Lecture 31. Dark Matter, Misc., & Cosmology

Lecture 31. Dark Matter, Misc., & Cosmology

A. Class Business

  1. Review topics*, on main web page

  2. Readings list*, also on main page

  3. Homework 6. questions after this lecture

  4. Homework 6. due at end Friday morning's class --

      NO LATE WORK ACCEPTED:
      solutions posted IMMEDIATELY after class


B. Dark Matter

Q: How is mass in the Milky Way distributed?






C. Quasars -- Quasi-Stellar Objects (QSO's)














D. Cosmic Microwave Background (CMB)

Q: Recall that all objects above absolute zero radiate as blackbodies. How does the universe radiate?

Q: How did it get so cold? (or: so warm?)



  • HINT: When gases EXPAND freely, they COOL

  • Why? The total energy in a gas is depends on
    1. amount of energy each particle has (= speed = temp.)
    2. total number of particles.
    If you take a WARM gas and spread its energy over a large volume, the resulting diffuse gas is COLD.

  • (few % of snow "in between" TV channels is CMB)





    E. Cosmology