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Thread: If galaxies are moving further away from us, aren't we the center of the Universe?

  1. #1 If galaxies are moving further away from us, aren't we the center of the Universe? 
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    I am trying to understand this expanding universe theory. What I don't understand is, if the we know that the universe is ''expanding'' due to most
    the galaxies that we observe are redshifted indicating that they are moving away from us
    , then
    that does indicate that we are the center of the universe.

    But of course, I have read and know that it is not.

    Another place I read that, all galaxies are moving away from every other galaxy. So that is why we are not at the center of the universe.

    My questions are, if that is the case, first of all, how on earth did they calculate that other galaxies are moving away from other galaxies (and us)??

    I can't visualize this scenario. I can visualize a normal explosion where everything is moving away from the center of the explosion. How can can billions of galaxies ALL move away from each other. Only way to move away from each other is to have a center and move away from it.

    Is this something like spacetime we cannot visualize??


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  3. #2  
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    Spacetime are like ballon, when we walk on the ballon there is no center. And ballon keep expanding and expanding and so we have more space to walk on the ballon!


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  4. #3  
    Universal Mind John Galt's Avatar
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    Everything is moving away from everything else. We are at the centre of the universe, but so is everything else.
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  5. #4  
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    Quote Originally Posted by John Galt View Post
    Everything is moving away from everything else. We are at the centre of the universe, but so is everything else.
    Sorry, don't get it.

    How do they calculated, figure this out??

    We can find out if other galaxies are moving away from each us, but how do we find out if other galaxies are moving away from other galaxies???
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  6. #5  
    Brassica oleracea Strange's Avatar
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    Quote Originally Posted by rohandesilva View Post
    We can find out if other galaxies are moving away from each us, but how do we find out if other galaxies are moving away from other galaxies???
    Two things. Firstly, the universe is very accurately described by General Relativity and a consequence/prediction of this is that a universe with a homogeneous distribution of mass (which is a good approximation for our universe on very large scales) must be either expanding or contracting. The red shift was seen as a confirmation of this prediction.

    Secondly, there is something call the cosmological principle: the assumption that we are not in a special place in the universe (and, conversely, the universe is similar everywhere). This is born out by observation. Based on this, we also assume we are not in the center of the universe.

    As for imagining it... can you envisage the balloon with a three-dimensional surface? No, probably not. I certainly can't; even though I have used the balloon analogy many times. I think it is more useful for showing that something can be finite (the surface area) but with no border. It can also show that the surface area can increase over time.

    "Expanding universe" is, perhaps, a poor analogy. It suggests an edge and a center. It might be better to think of it as simply the distances between things increasing (scaling) over time.
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  7. #6  
    Moderator Moderator Janus's Avatar
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    Quote Originally Posted by rohandesilva View Post

    Sorry, don't get it.

    How do they calculated, figure this out??

    We can find out if other galaxies are moving away from each us, but how do we find out if other galaxies are moving away from other galaxies???
    Consider this analogy: You are in a car. you notice that the car 100 ft in front of you is moving away at 1 mph relative to you. You also notice that the car 100 ft behind you is also moving away at 1 mph. Not only that but you notice that the cars 200 ft behind and in front of you are moving away at 2 mph. In fact, you find that any car's speed away from you is found by the simple rule of taking its distance from you, dividing by 100 and you'll get the speed in mph.

    Now if a car 100 ft away is moving away at 1 mph, and a car 200 ft away in the same direction is moving away at 2 mph, isn't the second car 100 ft away from and moving away from the first car at 1 mph? If we add a third car at 300 ft away from you isn't he 200 away and moving at 2 mph away from the second car? ( and 100 ft away and moving at 1 mph away from the second car)

    Doesn't this mean that no matter which car you choose they see the same thing, cars at multiples of 100's of ft moving away at the same multiple of mph?

    This is equivalent to what we see with galaxies; the speed they are receding at is related to the distance they are away. If you stop to work it out like we did with the cars, you find that every galaxy sees the same relationship with respect to the galaxies around it.
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  8. #7  
    Universal Mind John Galt's Avatar
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    The unaswered question is how do we measure that speed. You should google redshift. Spectra of stars, galaxies, supernovae are shifted in proportion to the speed of recession or approach.
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    Administrator KALSTER's Avatar
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    Agreed SpeedFreek. Splitting off to the Pseudo section with a Thread entitled: Ruggero Santilli.
    Disclaimer: I do not declare myself to be an expert on ANY subject. If I state something as fact that is obviously wrong, please don't hesitate to correct me. I welcome such corrections in an attempt to be as truthful and accurate as possible.

    "Gullibility kills" - Carl Sagan
    "All people know the same truth. Our lives consist of how we chose to distort it." - Harry Block
    "It is the mark of an educated mind to be able to entertain a thought without accepting it." - Aristotle
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  10. #9  
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    Then you can discuss his ideas in the thread I created here; Ruggero Santilli


    I have copied this post of yours to there as well. Please don't make any further posts on his work in the main sections, which, rightly or wrongly, is viewed as pseudoscience by the mainstream and must be discussed in the Pseudo section.

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  11. #10  
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    Imagine a rubber circle. The Milky way is just to the left of the centre, and there's thousands of other galaxies. If the rubber circle is stretched evenly in all directions, you can see all the galaxies around the milky way move around, same with the milky way.

    P.S. I'm not really into cosmology, so take this with a grain of salt.
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