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(a) Calculate the approximate age of the universe from the average value of the Hubble constant, $H_0 = 20\textrm{ km/s}\cdot\textrm{Mly}$ . To do this, calculate the time it would take to travel 1 Mly at a constant expansion rate of 20 km/s. (b) If deceleration is taken into account, would the actual age of the universe be greater or less than that found here? Explain.
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  1. $15 \textrm{ billion years}$
  2. If deceleration has occurred, the average velocity since the beginning of time must be higher, in which case the time is less. The universe would be younger than calculated in part (a).
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OpenStax College Physics for AP® Courses Solution, Chapter 34, Problem 8 (Problems & Exercises) (2:57)

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