Sections Review

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cosmological principle cosmology homogeneous
Hubble constant Hubble law isotropic
Olbers' Paradox perfect cosmological principle

Review Questions

  1. What are the assumptions that Olber's Paradox is based on?
  2. Why is the night sky dark? What important conclusions can you draw from the simple observation that the night sky is dark?
  3. Will an object with a large redshift be far away or close?
  4. What can the Hubble constant constant (Ho) tell you about the age of the universe? How would the derived age of the universe change if Ho was 50 km/sec Mpc-1 instead of 100 km/sec Mpc-1?
  5. Is the Hubble constant actually constant throughout time? Why or why not?
  6. What would the relation between the radial velocity and distance be if there was no expansion? What would the relation be if the universe was contracting?
  7. Is there a center to the expansion in normal three-dimensional space? Why or why not?
  8. Why is an analogy like flat houses on an expanding balloon used to try to picture the expansion?
  9. Is the space between stars inside a galaxy expanding? Why or why not? Is the space between the molecules in your body expanding with the universe? Why or why not?
  10. How is looking at faraway objects equivalent to looking back in time?
  11. What is the cosmological principle? What is the perfect cosmological principle? Which one can an evolving universe fit in? Why?

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last updated: 26 May 2001

Is this page a copy of Strobel's Astronomy Notes?

Author of original content: Nick Strobel