David Mackay

As an astronaut, when you're getting ready to go out of that hatch, you know that's the pinnacle of both your career and your life. The view completely blows you away. The real challenge is getting past the excitement and getting focused and down to work.

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.