Please forgive my ignorance. I dare say that these questions arise from me trying to understand the nature of the Universe using Newtonian physics. There are a few things that really bother me when topics such as red shift and expansion are discussed.

1) We can view a Galaxy that is 30bn light years away because the light we are seeing it as it was 13bn years ago, and at that time it was only 13bn light years away. So, it has travelled 17bn years further in the last 13bn years? Faster than the speed of light?

2) 13bn years ago, it was 13bn light years away. That is around the time of the big bang. How did it manage to get that far away so soon after the Universe began.

3) How is the known Universe even as big as 40bn light years, after only 13bn years in existence.

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    $\begingroup$ 13 billion years ago, the object was not 13 billion light-years away. $\endgroup$ – HDE 226868 Sep 16 '14 at 23:26
  • $\begingroup$ Also, a word of advice: Don't use Newtonian physics when trying to understand the large-scale of the universe. $\endgroup$ – HDE 226868 Sep 17 '14 at 1:19

The current explanation is that "space" is continuously created in the intergalactic void, "pushing" the galaxies apart. From what i understood ( i am also ignorant ), the current rate at which "space" is created is expressed by the Hubble's constant 67.15 ± 1.2 km/s/Mpc ): for every million parsecs of distance from the observer, the rate of expansion increases by about 67 kilometers per second, which means that the distance between 2 points that are 1 megaparsec apart grows with 67km every second; between 2 points that are 2 megaparsecs apart with 134km/s, and so on so the relative speed between 2 points that are 5000 Mpc apart would be 335000 km/s which is more than the speed of light. In fact, two objects at this distance would not move, but 335000km worth of "extra space" would be "created" between them every second.

However in the last week there was an article depicting the shape of the universe, and it is hard for me to understand how it got to look like this : http://ifreepress.com/wp-content/uploads/2014/09/laniakea.png


  • $\begingroup$ The picture isn't of the shape of the universe; it's supposed to depict the Laniakea supercluster, which is certainly not the size of the universe. I'm not sure how realistic it is, though. I would imagine not very. $\endgroup$ – HDE 226868 Sep 18 '14 at 22:26

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