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Thread: Age of universe and effective receding speed in sync?

  1. #1 Age of universe and effective receding speed in sync? 
    Administrator KALSTER's Avatar
    Join Date
    Sep 2007
    South Africa
    How is it that the point at which the effective receding speed of galaxies approaches C and the origin of the oldest light to reach us possible is the same? I mean, the big bang occurred about 13.7 BY ago so in an expanding universe (with an inflation period with effective receding speeds exceeding C) the oldest light we would be able to see would be light that originated from a source 13.7 BLY away. But I don't see a reason why that source would also coincidentally be receding at C?

    Let's say for a moment that the universe is 100 BY old. In such a universe the farthest sources of light we would be able to detect would also be at the point where the effective receding speed reaches C, no? We would not be able to see farther, because the light would be red shifted into oblivion due to expansion, no? Similarly in a way to a light source that is approaching an event horizon. The closer it gets, the more red shifted it is until it is beyond the possibility of detection at the border of the event horizon.

    Why do these two restrictions line up? Are they dependant on each other in some way, or did I simply make a mistake?

    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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  3. #2  
    Join Date
    May 2008
    The distance to the edge of the universe is worked out using various yardsticks. Type1A supernovae (which are not standard), quasars, etc. That gives 13,700 million miles as the furthest thing.

    You have 186,282 mps for light speed. The furthest we can see is 13,700 million light years. So, you divide 186,282 by 13,700 which gives you 13.597. That means for every one million light years, the universe is expanding almost 14 miles per second. The Hubble constant.

    The problem is that all we have is a "snapshot" of decades out of billions of years. I can see for maybe five miles from my house on a clear day. Yet on a misty morning, my vision may be limited to (say) a mile so if I never left my house and knew no better, with just that one "snapshot", I might think the world ended just one mile away from my house.

    Of course, the haze is where I am but is too diffuse to see close up. Only distance makes it visible and that may be true for the CMB. We have untold trillions of stars giving forth all sorts of radiations and particles for untold billions of years and that EMR and material does not just vanish. Who is to say that it does not create a distance haze? Strangely, the CMB is at 2.7K, the same temperature as space close to us and not 3,273.K as it should be after the big bang.

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