Alastair Reynolds has a PhD in astronomy and has a background in space science — but the Terminal World author doesn't like to use the term "hard science fiction" to describe his work. Talking to Locus Magazine, he explains:
I'm always trying to write from a rationalist perspective, but I tend to push away from the label ‘hard SF' as well, because I think it's a limiting term that puts off as many people as it attracts. I try to position myself in the same area as Kim Stanley Robinson or Michael Swanwick, even though they've done things outside of science fiction. I'm not doggedly sticking to getting the physics absolutely right – I don't care about that. Style is very important. I'm not somebody who thinks that text is just there to serve the story. I'm trying to make it as rich and resonant as I can.
The fact that I've got a scientific background may be more of a red herring in my approach. I don't feel limited by saying I'm writing science fiction; I feel liberated by it.
Tons more fascinating insights at the link, and even more in this month's issue of the magazine.