When you have completed this chapter you should be able to: 1. Describe the Milky Way galaxy and indicate the sun's location in it.
2. Compare Population I and II stars.
3. Explain what a radio telescope is.
4. List the three ways in which radio waves from space are produced.
5. Distinguish between primary and secondary cosmic waves.
6. Explain what red shifts in galactic spectra indicate about the motions of galaxies.
7. State Hubble's law and use it as evidence for the expansion of the universe.
8. Outline the properties of quasars and what they suggest about the nature of these objects.
9. Discuss the big bang theory of the origin of the universe.
10. Explain what is meant by the big crunch and why the average density of the universe is such an important quantity.
11. Outline the chief events after the big bang occurred.
12. Explain the significance of the uniform sea of radio waves that fills the universe.
13. Outline the origin of the earth.
14. Discuss why other planetary systems are hard to find.
15. Compare the likelihood of interstellar travel with that of interstellar communication.