Can a question be closed or called a duplicate if it has already been asked with or without answers on another Stack Exchange site?
Since many topics of physics and biology tend to intersect with chemistry, is it possible that a question might be called a duplicate for being asked on another site?
Can a person post the same question on two sites to get the answer from different perspectives or in case it is unanswered in one site?
This is called "cross-posting," and has been discussed on Meta previously.
The general guidance is to be upfront about what you are doing. It's generally poor form to post exactly the same question on multiple sites, because each community has different expectations about their questions and offers different expertise. If you post closely-related questions on different sites, it is polite to link each question to the other. As a rule, if other users discover your cross-posted questions, they'll add such a link in the comments, but it's better for you to do so yourself soon that you can provide some context about you expect from each community.
We occasionally have users who cross-post all of their questions. Don't do that, please. We expect contributions to Physics to be substantially original.
