Hard Science Fiction Guide

This is where things get a little weird. (-er)

The category of so-called “Hard Science Fiction” (HSF) is a difficult beast to nail down accurately. Some folks consider that any story containing any possible element suggesting FTL travel in any mechanism automatically makes a story fantasy. (I know prominent editors who expressly state such things in their publication requirements, for instance.) For them, anything that cannot be immediately explained by our current understanding of science is unacceptable.