Galileo's experiment

We found this jigsaw on our cruise ship. So the story goes, Galileo used the tower to drop objects of different mass. Previously Aristotle had suggested that the heavier an object was, the faster it would fall. Hence if a heavy and a light object were dropped at the same time, the heavy one would hit the ground first. I love to show classes that a metal weight and a screwed up piece of paper hit the ground at the same time, It just seems so counter-intuitive. However, here is a bit of reasoning: Take two identical metal weights and hold them side by side. Drop them. Logic says they will hit the ground at the same time. Now glue them together. What has changed? Why would they fall twice as fast just because they have been glued together? Try this for more info https://en.wikipedia.org/wiki/Galileo%27s_Leaning_Tower_of_Pisa_experiment