health physics

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Assuming that at the beginning of time (big bang; creation of the universe) there
were equal numbers of U-235 and U-238 atoms produced, estimate the age of
the Earth (using terrestrial U-235 and U-238 abundances).

  • health physics -

    What does this have to do with health?

    Here are the numbers you need to solve the problem:
    U235 half life = T235 = 7.1*10^8 y
    U238 half life = T238 = 4.51*10^9 y

    Present value of the U235/U238 abundance 0.072 ratio =

  • health physics -

    i don't understand

  • health physics -

    What does this have to do with health?

    Here are the numbers you need to solve the problem:
    U235 half life = T235 = 7.1*10^8 y
    U238 half life = T238 = 4.51*10^9 y

    Present value of the U235/U238 abundance ratio = 0.0072

    OK. Now solve this equation for the "age of the universe", T

    (1/2)^(T/U235)/(1/2)^(T/U238) = 0.0072

    (1/2)^[T*(1.41*10^-9 -0.22*10^-9]
    = (1/2)^[(1.19*10^-9)T]= 0.0072
    Lake logs of both sides.
    [(1.19*10^-9)T]*(-0.301)) = -2.143
    T = ____
    Not a bad guess, but the actual value of the universe age is believed to be about twice as high.

    Creationism notwithstanding

  • health physics -

    My first answer was accidentally sent before completion. I hope you can understand the complete version that I just uploaded

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