5) I turn the whole; the part turns.
9) I turn the part; the whole turns not.
0) Five turning circles has the part; four the whole.
What is the whole? What is the part?
As always, a good answer will not only give the correct answer to the riddle, but will also explain all of the clues.
Look at the tags.
The answer for the whole is an extremely specific thing (and yes, it is physical).
What is the significance of the contant repetition of 'turn'?
Even the Romans would do better than you're doing!
What if you replace 'turn' with the synonym 'roll'?
I will add more hints if people are having difficulty.