Galileo dropped spheres of different masses from the Leaning Tower and measured their fall time. At the same time, he dropped two balls from the tower: a heavy cannonball with a mass of 8 kg and a lighter musket ball with a mass of 20 g. Both bodies (they had a similar shape) reached the ground at the same moment. He proved that the time of their fall was the same. This proof is one of the foundations of classical mechanics.
However, this event is questioned by some scholars and historians, although no one doubts that Galileo used balls rolling down an incline to study their speed and acceleration.
