If I attach a weight to a string, and spin it, I notice that the faster I spin it, the more it pulls away from me. So, I imagine what would happen if I arranged a very large machine, designed so that it would spin a big weight in a circle, accelerating it so that it moves fast when the weight is pointing north, and slow when it is pointing south. Since the weight is pulling on the center more strongly when it points north, doesn't that mean that the machine as a whole should move in that direction?
This sounds like it would produce movement without the need for any thrust, i.e. the machine would go forward, but nothing would be sent backwards in reaction.
Since I'm pretty sure I'd have heard of it if newton's third law was somehow disproved, I imagine I'm missing something - would this machine not work? If it does work, where is the equal and opposite force?