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How does inflation fit into the position of the Earth?

  1. Sep 22, 2009 #1
    You can get a calculator and start counting the errors and false assumptions contained below if you want.. but I gotta ask..

    If the furthest we can see is 14 billion light-years away (because it's been 14 billion years since the big bang and that's all the time light has had to travel such a distance), then the objects we see at the edge of our observable universe were from shortly after the big bang.

    Question 1: If Earth were at the center of the universe, then we should be able to observe objects at 14 billion light-years in all directions. If Earth wasn't in the center, shouldn't we see objects 14 billion light-years in the direction of the center, while only seeing a smaller amount of objects in the opposite direction? Would that allow us to calculate our position relative to the big bang?

    Question 2: When considering an object 14 billion light-years away in some direction, and an object 14 billion light-years away in the opposite direction... shouldn't both objects have been in the nearly the same position 14 billion years ago, near the time of the big bang? How is it we can look at two objects when they were starting to diverge from one another from 2 different perspectives at the same time?
  2. jcsd
  3. Sep 22, 2009 #2


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    We can actually see further than 14 billion light-years, as a result of the universe's expansion since the big bang. The so-called particle horizon, the edge of the observable universe, is about 46 billion light-years away.

    1: We have taken counts of galaxies all over the sky, and the density is roughly the same in all directions. Our observable universe appears essentially isotropic in its large-scale distribution of matter. We cannot say what is outside our observable universe, but it may or may not be isotropic. There is no "center" of the big bang. The big bang happened "everywhere" at once. The best analogy is raisin bread rising in the oven -- every raisin moves away from every other raisin, and every raisin sees the same view.

    2: All distant galaxies are moving away from us, and the more distant galaxies are moving faster. This is called the Hubble flow, and it is what led to the formulation of the big bang theory. The galaxies were not formed immediately after the big bang -- the formation took quite a long time, at least half a billion years. By the time they formed, they were far enough away from our own galaxy to been as independent, compact objects.

    - Warren
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