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Thread: Expansion Festival: Does Light decay and what about black holes?

  1. #1 Expansion Festival: Does Light decay and what about black holes? 
    Forum Cosmic Wizard icewendigo's Avatar
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    As part of the Expansion Questions Festival, I had a couple of questions, Ive red, I mean Ive read that theres a red shift in distant galaxies which supports the expansion idea, and wonder if light can shift over millions of years, as if it decayed into red or lower frequencies? Hum I guess not because gamma rays I think can come from distant galaxies(unless there was more of it when it was initially emitted?).

    And Im puzzled by the expansion from what appears to have been a gigantic black hole, why did the universe expand from a black hole ish state and why doesnt the black hole expand the same way (unless the black hole does expand in an unperceived dimension?) ?


    And in the expanding balloon analogy, there is no center of the universe from the surface perspective, but the balloon universe is expanding from the perspective of a central point outside the 2 dimensions of the ballooniverse a point outside the ballooniverse only perceived from another/extra dimension.


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    Brassica oleracea Strange's Avatar
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    This sounds like a version of "Tired Light"; there are all sorts of things wrong with this. But one biggy is the fact we don't just see red shift but we see other effects of time dilation (strictly, scale factor change) such as supernova light curves. I think it can be considered well falsified.
    Tired light - Wikipedia, the free encyclopedia

    As for the second part, the universe didn't arise from a black hole. I'm not sure where you got that from.


    ei incumbit probatio qui dicit, non qui negat
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    Forum Cosmic Wizard icewendigo's Avatar
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    But if "everything" was in a tiny area, wouldnt that be similar to the biggest black hole there ever was? Billions of stars worth of stuff in the same place, the gravity must have been mind mindbogglingly gargantuan?
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    Brassica oleracea Strange's Avatar
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    Quote Originally Posted by icewendigo View Post
    But if "everything" was in a tiny area, wouldnt that be similar to the biggest black hole there ever was?
    I don't have the theoretical background to fully answer this (Speedfreek?) but I think it is the difference between a sufficiently dense "lump" of matter somewhere in the universe, which would form a black hole, and the universe itself being hotter and denser than it is now.
    ei incumbit probatio qui dicit, non qui negat
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    Brassica oleracea Strange's Avatar
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    Quote Originally Posted by icewendigo View Post
    And in the expanding balloon analogy, there is no center of the universe from the surface perspective, but the balloon universe is expanding from the perspective of a central point outside the 2 dimensions of the ballooniverse a point outside the ballooniverse only perceived from another/extra dimension.
    The important point about this analogy (as with all analogies) is that it has limits. The surface of the ballon is a 2D analog for the 3D universe. That is it. End of analogy. If you start talking about the 3D balloon or the gas inside it or the ribbon tied to it, then you have taken the analogy outside of where it is valid.

    There is, as far as we now, no "higher" dimension that the universe is embedded in.

    Someone did once suggest that you could consider the radius of the balloon as "time" in the evolution of the universe (i.e. the past balloon-surface is inside the current one). Doesn't work for me, but some people liked it.
    ei incumbit probatio qui dicit, non qui negat
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    Forum Ph.D.
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    the way i understood it, there wasn't 'everything' present in the beginning. but a high enough state of energy to start it off and to keep it going.
    helium or ion didn't exist at the big bang and took quite a while before it did for example. you know, like one thing led to another.
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    Quagma SpeedFreek's Avatar
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    Have a look at this:

    Is the Big Bang a black hole?

    It is a little too long to summarise.
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