Herbert Hoover

A lot of people give actors credit when they gain weight for a role in a drama when they win an Oscar, but when you're doing a sitcom, people don't give you a lot of credit, because you've got to keep your weight on for five or six years if it's successful.

The historical novelist has to consider what has actually happened, while the SF writer is dealing in possibilities, but they are both in the business of imagining a world unlike our own and yet connected to it.