I was reading something which is supposed to mean "Why is it moving?". I would translate it as なんで動いているか？ but it actually says なんで動いてんだ？
What's the difference between them? I think I cannot capture that nuance.
I think that 動いている it's something that it's moving at this time whereas 動いてんだ sounds more like I'm stating that it's moving, but I find the lack of tense disturbing (maybe it's a very strong statement implying surprise).
Another question: Could I even say なんで動いてんだった？ meaning "why was it moving?" instead of なんで動いていたか？