One of the big questions at that time was — what is the strong force, one of the four basic forces, the most powerful force of nature, that among other things holds atomic nuclei together? There were lots of known facts about the strong force, but no real theory. Freeman Dyson had said that it would be 100 years before it was understood.
Now I'm rather curious about the novel that he has been writing. It sounds like a totally new angle for a mystery genre.