[int_19h]

They get to invent as many "impossible" things as they want, really. But they all need to have plausible-sounding explanations (given our current level of scientific understanding), and they need to act in a consistent, predictable manner, including consistency with known laws of nature - e.g. if you have antigravity, the default assumption is that it obeys the inverse square power law, and if it doesn't, that needs to be called out and have some explanation of its own.

[ethbro]

I'd hew closer to TeMPOraL's definition.

On the one hand, one obviously needs some technological leeway to write a fun novel set in the future.

On the other, if every roadblock is responded to by suspending scientific treatment, it doesn't seem like that's a good faith "hard" effort.

I think Ringworld is instructive. The Wikipedia article specifically calls out technical inaccuracies in the original... inaccuracies Niven specifically made an effort to patch up in later books.

So the count of intentional lapses seems as decent a proxy for hardness as anything else.

[int_19h]

I would consider Ringworld to be borderline hard sci-fi, but precisely because it has some reasonably sounding explanation for his technomagic. E.g. the General Product hulls - them being a single macro-molecule is a reasonable pop-sci explanation for their properties, even if the book doesn't explain how such a molecule is made. Does that count as an intentional lapse?

[stevenhuang]

What are your thoughts on Diaspora? (Greg Egan)