| What theories of stellar energy generation were current in the 19th century? Why were they inadequate? | [3] |
| Describe 19th and early 20th century theories of stellar evolution, relating them to the then-current theories of energy generation. Discuss the problems posed for these models by Eddington's results on the mass-luminosity relation and the Hertzsprung-Russell diagram of stellar clusters. | [3] |
| Explain how advances in theoretical and experimental physics in the period 1900-1940 led to the correct explanation for stellar energy generation. | [4] |
| [2007 Q5.] |