Again, apologies if I'm jumping to irrational conclusions & am way off.


1 Answer 1


You are thinking that the big bang happened in a particular point in space and then expanded outwards from that point. This is not true. The big bang happened at all points in space. This is because space itself expanded in the actual bang. Therefore each point in space has its own "horizon" of 13.7 billion light years across.

This edge is due to light simply not having enough time to reach that point, therefore nothing can be observed beyond that point. It is not a literal edge.

  • $\begingroup$ Thanks for the answer mate. Im struggling to understand how the big bang happened 'at all points in space' - do you have some further reading? Many thanks :) $\endgroup$
    – HarryChil
    Mar 30, 2014 at 17:30
  • $\begingroup$ My pleasure! We're all here to ask and learn $\endgroup$
    – PhotonBoom
    Mar 30, 2014 at 17:32
  • 2
    $\begingroup$ Well stop thinking of the big bang as an explosion happening from some point. Think of it like this: If the distances between each point in space doubles, where is the centre? Everywhere and nowhere! Does this make sense? $\endgroup$
    – PhotonBoom
    Mar 30, 2014 at 17:39
  • 1
    $\begingroup$ "Wow. Yeah I get it now. Wow, thanks man." Moments and reactions like these are why people teach. =] $\endgroup$
    – ahnbizcad
    Jan 19, 2015 at 10:07

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