Once your heads stop hurting...take that example (sample rate=96k, wheel spinning at 48k) and contemplate what you would see if the wheel sped up to 49 kHz.
It would appear to move slowly, an illusion known as aliasing! On playback we would be creating something that wasn't there - a by product of our sampling rate. This is the reason for 'brickwall' filters that don't let any frequencies beyond 1/2 the sampling rate into the ADC - to avoid aliasing.