When we hear of a “thought experiment” today, we usually think of Albert Einstein. But there is an unsung hero of this skill that is rarely talked about, Galileo Galilei.
Now, you may be thinking that I am talking of the Leaning Tower of Pisa, Galileo’s most famous experiment. But no, this is purely a thought experiment, it doesn’t involve climbing 294 steps up a leaning tower in Italy.
Background of Galileo’s thought experiment
Galileo developed his thought experiment to challenge the Aristotelian view of free-falling bodies which was widely accepted at the time.
According to the Aristotelian approach, heavy objects fall faster than lighter objects.
Galileo knew this wasn’t right but it was difficult for him to disprove such a powerful assertion. Everyday experience seems to indicate that heavy objects fall faster than lighter objects.
So Galileo devised a clever thought experiment to challenge the long-standing view of falling bodies.
Galileo’s thought experiment on falling bodies
Galileo’s thought experiment seeks to disprove the Aristotelian view by way of contradiction.
Suppose you have a heavy object and a lighter object and tie them together so that they now fall as a unit.
The heavier object will fall faster than the lighter object. So, it’ll pull down on the lighter object through the cord. Meanwhile, the lighter object will fall slower, so it will tend to pull up on the heavier object. The overall effect is that the system will fall slower than the heavier object and faster than the lighter object.
However, according to the Aristotelian view, that system should actually fall faster than the heavier object because it’s bigger total weight.
Galileo’s Leaning Tower of Pisa Experiment
Today, we know that heavier and lighter objects all fall at the same rate, which is where Galileo was going with his thought experiment.
Clearly, Galileo knew it was going to take a lot more than a thought experiment to convince people. So he took a bold move to prove his point. He designed an actual experiment at one of the biggest stages in Europe at the time.
Apparently, Galileo dropped two spheres of different weights from the Leaning Tower of Pisa and an audience at the bottom verified that they both hit the ground at the same time.
This would go down as one of the seminal experiments in physics – maybe a little pun intended.
Modern Experiments
Whilst there is a divided opinion on whether Galileo performed the Leaning Tower of Pisa experiment.
Today, we know that Commander David Scott, an astronaut of the Apollo 15 dropped a hammer and a feather on the Moon. They landed at the exact same time.
Even more impressive, English physicist, Brian Cox, did a similar experiment at NASA’s Space Power Facility in Ohio, United States. The experiment, documented by BBC’s Human Universe, involved a bowling ball, a feather, and the world’s biggest vacuum chamber.
Unfortunately, Galileo didn’t have the technology to take him to the Moon nor the facilities of a large vacuum chamber to prove his ideas. But I’m sure he would’ve been pleased with the subsequent modern efforts to verify his ideas.
I wonder what Aristotle would have to say about say about that?
