The tag is very vague on when it should be used.

Yes, there's a wiki on the main site here that says how to use it on this site, but what 'markers,' if you will, suggest whether a question should go on one of the Science SE sites or on the Worldbuilding site? Assuming the question is on topic for one of the Science SE sites, should it go there, where there will likely be more people that know about it, or on the Worldbuilding SE? Would the question have to be checked on a case-to-case basis?


3 Answers 3


It helps to understand how the three tags work

The , and tags are mutually exclusive, meaning you can only use one. Unlike nearly all other tags, they do not scope or categorize the question, they limit or scope the answers.

  • means to use known science as a frame work to create an imaginative solution that may — or may not — eventually prove true. For example, in your world you might want a space capsule that embraces a Dr. Who TARDIS-like interior. A answer would be to associate the scientific concept of a pocket universe to rationalize the idea in your world. Is it "science?" Not really, because pocket universes are only mathematically theorized where science requires empirical evidence and repeatable tests.

And that is a HUGELY IMPORTANT distinction. Too many people think that mathematical theories are science. They're not. The word "science" is defined as, "the systematic study of the structure and behavior of the physical and natural world through observation, experimentation, and the testing of theories against the evidence obtained."

  • means the answer must reflect known science with little imaginative extrapolation. Thus, the previous example of a TARDIS-like environment can't actually be answered if the tag is involved (we'll try, though... we're only human, after all). On the other hand, "what are the significant weaknesses of a spider mech?" could be because the mechanical limitations of articulated legs are known and can be referenced.

  • is equal to with one additional requirement: prove it! Thus, the previous example of a spider mech could be answered with the tag because mathematics and academic articles about articulation can be cited as proof of the answer.


  1. We do expect questions to have a worldbuilding context. While it's never been definitively established, the more you're just looking for a real-world explanation the more you'll see down votes. You need to explain what's different with your world. For example, we have no problems answering a question about orbital insertion when you describe your fictional space ship. In fact, the hard-core astrophysicists on this site tend to have a lot of fun with questions like that.

  2. It should be noted that Stack Exchange isn't designed to replace an education. That sounds rude on the surface, but it makes sense when you think about it. You need to ask yourself whether or not you can actually use what you're going to get or, worse, whether or not you can even judge the quality of two answers to determine which is the best. Too often users who lack a full college education in a hard science will use the tag believing that what it will guarantee is a better answer. Nothing could be further from the truth. All it guarantees is that the answers you get are less speculative than might be seen with the and tags. And that makes a lot of sense when you remember that our stated goal in the Help Center is to help you build imaginary worlds. In other words, speculation is literally what we're here for.

When should you pitch another Stack?

If you're asking for the gory details in a real-world context, the question doesn't belong here. That's not 100% entirely true (there's a lot of history I'm not bothering to link...), but it's a safe way to ensure nobody will complain.


The way I understand it, a question about a problem in speculative fiction requesting a hard science answer is still a question about a problem in speculative fiction. It does not ask for a scientifically correct answer. What it asks for is a sciency answer.

The difference between a scientific answer and a sciency answer is like the difference between a true piece of news and a truthy piece of news, or between truthfulness and verisimilitude; that is to say, the sciency answer should look like science and sound like science, it should be backed by quotations and equations and diagrams and so on, but it definitely does not have to be scientifically or technologically correct — exactly because the fundamental context is speculative fiction and not real science.

The quotations backing up the answer might have been cherry picked, or might have been placed in an unexpected context. The equations might have been used outside their domain of applicability. The diagrams might have been drawn tendentiously. The answer might have been based on wild guesses, on as yet untested hypotheses, or even on hypotheses known to be false...

Long story short, WorldBuilding SE is not the correct place to learn physics, or chemistry, or geology, or history, or linguistics or whatever actual science. On WorldBuilding we assume that everybody already knows the real world science, either from their general culture or from the diligent research they have done before asking a question, and the answers to be provided are intended to help with the creation of a fictional world.


I think the line should be drawn at the importance of the worldbuilding aspect in the question.

To take a recent question as example, an orbital transfer to the anti Earth can make sense for worldbuilding, less for space exploration, because in a strictly real world sense such configuration would not be stable long enough to allow space travel development.


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