SciFi & Fantasy Hardness Scale

There are hardness scales that can be used to categorise a fictional work or, in our case, one of our worlds. Even a casual observer might note that some SF works are basically fantasy set on a weird, often monoclimatic, planet; whilst others pay very close attention to deep physics and mathematics; and finally are those that simply admit no handwavery or any kind of unobtanium whatsoever. Other genres, particularly fantasy, could also be graded on such a scale, though at a spooky twist in axis. A classic scale in this genre is the magic hardness scale. It's just like the science hardness scale, only not.

I made one that relates various schools of worldbuilding to hardness factors (H) and noted which tags might be a good fit for any given question.

Realist School:

•   8. Real World. All the constraints of the real world with no hint of futuristic or speculative engineering & science. Fiction & drama with real science, real science based detective stories, etc. Apollo 13.
•   7. Just a Matter of Engineering. Real world science compliant with perhaps some fudging of the engineering. Alternate reality spun from super new discoveries. Near futuristic action thrillers. The Martian.

Alternate History School:

•   6. One Main Change. Basically a playground for what-if SF. "What if a nearby star explodes..." sort of thing. Greener Than You Think.

Rigorist School:

•   5. New Science. This is where the maths and science kids play, coming up with cool ideas and applying them realistically. Leans more towards real world science. Ordinary scifi. True Story, Frankenstein, Space 1999.
•   4. World of Gadgets. This is where the maths and science kids let it all hang out. Leans more towards laxer perspective on the science. Ordinary scifi. Willard Phule books. Sector General.

Fantastic School:

•   π. I Don't Care How it Works! Here is where real science takes a back seat to pseudoscience and speculative science. Worldbuilders here tend to focus on science as decoration and setting material rather than functional bits and bobs. Star Trek
•   3. Magiscience. Moving further away from actual science and into the realms of fantasy. Star Wars
•   e. Forget the Science. Rule of Cool is in effect! We've now almost completely divested ourselves from actual science. Various mystical and magical elements become prominent. Soft Fantasy could be here; as well as Science Fantasy; perhaps even the various -punk genres. Think Space Balls. And PJO. And Red Branch, etc. Worlds collide.
•   2. Where's the Magic? This is where science really just get ignored. We've moved from the softer magic systems to harder, mode codified ones. Basically, we're heading along an inverse of science here. Think D&D, Conan the Barbarian, Ultima Games, etc.

Irrealist School:

•   U. Backroads of Memory: This is the realm of Faerie. This is where the hardness axis needs some serious chiropractic care. There are things. People are here. Things happen. Perhaps. No amount of science can explain, though it seems like it should ought to can do that, so it usually just sits on a tuffet with its bowl of cold curds and whey. Things don't make always sense, but they work. Call it superscience, call it magic, call it divine power, or super power. Lord of the Rings.
•   √i. Unreal Is the New Real!: Here is pure fantasy. The only rules that matter are the ones that --- oh, wait! No, this is just chaos! Internal consistency? We don't care! Science based? No thank you come again! Pfft. We don't even care about the magic systems any more! Discworld, Dark Crystal.
•   ⊥. Through the Mirror and Back Again: Here is where Reality gets eaten for dinner by tomorrow's lunch. Nothing makes sense. Everything weirds. Heck, weird seems perfectly normal here! £sd is the sovereign cure for this trip. This is where magic licks its finger and sticks it in the ear of real world science, because the scale has now passed through reality, taken a sharp turn at againreality and is now jumpscaring reality from the other side. Through the Looking Glass would be a very tame example. Some mystical fantasies, visionary encounters, psychedelic adventures, some spiritual and perhaps legit religious works might find a place here too.

I would argue that hard-science fits H8 and H7 the best, as these really involve only actual science with known facts, equations, values, etc.

Either hard-science or science-based could be used with H6. If the one main change is something that we know about --- a large asteroid striking the Moon --- then we've got the relevant data and the equations and can extrapolate how much shit will hit the fan to at least fourteen decimals!

The science-based suits H5 and H4 perfectly for most questions. An occasional hard-science tag might come along, though.

We don't have a tag that would really be suitable for any H value from Hπ and below. I would argue that something like the science-based tag but tailored to pseudosciences or alternative sciences would work fine as they would be based on principles stated by the worldbuilder:

For questions that require plausible (better than suspension-of-disbelief) answers based on the science, mythology, witcraft, or magical lore of your world. In a continuum with with but also contrasting with the science-based and hard-science tags; this tag is most appropriate for fantasy, science-fantasy, and internal-consistency queries. This tag may not be used alone. This tag may not be used with the science-fiction, fantasy, hard-science, or internal-consistency tags.

We might even posit a tag for the more unreal worlds. Perhaps an irrealia tag.

For questions that require off the wall, out of the box, and sideways thinking. Irrealia are things that are not real, not even possible in the real world. This tag is for the division by zero worlds that still require sane but zany answers.

The linked query: I would argue that the linked query has a hardness value of H4, putting it in the World of Gadgets. The graviton drive is basically a sciencey sounding gadget, making it similar to warp drives, transporters, light sabres, etc. It's too soft on the scale for the hard-science tag. A science-based tag would be more appropriate for this query.

Those tags do not identify a genre

And that's incredibly important!

Unlike almost every other tag on Main, which scope the question, the science-fiction, science-based and hard-science tags scope the answer. They identify how much effort the respondent should be putting into justifying their answer is correct.

hard-science answers must prove beyond a shadow of a doubt that they are correct using current science. Using this solution would not incur the wrath of any practitioner of the art.

Can my FTL design actually exist? NO. There is no science that supports it's eventual engineering.

science-based answers needn't prove they're right, but are expected to use current science to rationalize a solution. "Speculative science" falls within this scope. Using this solution might incur some wrath from practitioners of the art, generally those who believe everything should be hard-science or fantasy, or perhaps those who are basing their next research funding grant on an opposing theory.

Can my FTL design actually exist? POSSIBLY. There are mathematical models that suggest that the design can be achieved even though there's no science or engineering that tells us how to build it. So, use it at will, but we recommend avoiding details about how it works.

science-fiction answers are more artistic, almost technobabble, using science as the springboard for a more fantastic solution that meets the expectation of suspension of disbelief. Answers are more along the lines of the "what if?" thought exercises that embrace the possibility of today's science being incomplete or simply wrong. Using this solution without a great story behind it is almost sure to cause MIT students to chant something like "The Ringworld Is Unstable!" at some Comic-Con convention.

Can my FTL design actually exist? YES! In your imaginary world it CAN exist and has enough science behind it to make the world fresh and enjoyable even though a quick Google search will demonstrate the science doesn't actually exist.

In the end, it's the post owner's choice to use one or the other of those tags and how the choice is made depends on the kind of information they're looking for in the answers. If we, members of the community, think the tag choice was inappropriate, that's the purpose of comments (asking if a change is appropriate). We shouldn't be making arbitrary changes unless we're sure a mistake has been made (such as removing internal-consistency because they didn't read the wiki, aren't following the wiki's rules, and aren't asking an IC question... I always leave a comment explaining why I removed it).

And a quick summary of the internal-consistency tag's history

Once upon a time there was a tag named "reality check." The intent of that tag as explained in its wiki was to test the reality of a worldbuilding idea against the existing rules of that imaginary world (sound familiar?). In other words, the "reality" was that of the OP's imaginary world and the check was against that fictional reality, never the Real World.

But, since people don't read tag wikis, it was inevitably (and most often) used to ask questions along the lines of "here's my ridiculous idea, can it exist in the Real World?"

The abuse was so bad that I had a lengthy discussion here in Meta, the result of which was renaming "reality check" internal-consistency, even though there were a bazillion questions for which the tag no longer made sense (they were mis-tagged in the first place, but people who don't read wikis didn't realize that).

The abuse has dropped considerably. The reason it's exclusive to the "science-" tags is that it has one very specific purpose and a whole set of just as specific rules that go with it. One cannot have an answer scoped by the "science-" tags to it since the goal is an analysis against the presented rules of the OP's imaginary world. In short, that tag has absolutely nothing at all to do with science, no matter what the post reads like.

ONE MORE WORD!

I am absolutely against updating meta post titles with things like the date of the post (as you did with the aforementioned internal-consistency discussion). That's far more likely to cause people to believe that, due to age, the policy doesn't apply when that is entirely false.

Please stop what you're doing and let's have a community discussion about your project and its goals. That has started from a certain point of view here. As a basic rule-of-thumb, don't modify other people's posts without either their individual permission or the consensus of the community.