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The size of the universe at the big bang? 
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#1
Nov2112, 05:29 PM

P: 20

So I read everywhere that everything was packed into an infinitely small space at the big bang. But then after some thousands of years the universe condensed enough to let electromagnetic waves travel through and these waves have been traveling 13.7 billion years to get here.
The problem here is of course is that electromagnetic waves travel at the speed of light, so it would seem they would have to start off 13.7 billion light years away for this to be possible. Can this be because the universe has expanded so fast that this is possible? Or is it because the universe was already infinite at the first instance after the big bang, but none the less has had everything grow further apart since then? 


#2
Nov2112, 05:48 PM

P: 166

Marcus Post #20 in the balloon sticky answers that question pretty well. Short answer: Yes, the universe was expanding faster than the speed of light at that time.



#3
Nov2112, 05:50 PM

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#4
Nov2112, 11:00 PM

P: 570

The size of the universe at the big bang?
If it is infinite in size now, then it was infinite in size then. If it is finite in size now, then it was finite in size then. How big was it in the finite case? Nobody knows. We are just guessing about that. 


#5
Nov2112, 11:52 PM

Sci Advisor
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The fact remains we do not know if the universe is finite or infinite. Both alternatives solve some problems, but, raise others.



#6
Nov2212, 02:39 AM

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#7
Nov2212, 03:26 AM

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#8
Nov2212, 03:39 AM

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#9
Nov2212, 03:50 AM

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#10
Nov2212, 04:04 AM

P: 570

Many of the early measurements of distances to heavenly bodies were off by a factor of two or more. 


#11
Nov2212, 04:21 AM

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#12
Nov2212, 04:28 AM

P: 450

http://www.astro.ucla.edu/~wright/cosmology_faq.html#RB "Since we can only look at small piece of an object that has a large radius of curvature, it looks flat. The simplest mathematical model for computing the observed properties of the Universe is then flat Euclidean space. This model is infinite, but what we know about the Universe is that it is really big. " 


#13
Nov2212, 05:22 AM

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#14
Nov2212, 10:05 AM

P: 148

(http://map.gsfc.nasa.gov/universe/uni_shape.html). How about the model of Aslanyan regarding torus model inserting both finite and infinite dimensions. Any latest finds? 


#15
Nov2212, 01:28 PM

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#16
Nov2212, 01:32 PM

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#17
Nov2212, 01:34 PM

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#18
Nov2212, 02:37 PM

P: 20

Anyway thanks for all the answers. This might be dumb but it is just a thought. If we say the universe was infinitely small at the big bang, it should never be able to grow into finite size right? Just like an infinite size should not be able to contract into a finite size? 


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