DOMAIN vs HIERARCHY
I understand where Michael K. is coming from when he understands these as hierarchical or a progression of relaxed to ever tightening requirements. I see these tags as three separate domains of inquiry, rather than a hierarchical structure of inquiry, and that any one or more than one can be applied to a query.
- A reality-check asks simply "does this sound reasonable"; "does this make sense". No particular framework of reality is suggested or assumed.
- A science based question asks for an answer with scientific foundation.
- A hard science question asks that answers contain appropriate scientific data a/o citations to back it up.
All three of these tags describe the nature of the response: what it should look like, how much research should go into it, how detailed and technical the answer has to be. What none of these tags seem to do is describe the nature of the query or better the nature of the object of the query.
I do not see these as being hierarchical.
- Hard science does not assume science based. The domain of this kind of answer is providing examples of data, equations, journal article citations, etc. that either support or deny the object of the query.
- Science based does not assume reality check. The domain of this kind of answer is providing general scientific principles and how they might apply to the object of the query.
- Reality check is not the bottom rung of the ladder. The domain of this kind of answer is that of common sense, ordinary logic, pattern matching, error teasing.
To use the unicorn as an example, in combination with the nature of the tags themselves, I'll show how I think these tags can handle any kind of question. First, I'll assume that we agree that dragons (e.g. Smaug) and unicorns (fairy stories) do not exist on Earth as depicted.
So if someone asks the question "I think narwhals are cool. Would it make sense for a horse-like animal to grow out a long tooth?, which later humans will confuse for a horn (< Lat. cornu, horn) --- thus, a unicorn!" I think any of the three tags could apply:
- The reality check tag would seek an answer like "Yeah, seems plausible given that the world you're describing has similar beasts derived from mythological sources. You already mentioned narwhals, so why not horses too?"
- The science based tag would seek an answer like "The narwhal tusk is an elongation of the left canine tooth that protrudes through the animal's lip. Horses do have canine teeth. Because the evolution of the tusk is reasonably well understood (descent from a toothed artiodactyl, placement & growth of the tusk within the skull allow for positive identification), we can at least posit a potential scion of an early equid developing similarly."
- The hard science tag would seek an answer like (and I'm just making this up, because I'm not a paleobiologist) "I read in PaleoBiology This Week about a now extinct form of water deer (Hydropotes antiquus) the right canine of some specimens having been found to be considerably enlarged and twisting with a slight helical twist and that the left canine is diminished in size. There is evidence, according to Dr. Li Hsien, that these early cervids used their elongated tusks for dominance display as evidenced by bony scar tissue around the muzzle area of male H. antiquus."
I disagree with M.K. as regards Using more than one of the above tags on a single question however doesn't seem to me to make sense in any situation.
I don't see any issue with using one or more together, because 1) they're not asking for the same thing; and 2) I don't view them as a hierarchy! (I would agree: if they were hierarchical in nature, then Reality Check would be the basic form; Science Based would subsume a positive reality check; Hard Science would subsume the assumption that the answer must be based in known science.) If the querent had placed all three tags, then the respondent would simply be required to provide, basically, all three types of answers!
- As to the Reality Check, ABC; as to the Science Based, PRS; as the Hard Science, XYZ.
In contrast, had the query been about dragons (as seen in the Hobbit), then we can still answer the question given these tags, though likely with different results. The reality check would most likely be positive, as dragons only have to make sense within the setting or world in which they have been posited.
A Science Based query about dragons can certainly be asked and answered. In the history of Earth, there have been enough large beasts to demonstrate that size is not at issue. Some animals have scales & feathers, so those features of dragons should pose no difficulty. No known animal breathes fire, but since we're not required to provide scientific data, and whether or not magic & pseudoscience work in that world or setting, we can at least offer sound scientific speculation as to potential mechanisms for fiery breath. A bold respondent may even posit an in-world scientific answer (that accounts for magic as a natural force, if enough data is known).
A Hard Science query about dragons will, of course, run into a wall. Big beasts, sure! We know about dinosaurs. Scaly or feathery beasts? Sure! We know about dinosaurs. Fire breathing beasts with four feet, two wings, tough scaly armour and perhaps decorative feathers? Nope. No such thing known; no way for it to be able to fly. The Hard Science answer will be along the lines of "What-if speculation aside, there is no way for known to biology or physics or chemistry to allow for the particular combination of characteristics you want in your dragon; so the answer to your question is NO."
- Should hard-science always imply science-based, without that having to be made explicit? --- NO. I think it's clear there is no implication.
- Should science-based always imply reality-check, without that having to be made explicit? --- NO. Same: no implication.
- Does it ever make sense to use more than one of these three tags on a single question? --- YES. The three tags can validly be used in combination. Should they be so used is a different matter!