Aristotle stated that heavier objects fell faster than lighter ones. Galileo stated the following thought experiment:
Imagine two unequal balls dropped from a height at the same time; according to Aristotle, the heavier ball would drop faster. Now imagine the same experiment with one difference: the two unequal balls are joined by a cable between them. If it was true that the heavy ball moves faster and the light one moves slower, then the light ball will hold back the heavy one. If Aristotle was correct the two balls tied together would not reach the ground as quickly as the heavy ball alone. But if we assume that the cable between the balls has the effect of turning the two balls into a single mass that is heavier than either one by itself, the joined balls should drop faster than either one by itself.
Another way of looking at this is the reverse:
A heavy object is dropped from a height. As it descends it cracks and splits into two objects, each of which is lighter than the original object. Will the two objects suddendly slow to half speed?
One can continue the above thought experiment and question what would occur if each of the two objects divided into two …. If the speed did in fact halve then one could imagine subdividing further to a point at which it appeared that the objects would fall very very slowly.