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Thread: Question: Space expansion and observing distant objects from Earth

  1. #1 Question: Space expansion and observing distant objects from Earth 
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    Hello everyone,

    I am absolutely new to this forum and find it absolutely spectacular. I am in a process of "eating" resources from the sticky post (which is brilliant btw), but there is one particular thing that eats me, so I figured I will try to ask straight away (hope that is ok with you).

    Scenario:
    1.) We observe distant objects through light that traveled to us.
    2.) Principle of space extension (couldnt think of a better word) basically means distance between two objects can increase at greater pace than is a speed of light (is this correct?)

    Question:

    Is it possible that we do not see large part of the universe, because the distance between these objects and us is increasing at a greater pace than is a speed of light (and hence light from these objects will never reach us, if the pace doesnt decrease for long enough period of time).

    Sorry if this question has been here allready and please dont hesitate to link me some resources on this matter if you happen to have some.

    Cheers


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  3. #2  
    Brassica oleracea Strange's Avatar
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    Quote Originally Posted by tehpanta View Post
    Is it possible that we do not see large part of the universe, because the distance between these objects and us is increasing at a greater pace than is a speed of light (and hence light from these objects will never reach us, if the pace doesnt decrease for long enough period of time).
    Absolutely, yes. The part of the universe we can see is called the Observable Universe; it is assumed that the universe carries on, largely unchanged, beyond that. We don't know how large the whole universe is, but measurements suggest it is very large if not infinite.

    Good overviews here:
    Observable universe - Wikipedia, the free encyclopedia
    Frequently Asked Questions in Cosmology

    Note that it is slightly subtler than just "we can't see them because they are receding faster than light". Apparently it is (in principle) possible to see things which are receding faster than light - but I haven't got my head round this so I won't say any more in case I get it wrong.


    Without wishing to overstate my case, everything in the observable universe definitely has its origins in Northamptonshire -- Alan Moore
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    Brassica oleracea Strange's Avatar
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    And on measurements of the size:
    In short, the universe appears to be quite "flat," meaning that its shape can be described well by Euclidean geometry, in which straight lines are parallel and the angles in a triangle add up to 180 degrees.

    "One of the reasons we care is that a flat universe has implications for whether the universe is infinite," Schlegel said. "That means — while we can't say with certainty that it will never come to an end — it's likely the universe extends forever in space and will go on forever in time. Our results are consistent with an infinite universe."
    From: Scale of Universe Measured with 1-Percent Accuracy | Space.com
    Without wishing to overstate my case, everything in the observable universe definitely has its origins in Northamptonshire -- Alan Moore
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  5. #4  
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    Thank you Strange,

    It's good to hear that my thoughts go the right direction, so to say

    I will study the materials, you have sent me and will be back with some more questions about this (if I wont find the answers there).
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