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Thread: CMB in the past

  1. #1 CMB in the past 
    Forum Freshman
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    Nov 2007
    San Diego, California
    Just had a thought about this that I haven't heard anything about before so I gotta ask. The CMB is the remenance of the surface of last scattering, but just after the universe became transparent this background radiation was all gamma rays. As the universe expanded, the radiation streatched into x-rays, and then UV. On its way to being microwaves, there would've been a period where it's peak went through the visible spectrum. Assuming there were creatures with eyeball like ours back then (I know, big assumption), what would they have seen? Would the sky (even night) just be blinding?

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  3. #2  
    Anti-Crank AlexG's Avatar
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    Mar 2012
    I don't think it would be limited to the sky. The CMB does not just exist very far away, it exists right here as well. I believe the current estimate is that there are about 400 million CMB photons in each cubic meter. If this was in the visible spectrum, I'd guess we'd see everything in a faint, ever present glow.

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  4. #3  
    Forum Freshman Schrodingersothercat's Avatar
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    Oct 2011
    Now in Glendale AZ but formerly from Elkhorn WI, just outside Milwaukee.
    Would this transition from one state to the next be instantaneous in a given area? Meaning, would each transition from one state to the next happen in a specific region of the universe and then radiate out to the farther reaches of the universe so it would appear as a wave from a thearetical observer at the edge of our universe? Or would the whole universe reach each next state universe wide so, to that same observer, it would seem to change like a light switch being flipped? Plus how long would these different states last until the next state came into existance?
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  5. #4  
    Quagma SpeedFreek's Avatar
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    Jan 2011
    London, UK
    The CMB had a temperature of around 3000K when it was emitted, which puts it firmly in the visible spectrum when it was emitted. It was never gamma rays or x-rays, it started out at 3000K (visible light) and has cooled to 2.7K (microwaves).
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  6. #5  
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    Jul 2012
    I don't know much on the subject but I would think so.The reason we can't see radiation is because it is beyond our spectrum of visible light. It could be a glow, or it actually might be a a flood of dots depending on what planet the hypothetical creature lives on, the sharpness of eyesight relative to our own, and the star type, velocity, orbit, axis tilt, and distance to stars which may effect the eye's ability to detect the neutrino particles blasting across the planet by trillions per second.
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