Age of Universe, Redshift & Scale Factor

Discussion in 'Astronomy, Exobiology, & Cosmology' started by kingwinner, Apr 2, 2007.

  1. kingwinner Registered Senior Member

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    Assume that the current age of the universe is 13.4 billion years old, and that we live in a matter-dominated, omega_m = 1, critical universe, what is the age of the universe at redshift 0.6? HINT: use the current age of the universe to pin down the proportionality relationship between age and the scale factor


    Some formulas that I have found are:
    1+z=R(t_o)/R(t) (redshift and scale factor)
    H_o= cz/d (hubble constant)
    omega_m=1 means k=0 and matter-dominated together with k=0 critical universe implies that the age of the universe t_o = 2/(3H_o)
    For k=0 critical universe R(t) is proportional to t^(2/3)


    I know that (t_o) proportional to (1/H_o) proportional to (1/z), but I don't know how to connect this with the scale factor...and I have no idea how to "use the current age of the universe to pin down the proportionality relationship between age and the scale factor"


    Can someone please help me out? I did all the reading but was still unable to solve this problem, no matter how hard I tried...

    Thanks for helping!
     
    Last edited: Apr 2, 2007
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  3. kingwinner Registered Senior Member

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    I am not too sure where to post because this is related to astronomy, but it's also atsroPHYSICS
     
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  5. Singularity Banned Banned

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    Let me givya hints for blowing the whistle on Age of the Universe.


    1) Oldest objects are 15 billion light years away. So how fast did they go away from us since the big bang ?

    Definitely not at light speed. And


    2) how further away did they go away in that period since we see the light from its 15 billion years old position ?

    Definitely the objects are not at the visible positions right now since they are traveling apart so fast.


    3) How much universe is behind us from that point, ie. if we face that object and turn behind then how much back can we look ?

    Definitely more than 15 Billion Light Years (BLY). And


    4) whats the distance between the two most distant object from us ?

    So A object is at 15 BLY from us and B is 13 BLY , so the distance between them = ?


    5) How do u justify age of the universe to be 15 billion years since it mustav taken trillions of years for object to go that far apart.

    This is depend on the acceleration of the expansion of universe ie. we have to decelerated the expansion as we go back in time.

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