I’m curious. Greg Johnson over at SF Site doesn’t deserve to be singled out, but in his review for Al Reynolds’ Zima Blue he says ‘Hard science fiction, and space opera, are styles of SF that tend to work better at lengths longer than short stories’. I’ve just edited a volume of space opera stories, and have another that contains some hard sf and space opera stories coming shortly, and they’re all short stories pretty much, and I’ve heard this view before, but is it true?  I do think the novella may be the best length for science fiction, but wasn’t science fiction founded on the short story? If you run through Bob Silverberg’s The Science Fiction Hall of Fame, isn’t it filled with short stories? And, aren’t a lot of them hard SF or space opera?  When did it become popular wisdom that sf works better at longer lengths? And why? Is there something that we were doing, back in the 40s, 50s, and 60s, that we’re not doing here in the Oughties?