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Evaluating the age of a universe

  1. Sep 12, 2008 #1
    I need help evaluating the age of a universe. Using a graphed representation of hubbles's law.
    The recession velocity is on the y axis, and the x axis is in billions of light years. How can I approach this problem?
  2. jcsd
  3. Sep 14, 2008 #2

    Vanadium 50

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    The key to your problem is that the Hubble constant has units of inverse time. The age of the universe is then roughly 1/H0. You need some detailed calculations to determine that the 1 is in fact 1 and not 2/3 or 3/2, but you can get a remarkably good estimate by simply using 1.
    Last edited by a moderator: Sep 14, 2008
  4. Sep 14, 2008 #3
    I'm not understanding why my post was pulled. It contained some information that is debatable... but I wouldn't think it was material to just be pulled without discussion.

    PLUS I said some very important things. Like the fact that we don't even know as of the last decade whether something is 6000 or 10000 LY away. How then would we necessarily be very accurate in estimating the distance of things billions of LY away? It's a self-supporting philosophy to some degree. Please review my post in the blue shift thread where I perform calculations to show that the norm in a local system of 10 million LY would be that every galaxy would be moving rather quickly towards each other. Well I just did a quick qualitative calculation but anyway... it makes the point that all things in such an area would be 100% blue shift. WHY then...the lack of blue shift objects save a few on our observations? -Bob
  5. Sep 14, 2008 #4

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    You'll have to ask the moderators why it was pulled, but I suspect it was at least partially related to the fact that it didn't answer the OP's question but instead went off on a speculative tangent.

    Whether there is or is not uncertainty in the distance scale is irrelevant to the OPs question. His question was on the technique. The technique is what it is, irrespective of the actual values plugged in.
  6. Sep 15, 2008 #5
    He asked as though he thought this was a formula for *actually* calculating the age of the universe. A lot of people are naive. They think that by just taking a formula offered, you get the ACTUAL ANSWER.

    And I'm just asking things like "If this whole big bang model is correct, then why is M31 moving PAST M33 towards us? I mean if you do the calculations M31 at some point was MORE distant, a few billion years ago. "

    See these kinds of things right in our own local system with M31 2 million LY and and M33 3 Million now... they just don't jive because are we not the primary source of gravitational pull on M33 along with M31?"

    I was just saying..there are questions. It's not all nailed down in a nice package where you can just plug numbers in and get a reliable answer.

    The uncertainty about distances is important to note *because* many people who are novices think that we can reliably triangulate on things billions of LY away :-). And thus they are under the impression that it's really SOLID science that these red shifts are truly correlated to distance with some precision. Anyway..for what it's worth. -Bob
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