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A Question about the age of the universe

  1. Feb 15, 2017 #1
    Hello. This is my first post here. I have a question about the age of the universe that has been on my mind for the last few weeks. I have just read the posting guidelines and wish to state before I begin that I do not intend this as a challenge to mainstream theory but as an attempt to reconcile my thoughts with mainstream theory. I think I may be missing something here.

    The Big Bang theory has been widely described as "running the clock backwards" and coming to the conclusion the whole thing must have started from a singularity. If you run the clock backwards the universe is being drawn into a black hole, i.e., the singularity.

    Now a widely published description of falling into a black hole feet first describes a person as being torn apart by tidal forces as the gradient of the gravitational forces from his/her feet to his/her head becomes so great that eventually even the atoms are torn apart. This is the event as seen by an observer sufficiently removed from the black hole to not be drawn in themselves. However, for the person being drawn into the black hole the process would take forever. As the person approaches the event horizon time slows down due to relativistic effects and they approach the event asymptotically. They never reach the event horizon, although they do get torn apart.

    We as human beings living in the universe are not observing the event from outside. We are being drawn into the singularity if we run the clock backwards. So it seems to me that running the clock backwards and coming up with 13.7 billion years as the age of the universe fails to take this relativistic effect into account. The Big Bang must have occurred an eternity ago which is the same as saying that it never really happened.

    I have never seen this line of reasoning published anywhere. Is there a flaw in it? If so, what am I missing?
  2. jcsd
  3. Feb 15, 2017 #2


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    This is a misconception likely based on reading popular science. There is no black hole of this type in the early Universe. The rest of your post seems based on this misconception.
  4. Feb 15, 2017 #3
    The BB singularity is not the same as a BH singularity.
    The BB singularity is a singularity "of " spacetime, while a BH singularity, is a singularity "in" spacetime.
    Also both singularities are mathematical concepts where quantum effects apply and that represent where our current laws of physics and GR fail.
    Most all physicists today do not believe that there is any physical aspect to any singularity, and that perhaps a future validated quantum gravity theory, may reveal the nature of matter and spacetime at those levels.
  5. Feb 15, 2017 #4


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    What you're missing is a basic knowledge of the physics of cosmology, relativity and the big bang theory. Your post is based on (no doubt pop-science fuelled) misconceptions about all of these.

    If you are really interested in the universe, you have to do the hard yards and start learning some real physics.
  6. Feb 15, 2017 #5
    From the local frame of reference of the person falling into a BH, he certainly does just that, and his fate is sealed.
    From the frame of reference of a distant observer, he sees the person approaching the EH, time dilated, and being gradually redshifted along the spectrum until fading from view, and never actually seeing him cross the EH.
    According to the distant observer, and the person falling in, both their own perspectives as to what is happening, is as valid as the other perspective.
  7. Feb 15, 2017 #6


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    It's important to understand that black holes are a very massive, very dense (compared to the average density of space) region surrounded by a much larger much less dense region of space. This is not the situation when we run the clock backwards. The very early universe is extremely hot and dense, but there is no major difference in density anywhere in the universe. In addition, one must take the rapid expansion of the early universe into account. A black hole is not a region of expanding space, but the very early universe is.
  8. Feb 15, 2017 #7


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    Also importantly: the time coordinate typically used with the Big Bang theory is the time coordinate for a "stationary observer", so any effects of the density of the universe on time are taken into account automatically.
  9. Feb 15, 2017 #8


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    I'm not sure what distinction you're trying to draw here, but I think it's worth clarifying the actual difference between these two cases. A BH singularity is a future boundary (a spacelike surface with no events to its future) similar to the way the BB singularity is a past boundary (a spacelike surface with no events to its past). The difference (other than the time reversal) is that there is no horizon associated with the BB singularity--all timelike and null worldlines begin there. That is not true of a BH singularity: there are worldlines that end at the singularity, but there are also worldlines that do not (they stay outside the horizon and go to future infinity).
  10. Feb 15, 2017 #9
    Simply that spacetime evolved from the BB singularity, but your point, "is that there is no horizon associated with the BB singularity--all timelike and null worldlines begin there." is well taken.
  11. Feb 18, 2017 #10
    I want to thank all the responders. I see the flaw in my logic now.
  12. Feb 21, 2017 #11


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    I'd like to reinforce the point maroubrabeach already raise: the BB singularity may very well be nothing more than a mathematical artifact that has no physical meaning.
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