Short Questions about Cosmology

  1. The Cosmic Microwave Background was as bright as a star: a blackbody with a temperature of 3000 degrees K.

    a) Discuss the similarity between the photosphere of a star and the Last Scattering surface at redshift 1000 where the Cosmic Microwave Background was generated.

    b) Why is the Cosmic Microwave Background not as bright as a star today?

  2. a) In the very hot early universe there were as many protons, anti-protons, electrons and positrons (anti-electrons) as photons. Where are most of the protons, anti-protons, electrons and positrons now?

    b) Why is there anything left now? eg. Why is there matter?

  3. Under what conditions is the expansion age of the Universe the same as the length of time since the Big Bang?

  4. What is meant by the statement that the surface of a ball has no center?

  5. Why does the CMB look like a 2.73 K blackbody when it was emitted by material that was 3000 K?

  6. How can globular clusters be used to place a lower limit on the age of the Universe?

  7. Why were no heavy elements produced in the Big Bang?

  8. a) Explain why an open universe (one that will never collapse on itself) is expected to have less matter in it than a closed universe (a universe that will eventually stop expanding and collapse).

    b) The age of the universe is roughly one divided by the expansion rate now: one divided by the Hubble constant. The true age is less because the universe was expanding faster in the past so the average value of one divided by the expansion rate is less than it is now. Would you expect an open universe to be younger or older than a closed one and why?

  9. a) Describe the advanced stages of closed and open universes: the long term fate of the universe in each case.

    b) Which do you find more appealing?