I recently discovered that we have a real-world tag.
Firstly, I'm really not sure when this tag is meant to be used. It can't be for all out-of-universe questions, as it would then have a lot more than 35 questions to its name. The tag wiki doesn't give much help or clear guidance:
This tag usually refers to how something in Sci-Fi or Fantasy works in the real world. It can also refer to a version of our world featured in a Sci-Fi or Fantasy work. For instance, Stephen King uses a version of himself in what is supposedly our world in his Dark Tower novels.
Secondly, we have a policy (and even a custom close-vote reason) that questions asking about real-world science are off-topic unless somehow linked to a particular work of SF/F. This policy is still unclear, however, and having a tag that seems to apply to such questions is only going to exacerbate the problem.