Nick Nolte

You work at a job, and you reach a certain level, and you're a little satisfied, and you keep going at it a little more, and you finally finish it. You go, 'Ah,' all your dopamine receptor sites are full. You're satiated.

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.