Galileo's Leaning Tower of Pisa Experiment

Galileo and the Leaning Tower of Pisa have taught us a lot about free-falling objects. Yes, the same tower which could not stand up straight due to its weight, ended up playing an important role in discovering one of the fundamentals of physics. Galileo had the vision to go against Aristotle's ideas, and the experiment that he performed proved him right. So, what was this experiment? Keep reading to find out.

Galileo's Leaning Tower of Pisa Experiment Explained

It was the Italian scientist Galileo Galilei who performed the famous experiment that proved that the acceleration at which objects fall is the same irrespective of their mass. That experiment is known as Galileo's Leaning Tower of Pisa Experiment. Its result was a direct violation of Aristotle's theory of gravity which assumed that objects fell at a rate that is directly proportional to their mass.

Archimedes' prediction of the experiment (left) and Galileo's measurement (right), Wikimedia Commons CC-BY-SA-3.0.

Although it's still not clear if this famous experiment was conducted in reality or if it was a thought experiment, Galileo Galilei is said to have conducted it around 1589. He dropped two spheres of different masses from the top of the Leaning Tower of Pisa because he wanted to demonstrate that the objects would fall at the same rate independent of their masses. Indeed, the two spheres hit the ground at the same time, supporting the idea that objects fall at the same rate regardless of their masses. This was again proven to be true years later when the Apollo 15 astronaut David Scott dropped a hammer and a feather from the same height on the Moon and they hit the Moon's surface simultaneously. Before Galileo's experiment, Aristotle's theory of gravity was widely believed, which stated that objects fall at a rate that is proportional to their masses. Quite a while after Galileo's experiment, he provided a theoretical explanation for this phenomenon.

Galileo's ball drop thought experiment

Galileo's ball drop thought experiment was crucial in understanding the effect of acceleration due to gravity on a falling object, and it ended the debate once and for all. It proved that Aristotle's theory of gravity was incorrect. Let's look at what Galileo thought about!

Imagine standing on top of the Leaning Tower of Pisa. Assume heavier bodies fall at a higher rate than lighter bodies. You now drop two balls of different masses from the top but there's a catch: the balls are connected by a string. According to the assumption, the heavier ball would fall faster than the lighter ball, so the string would be pulled taut: the tension of the string is pulling on the heavier ball which should therefore reduce its acceleration.

All objects fall at the same rate, StudySmarter Originals.

But this would mean that if we drop the heavy ball without any attachment, its acceleration would be greater than the system where two balls are attached. This contradicts our initial assumption where we say that the heavier body will fall faster: the whole system should fall faster than any individual ball. Thus, our assumption is false: the only possible explanation is that all bodies will fall at the same rate regardless of their masses.

Galileo's theory of gravity

Galileo determined through his experiment that the items fell with the same acceleration, verifying his prediction and disproving Aristotle's theory of gravity, which states that objects fall at a speed proportional to their mass.

Galileo and acceleration

Aristotle had claimed that force causes speed, but this was again disproved by Galileo who claimed that force causes acceleration. This was again derived from his falling bodies experiment. He predicted that the speed of bodies falling toward the earth is constantly increasing. This increase in velocity, also known as acceleration, is caused due to the force of gravity. We can prove this with an experiment.