SI Units form the official language of international science. As such I want to discuss whether questions that are tagged for either or should automatically warrant the use of only metric SI Units.

I ask in relation to several answers to Quick solutions to a modern warning placed on the surface of the earth for future generations, where initially only imperial measures were used without even offering conversions.

This question is not intended to be a debate about the differences between units of measure currently in use in the USA in comparison to the traditional British Imperial System. In New Zealand we officially only use metric, but we have a lot of first generation ex-pat Brits who casually use Imperial Units interchangeably with their metric near equivalents - yards for metres, miles for kilometres (which is problematic because they're really not the same thing), etc... and we have a lot of media made for the US market in which Customary Units are used, which apparently differ, but they just get read the same way.

Nor is this about the use of Imperial or Customary Units in general like Imperial vs. Metric System.

This is purely about whether we should expect questions and answers tagged or to only use the internationally recognised scientific units of the SI system.

Note well: We are not debating the relative merits of a given system of measurements only whether science questions should automatically require a particular system.

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    $\begingroup$ I'd just like to note that SI units aren't always used in science. For instance, cgs units are widely used in astronomy. Mean planetary densities, often given in grams per cubic centimeter, are an example you might have seen around here. Oh, and then there are the really weird ones that don't make up any particular unit system - parsecs, solar luminosities, etc. $\endgroup$
    – HDE 226868 Mod
    Commented Aug 13, 2018 at 17:44
  • $\begingroup$ Its not required, but it is standard for a good science-based answer to use metric here. I write this as one of this site's premier spherical-cow physicists and American-unit-user. I enforce the standard with snarky comments. $\endgroup$
    – kingledion
    Commented Aug 15, 2018 at 5:08

1 Answer 1


No, tags should not add more implicit requirements to questions/answers

We already have problems with explaining to people that is different from every other tag that exists on the main site because suddenly answers are required to cite their sources and provide calculations and such, while the question has to suddenly adhere to the same scrutiny. I don't think it's a good idea to add more implicit rules to this. Especially not by widening it to other tags. Suddenly has lots of extra requirements about the quality and has a few. The next thing will be that should have less, apart from a codified version of "What's your magic system?" and needs to have certain keywords like "check", "my" and "numbers" in it. Tags are intended to categorize questions so that it's easier to find them. They are not supposed to add restrictions to the answers. What is acceptable as an answer is defined in the question.

Every question should be clear about what is acceptable and what is not acceptable. It's custom to use the same units as the querent, but if a querent absolutely does not want imperial units in answers to his science-based question they should explicitly mention it. Just state that you need SI units and that answers should provide them. If they don't they are not an answer - though it's likely not that hard to convert the numbers yourself, so flagging them doesn't seem to be relevant in the generic case.

If someone uses units that weren't present in the question we can point them to Systems of measurement and ask for units that correspond to those used in the question. Or just edit them in. For most units it should be easy enough to ask Google for a calculation about the important input numbers and the results. We don't necessarily need to convert every single step.

If you want your science-based question in imperial units then you can have it in imperial units.

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    $\begingroup$ Adding to this, measurements can always be converted from one system to another. It's not like that substantially changes the content of the question or answer. $\endgroup$
    – user
    Commented Aug 13, 2018 at 13:01
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    $\begingroup$ To add to this: special rules, whether Worldbuilding's (like hard-science) or SE's (like what comments are for, or polling questions) are especially opaque to new users, who don't know where to look or that they should look for them. That doesn't mean never have rules (that way lies chaos), but we should consider the cost of any new rule. $\endgroup$ Commented Aug 13, 2018 at 13:03
  • $\begingroup$ @MichaelKjörling Although I have had edits rejected as too radical for adding unit conversions on other stacks. $\endgroup$
    – Ash
    Commented Aug 13, 2018 at 13:03

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