If no air resistance is present, the rate of descent depends only on how far the object has fallen, no matter how heavy the object is. This means that two objects will reach the ground at the same time if they are dropped at the same time from the same height. This statement is proven by the law of conservation of energy. If gravity is a constant on all objects then what would be the different force acting on the heavier object? In school we demonstrated this by a penny and a feather in an airless glass tube. The feather and the penny hit the bottom at the same time because there was no air resistance.
If air resistance plays a role like it does in the real world then the shape of the object is central. If a penny and a feather are dropped from the empire state building, the penny will of course fall faster. The feather has a flat shape and air is easily trapped underneath it so it will be slowed. If you are dropping a 14lb bowling ball and 30lb bowling ball the difference in when they both hit the ground will be unseen. They are both the same shape so the same air resistance.
Galileo did experiments to try to find a formula for falling objects about 400 years ago. He started the experiments at the age of 31 and was finished when he was 42. When he presented the idea many thought he was wrong because he couldn't prove them. With no vacuum air resistance always played a role. He was forced to say his ideas were wrong and forced to stay in his villa by the Spanish Inquisition.
Probably his most famous experiment dealt with this topic. This experiment was proving wrong an earlier theory made by Aristotle that a heavier object would fall faster than a light one. At this time most people accepted this theory and