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The centre of the universe

  1. May 13, 2012 #1
    I am trying to get my head around the notion that there is no centre to the universe ( should there be a subforum here for those of us who have a strong interest but a very low level of knowledge or insight?)

    Anyway ,if everywhere is effectively the centre of the universe dosn't that take us away from the idea that we are a tiny speck in a tiny unimportant and hiddden away subsection of the universe?

    I mean aren't we (also) at the centre again just like we always thought we were?
     
    Last edited: May 13, 2012
  2. jcsd
  3. May 13, 2012 #2
    It is not that hard to understand at all. Consider Earth's surface. If it was perfectly round, then there is no special point, all points are equal, and there is no centre.
     
  4. May 13, 2012 #3
    I thought I was beginning to understand:cry::rofl:
    But maybe that is what I meant .If there is no special centre then we are all the centre -as oppposed to being peripheral (which is more or less the thesis of The Hitchhiker's Guide to the Galaxy,which I guess reflects popular attitudes which I was getting at -more so than the actual physics of the thing)
     
  5. May 13, 2012 #4

    marcus

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    Geordief, you are making (what seems to me) a legitimate point that needs to be raised now and then even though it is more attitudinal or literary/philosophical than strictly objective/quantitative.
    We have feelings. How should we, based on the best up-to-date idea of the cosmos, feel about our place in it?

    First of all, in his books Douglas Adams (1952-2001) is often talking about the Galaxy rather than the whole U, and we are about 30,000 lightyears from galactic center. Our sun's place in Milky has no great distinction as far as we know. So if he gives you a feeling of being NOT at the center of things, in that context he is perfectly right.

    Second, sometimes he is talking about the entire U, but merely trying to convey an idea of its scale (not a sense of location). IMHO it is inconceivably vast. Our Galaxy is somehow comprehensible: roughly a trillion stars and 100,000 lightyear diameter. We know which direction Center is and which direction we are going in our orbit and roughly how long it will take to go all the way around. But the scale of the entire universe is, by comparison, stupendous. When he talks about that he seems to be boggled himself and to be spluttering at a loss for words---and again I think he is right.

    On the other hand Douglas Adams gets tiresome, I find, on the theme of the UNIMPORTANCE OF HUMAN HISTORY. He is so often trying to counteract the habit in every culture of mythologizing our importance in the scheme of things. The U was made for us. Our tribe, nation, species is the most significant thing about it, and so on. He harps on this theme. He employs elaborate irony to make the point. Even on Earth, he pretends, we are only the THIRD most intelligent species. It was Douglas Adams favorite joke and he found countless ways to tell it.

    Not to denigrate Adams though. He was an inspired writer who gave us unique joy and pleasure. Literary greatness comes in odd shapes and sizes. You make a valid point yourself about the DEMOCRACY OF LOCATION. In an ideal democracy the individual has the dignity of equality under law, each person's vote counts the same, and so on. In an analogous way, our model of the cosmos has no center, so all locations are equally unspecial.
    Personally i would not say "every point is center". There simply is no center AFAICS. But some people like to think of every point as just as central as every other. OK, it's just a question of the preferred choice of words.
     
    Last edited: May 13, 2012
  6. May 13, 2012 #5

    Drakkith

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    We are all at the center of our own Observable Universe at all points in time. To me this means that we all are special in the sense that each of us experiences a unique point of view that will NEVER be matched.
     
  7. May 13, 2012 #6
    the observable universe idea makes me think of a campfire. i know there is more forest out there but i cant see it. we can never prove there is more beyond though. so according to science why are we not the center of the universe?
     
  8. May 13, 2012 #7

    Drakkith

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    If you are on one side of the campfire, and I am on the other side, we will each have slightly different views of the forest, each of us will be able to see a little further in one direction. Our "visible forests" will be different. There is no reason to believe that either of us is at the "true center" of the forest. It is the same for the universe.
     
  9. May 13, 2012 #8
    thats relativity right?
    so to keep it simple each person is carrying a torch.
     
  10. May 13, 2012 #9

    Drakkith

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    That doesn't change the situation at all. Each person will see parts of the forest the other cannot.
     
  11. May 13, 2012 #10

    Chronos

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    It's a little more complicated than that. Since all other observers in the universe are 'younger' than us [relative to the age of the universe], we can make the trivial claim we see 'more' of the universe than any other observer. That universe is 13.7 billion years old. An astronomer a billion light years distant sees a universe that is 12.7 billion years old. If that same distant astronomer makes an observation NOW [in our present], that universe is 14.7 billion years old and in our future.
     
  12. May 13, 2012 #11
    It takes some time to begin to get a feel for these things that are waaaaaay beyond our everyday perceptions and experience. Things we can't often 'imagine'. For example, you know that when you see tree in the distance and it looks small, when you walk along and get close it might well be very tall. So you get a 'feel' for such perspectives; you do not find them 'surprising'. An ant would possibly be amazed because the poor ant can even see over the top of some grass.

    Is the universe infinite or is it finite and unbounded. Is there one universe or many? What do those statements even mean? They have a mathematical meaning but not ones that are easy to visualize; in fact not even meanings that every scientist agrees upon. In fact no one knows for sure.

    Chronos posts:
    and makes some observations...what do they MEAN?? Not so easy to really understand.

    Try this classic explanation about the universe; give it a read, maybe forget the diagrams and math at first...skip parts that are too complicated.....I've probably read parts of this four or five times....some of it is crazy but it is accurate.

    edit: try this simplified version first....
    http://space.mit.edu/~kcooksey/teaching/AY5/MisconceptionsabouttheBigBang_ScientificAmerican.pdf [Broken]

    more advancd:
    http://arxiv.org/PS_cache/astro-ph/pdf/0310/0310808v2.pdf

    And keep in mind different observers won't even agree on the age of the universe let alone stuff about the 'center'....

    Do you know what a mobius strip is?? Where is "the center' of that strange object? It's easy to visualize one measure of 'center' [vs width] , not so easy others [as length].

    See an illustration here: http://en.wikipedia.org/wiki/Möbius_strip

    How would two ants traveling on such a strip, two different observers, decide on a 'center' ? That's a crude analogy, like the balloon analogy of the universe, but it may give a minor insight into how not only space but spacetime is complicated.

    There is not even universal agreement on whether space is expanding or distant galaxies are 'really expanding'. Nor is there universal agreement among observers on the age of the universe. [Chronos used an agreed upon conventional measure of $13.7B years, but that is an arbitrary, but convenient, measure.]

    If you are familiar with the balloon analogy, check out this new website from one of our own people here for a discussion of what ithe baloon analogy approximates and what it doesn't:

    http://www.phinds.com/balloonanalogy/
     
    Last edited by a moderator: May 6, 2017
  13. May 20, 2012 #12
    Can you explain this part please?
     
  14. May 20, 2012 #13

    Chronos

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    Due to the finite speed of light, by the time the distant astronomer could tell us what he saw NOW, the universe would age a billion years.
     
  15. May 21, 2012 #14
    Both observers would think of themselves as the center. The center of my personal observable universe is the focal point I see the universe through, come to think of it, I do not see through one center but looking through two focal points make up my visible universe. Not to be confused with my center of mass nor the center of the earth's mass that I balance on. Centers make up everything we see as perspective and feel as real. With all the proof that there are centers everywhere I would think the universe looks more like an infinite universe where every point would be a center than a bounded universe with no center and denying that there is a center to the universe is in the model choice.
     
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