1. All the moderators mentioned in this chapter to slow down neutrons are light nuclei. Why are light nuclei used for moderators instead of heavy nuclei?
2. Why is ?ssion fuel placed in 4-m-long rods placed parallel but separated, rather than in one lump of mass?
3. Discuss how each of the following sources of energy is ultimately derived from the sun: wood, coal, gas, oil, water, and wind.
4. Why does a star's temperature increase as fusion proceeds? Why are higher temperatures required for the carbon cycle than for the proton-proton chain?
5. The fusion process continues in a very massive star until its core consists of nuclei near 56Fe. Explain why this occurs.