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Dark corner of the universe

  1. Dec 17, 2012 #1
    Dark "corner" of the universe

    Hi all,

    So I'm reading about special relativity and "c" and, go figure, I have a couple questions. But here's my first, most basic question. Forgive me for confusion of terms and noob questions.

    I don't know "when" light was created (at BB or much later), but let's say that - if I can - that the very first photon, Photon Bob, started traveling at 'c' at 'second 0' and that we're in the vacuum of our universe without any gravity to bother us.

    Apparently, light (this photon) travels at 'c' - 299,792, 458 metres/second. So, at Start time (Second 0), location of Photon Bob is at x 0, y 0 And it is traveling solely in the direction of y. So at End time (Second 1), Photon Bob is at X 0, Y 299,792,458 metres.

    My question then, is WHAT, at that exact instant, Second 1, is at 299, 792, 459 metres? More space - space where light hasn't reached yet?

    Sorry, I have no familiarity with physics/math notations to have made this shorter. But I really appreciate the help!

    - Hypo
  2. jcsd
  3. Dec 17, 2012 #2


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    Re: Dark "corner" of the universe

    The big bang occurred everywhere in the universe at the same time. The very early universe was filled with an extremely hot bath of hot particles and radiation, annihilating with themselves to make more particles and radiation over and over again. The key thing to understand is that there was no "empty space" anywhere in the universe at this time. The entirety of the universe was filled like this.
  4. Dec 17, 2012 #3
    Re: Dark "corner" of the universe


    I'm confused b/c I'm reading "The God Problem" by Howard Bloom and he translates into layman's terms one of Einstein's findings that 'c' is a universal "speed limit" - nothing exceeds c.

    But if speed is measured by distance/time, what is the location at which anything traveling at c will be located 1 unit of time later if it's already at the "sidelines/edge" of the universe and heading "out of bounds"?

    However, it sounds like you're saying that, apart from black holes, there is no part of the universe that is "dark", including the expanded areas that weren't there when the universe was smaller?

    Sorry, this is confusing stuff! Appreciate the help!
  5. Dec 17, 2012 #4


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    Re: Dark "corner" of the universe

    That's actually not true. The speed limit c is only for local areas of space where you can apply Special Relativity. General Relativity has no such limit and it is this fact which allows for galaxies to recede from us at a velocity greater than c due to cosmological expansion.

    I'm saying that there isn't any "expanded areas" of the universe that wasn't there prior. That whole idea is incorrect. The universe is not expanding into anything else. Space is not being created where no space was before. Everything in the universe simply gets further away from everything else unless bound by gravity or another fundamental force like electromagnetism.

    See the FAQ threads in this forum.
  6. Dec 18, 2012 #5
    Re: Dark "corner" of the universe

    Very interesting. Appreciate it, Drakkith!
  7. Dec 23, 2012 #6
    Re: Dark "corner" of the universe

    When you see descriptions about the big bang [BB]occurring at some 'point', they are referring to the observable universe, not the total cosmos. [I just saw an illustration in Wikipedia a few days ago, cannot find it now..]

    'Dark' likely refers to the fact that until about 380,000 years after the BB no light could get through the initial charged plasma...photons [particles] of light were absorbed. So we could not 'see' anything had we been there.

    At the BB and until some 380,000 years later, things were initially really dense....and very different from today.....so much so that at the BB itself nobody knows exactly what was there....nor where it came from......our models actually start just moments after the initial bang.
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