I just took at look at the question linked in this post, version 4.
I think the question was closed because it's vague and too broad, not really because it's about biology.
I think this happens a lot on our site and warrants discussion.
Consider the first three paragraphs of the post:
Let's, for example, take a ribosome. It is an enzyme that is in turn just a molecule that must follow the laws of physics.
Correct me if I'm wrong, but it can be looked upon as a molecular machine made up of several pieces. What exactly makes those pieces work together?
Why does the ribosome bind to a strand of RNA? Is it just the shape and electric charge or is it something more? Once the ribosome is bound to a piece of RNA, how does it move?
There are four question marks by the end of the third paragraph:
- "What exactly makes those pieces work together?"
- "Why does the ribosome bind to a strand of RNA?"
- "Is it just the shape and electric charge or is it something more?"
- "Once the ribosome is bound to a piece of RNA, how does it move?"
Having multiple questions is alone a problem.
When faced with multiple questions, a would-be answer writer has to read, understand, think about, formulate answers for, and then write answers for multiple questions.
If the probability that a given reader can do those things for one question is p << 1, then the probability that a given reader can do them for four questions is p^4, which is absolutely tiny.
This puts a reader at a disposition to regard the question as unanswerable.
Now, a deeper problem is that the questions bounce back and forth from specific and physics-oriented to broad and biology oriented.
Questions #1 and #2 are very broad and sound biology-ish.
A typical physicist probably feels that only a phenomenological bio or so-broad-as-to-be-useless physics answer can possibly suffice.
This, puts the physicist at a mind to vote for closure.
Then in question #3 we get physics: "Is it just the shape and electric charge or is it something more?". That is a physics question.
Or at least it suggests one.
We could rewrite the entire post around that one question:
Ribosomes perform complex tasks in the organism, but in the end they are just molecules and therefore governed by the laws of physics.
What physical principles are the most crucial for understanding how a ribosome is able to function as it does?
To choose a specific example, is electrostatics enough to explain why a ribosome sticks to a strand of RNA?
Unfortunately, we then get question #4: "Once the ribosome is bound to a piece of RNA, how does it move?"
This is again vague and broad.
Does the asker want an explanation from the bio point of view or a purely electrodynamical description?
Why (I think) the post was closed
Vague, broad posts like this invite closure because they're hard to answer.
As they translate to "how does X work?", they invite too many possible levels of scope.
Posts like this could reasonable be closed as "too broad" or "unclear what you're asking".
However, I think its psychologically easier for readers to perceive a question as possibly ok for another audience rather than stick their chin out and tell the OP that their question is bad.
Hence, we see a lot of questions closed as "off topic" where "too broad" and "unclear what you're asking" would make more sense.
At least, that's my guess.
This is not a great situation because "off topic" tells OP to go somewhere else, rather than learn how to ask questions better.
We definitely want better questions more than we want to turn people away, so...
What do to
Use "off topic" only as a last resort.
Prioritize close reasons which help OP learn to ask better.
If you can, edit the post to zero in on the relevant question.
The example I pose above is probably too big of an edit, but a comment can help OP get there.
It may also be ok to make a substantial organizational edit and post a comment reminding OP that they can roll it back if it misses the mark.
So what about the place of biophysics?
I think interdisciplinary questions get closed a lot because, as illustrated above, it's easy to lose focus and put readers in a state of mind where they feel like the question gets so large that a good physics answer can't address it.
I think biophysics questions in the vein of my example rewrite given above are solidly on topic.
So, with all this said, I really think the only legit answer here is that we need to see more good biophysics questions before we can even consider writing down explicit descriptions of which ones are and are not on topic.