We all know that some objects (a feather, for example) fall much slower. The metal weights were dense enough that gravity overwhelmed air resistance. Galileo was performing an experiment about gravity. Air resistance was merely a small complication which could be ignored. In the absence of air (in a vacuum), the feather falls at the same speed as a ten-pound weight. Astronauts on the moon performed this experiment, and the feather fell at the same rate as a metal weight. Actually, that experiment has been performed thousands of times, by students, in partial vacuums here on earth. ; Proof of my Latest Experiments