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B Is the Earth the centre of the universe?

  1. Mar 8, 2016 #1
    Now before you excommunicate me, what I want to know is with all these sightings of galaxies 'within cooee' of the big bang, are they all in the same direction?

    How far can we see in the opposite direction?

    If we can see equidistant in both directions, would that not indicate that we are 'within cooee' of the centre of the universe?
     
  2. jcsd
  3. Mar 8, 2016 #2

    Chronos

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    Earth is undeniably located at the center of the observable universe - which is, of course, meaningless. The finite speed of light guarantees we can see equidistant in all directions.
     
    Last edited: Mar 8, 2016
  4. Mar 8, 2016 #3
    We dont know the geometry of the universe and there is not enough proof that there could be a cenre
     
  5. Mar 8, 2016 #4

    russ_watters

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    The evidence, or rather, the requirements of geometry to fit the evidence, make it pretty clear that there can be no center.
     
  6. Mar 10, 2016 #5
    I think this question is based on how we comprehend the geometry of the universe. If the universe is infinitely huge in 3D size (The diameter is infinite if the universe is a sphere), the earth can be regarded as the centre of the universe because any point is the centre of a infinitely big geometric structure. A common theory believes that the universe is a infinite huge body with a boundary. It seems this says is illogical because an infinity means no limit (no boundary). However, it is easy to understand. Just like the earth, we know the size of the earth (R = 6300 km around), which indicates the earth has a limited size in terms of 3D concept. But if you stand on any point on the earth walk straight you will come back to your origin, which gives you a sense that the earth is infinitely big and you can never get away from it. This infinity is constructed on 2D concept. What I mean is that the universe may be an infinity in 3D concept, but might be limited in high dimensional concepts. Perhaps the body in higher dimension has no centroid (geometrically). Therefore, based on human's view, I guess we can say the earth is the centre of the universe.
     
  7. Mar 10, 2016 #6
    Earth,or better still, you personally are by definition at the center of the observable universe,
    Higher dimensions are not observable to us if they even exist, and whatever may be beyond the limit of observation is causally disconnected with Earth.
    Which makes the question pointless, like asking in your 2D scenario where is the center of the equator.
     
  8. Mar 10, 2016 #7

    PeroK

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    If the Earth is at the centre of the universe, wouldn't the big bang have blown it up?
     
  9. Mar 10, 2016 #8
    Maybe we can proof it, indeed. But it's very probably that we'll have done a mistake, because we are seeing the universe as if we were its center... Bad sign if apparently the Earth is its center.
     
  10. Mar 10, 2016 #9

    davenn

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    you didn't quote that properly

    you are the centre of YOUR OBSERVABLE universe
    if you moved to mars or pluto or Alpha Centauri, then that spot becomes the centre of YOUR observable universe


    Dave
     
  11. Mar 10, 2016 #10

    davenn

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    again, you also misunderstand
    see my previous post
     
  12. Mar 10, 2016 #11
    I would like for the record to show that I had nothing to do with this question being asked.

    tex
     
  13. Mar 11, 2016 #12

    PeroK

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    I guess my attempt at humour was just a little too subtle for a male from Sydney!
     
  14. Mar 11, 2016 #13

    davenn

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    I saw no humour in your response... subtle, no ... non-existant, yes :rolleyes:
     
  15. Mar 11, 2016 #14

    PeroK

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    Ah well, if only we were all as clever as you!
     
  16. Mar 11, 2016 #15

    phinds

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    Hm ... now that I re-read your post and know your intent, I see the humor but I have to admit that, like Dave, when I read it the first time I pretty much missed who was posting it and took it to be a serious comment, seeing no humor at all. Guess there's just something about it taken in context that makes the humor fall flat.

    EDIT: if your snippy comment to Dave was intended as humor, I have to say that one fell flat as well.
     
    Last edited: Mar 11, 2016
  17. Mar 12, 2016 #16

    Ken G

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    There is actually an interesting issue here. Our cosmological models are going to employ the "cosmological principle" (the attribute that the universe is homogeneous and isotropic at large enough scales, so looks the same everywhere but shows change over a meaningful universal time coordinate) for as long as the evidence allows that principle to be used (which it currently does), because that is a vastly unifying and simplifying principle that makes cosmology possible. So think about that principle for a moment-- everywhere is the same, the universe looks the same from any point and from all directions, at any given age. This automatically implies that every point will seem like the center to an observer at that point.

    Thus, the real question to ask is, why does the universe obey the cosmological principle? It is a symmetry principle, so we are asking, why does the universe respect that symmetry, instead of shattering it? These are hard questions to answer, because we normally view symmetries as special and less likely. I see something unanswered behind the question "why does the Earth appear to be at the center of the universe?", but the question in no way picks the Earth out as special. Instead, it picks the universe out as special, not our place in it. We may be asking the wrong question.
     
  18. Mar 15, 2016 #17

    phinds

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  19. Mar 15, 2016 #18
    Space is expanding like the surface of a balloon being inflated. Whether you are on the Earth or another galaxy, it will appear as though everything is moving away from you. The actual space between stars and galaxies continues growing larger over time. So, everything is actually the center of space. It started as a small point and grew to the size it is now.
     
  20. Mar 15, 2016 #19

    phinds

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    Correct.
    No, it did NOT start as a small point. This is cosmology 101. It started as a hot dense plasma of unknown size, possibly infinite.
     
  21. Mar 15, 2016 #20
    Who is doing the observing? If the universe is infinite, we observe equally far in all directions from our fixed point, therefore we are at the center of our observations. But if we are at the edge of a curved space-time continuum, we may not be centered upon the universe that exists. Even an infinitely large universe may be shaped differently than we imagine it is.
    The more important question is "Why does it matter that we be the center of our universe?" Philosophers have argued that we may be a subatomic piece of the big toe of a giant and our world and solar system is akin to an atom with the moon being a revolving atomic particle such as a proton. Then our universe would include shapes and objects far more vast than we can imagine. Do we really need to be the center of all that exists to give meaning to our existence? If we accept the need to view ourselves as the most important part of our known universe, then we will be disappointed if we discover something greater than ourselves. If we accept the possibility that a greater power rules the universe, then we can take comfort in the fact that we have survived as long as we have, and chance did not create nor destroy the world.
    Another question is "When are we?" If time is an invention of our attempts to make sense of the sequence of events we experience as past, present, and future, then we may find that time is meaningless in the universe and all the events of our lives happen in an instant. "NOW" may be the beginning and end of all that happens.
    "WHY" is the question which leaves science behind and we enter the realm of the mystics and metaphysical.
     
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