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Homework Help: Age of The Universe!

  1. Mar 30, 2010 #1
    Hi all,
    Hoping you can help with this problem!

    1. The problem statement, all variables and given/known data
    For a flat universe, show that [tex] t_{0}=2/3 (H_{0})^{-1} [/tex] ? Seems like a simple problem I just don't really know where to start.

    2. Relevant equations
    Hubble's law [tex] v= H_{0}r [/tex]
    and then [tex] t= 1/H_{0} [/tex]

    3. The attempt at a solution
    I just need guidance where to start. Flat universe means that expansion is constant in any direction right? What do I do?
  2. jcsd
  3. Mar 30, 2010 #2


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    Science Advisor
    Homework Helper

    flat universe means the hubble constant is constant.

    Then 1/hubble constant has units time.
    Think of the equations for something that doubles/halves with a constant time interval
  4. Mar 30, 2010 #3
    How about the kinematic equation: x(t)= vt + 1/2at^2
    Not sure if this is right and what to do with it? maybe take a derivatives of both sides???
  5. Mar 31, 2010 #4
    I still can't figure out the answer, can someone give me a hint please
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