hw1 - Physics 3002 Problem Set 1 due Lam Hui 1 In class we...

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Unformatted text preview: Physics 3002 Problem Set 1, due 2/4/09 Lam Hui 1. In class, we discussed several ways in which the Olber’s paradox can be resolved. In our universe, it turns out the resolution is mainly through the finite age of the universe. This is actually discussed in Ryden section 2.3. Let’s make sure you understand the arguments. You could easily copy the answers to the following questions from the book. Well, don’t! Try to do the math yourself. a. Given that the age of the universe is about H- 1 where H = 100 km/s/Mpc, what is the furthest you can possibly see (in Mpc)? b. We know from observations that the luminosity density (i.e. energy per unit time per unit volume) of galaxies in our local neighborhood is nL ∼ 2 × 10 8 L circledot Mpc- 3 . Here, luminosity is measured in units of the luminosity of the Sun L circledot . Let us assume this luminosity density is constant, independent of both position and time. What is the total flux we can see from all galaxies in our observable universe (integrated over all directions in the sky and to the furthest...
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