A lot of conceptual questions in physics cannot be asked in few sentences. Because the idea or image of the subject in questioner's mind which is the actual root of the problem is never projected in few lines. So is a discussion possible on this site? where one can better understand other's problems. Otherwise the questioner remains unsatisfied.
The site isn't intended for discussions. In fact avoiding long rambling discussions is a key aim of the Stack Exchange group.
If you can't focus your problem into a reasonably concise question then you need to go off and research the area. The internet is such a rich resource that there's really no excuse for not doing your own leg work.
That doesn't mean you can't ask conceptual questions, but they have to be well specified ones and the anticipated answer has to be reasonably concise as well. If the answer to your question would effectively be a blog post then you should search the web for a blog post instead.
Having said all this, you can always ask your question anyway and see if anyone answers it. The worst that will happen is that it gets downvoted and closed, and you can always delete it to remove the stain!
There's a difference between discussion and asking a question in a few lines. You can certainly ask questions that are longer than that; in fact, the ideal question length is probably 15-30 lines, and there are plenty of examples of well-written questions that are longer than that. The key is that it should be answerable: your question should be able to be addressed by a single post from someone else (which can also be long). It should not require a back-and-forth discussion.
Sure, sometimes you need to ask for clarification on an answer (or others need to ask for clarification on your question), which is why we have comments, but the content of the comments is supposed to be incorporated into the post. At the end, we should wind up with one question and some number of answers that directly address the question, and that's all.