The earth's rotation acts as a clock and defines a rather precise unit of time called the day. We could go out in outer space and spin a marble and get a reasonable clock. On the other hand, it is my understanding that you can't do this with an electron, that is, you can't start an electron spinning and then tell time by looking at the electron. Is this correct? Assuming it is, what is the smallest object you can use as your “spinning marble”? Would an atom of tri-substituted methane, ie CHFClBr or flouro chloro bromo methane work? What about a proton with its 3 quarks? In short, what object qualifies as the smallest possible spinning clock?