Galileo claimed that if there was no air, a cannonball and a feather would, if dropped, hit the ground at the same time. One of the Apollo astronauts did this experiment on the moon with a hammer and a feather.
At the NASA’s Space Power Facility in Ohio, there is a huge chamber which can pump out all the 800K cubic feet of air, some 40 tons, leaving only a few grams. It is a near perfect vacuum. They conduct the experiment and show video in slow motion.
An interesting point is made: We watch this and say that the feather and ball are falling. But wee see this occur in relation to the backdrop. Einstein would say that they not falling.