Just a few things we owe Galileo in physics:
* The principle of relativity. You might think that was Einstein, but the first theory of relativity was by Galileo in his 1632 "Dialogue Concerning the Two Chief World Systems" (before Newton was even born!). Galileo introduced this idea with a brilliant thought experiment: He asked the reader to imagine being in a windowless cabin on a smoothly sailing ship. He argued that no experiment you could perform inside the cabin (dropping a ball, watching flies, etc.) could tell you whether the ship was at rest or moving at a constant velocity. All the laws of mechanics would behave identically. This is the cornerstone of classical mechanics. In the context of special relativity, Einstein "merely" added 'the speed of light is c' to the list of laws of nature that hold in all inertial frames. But the general way of viewing laws of nature relative as being invariant to motion was Galileo's (the principle of inertia), and essentially the starting point for Newtonian mechanics. It doesn't seem like the work of someone only able to fiddle around with scales.
* The Law of Falling Bodies: The discovery that the distance an object falls is proportional to the square of the time. The first truly modern mathematical law of physics.
* Detailed telescopic observations: Moons of Jupiter, Phases of Venus, Mountains on the Moon & Sunspots, etc.
When reading about ancient Greek mathematics it always is striking how little it resembles the mathematics taught in schools and how much it resembles the mathematics taught in University.
Pre-university schools, even today, focus on teaching practical math. Most people can get by just fine without skills in abstract math, theorizing, and proofs (though those skill would make a lot of people much better at whatever they do).
It's obvious that "practical math" has always been the most important and first skill to teach. But that ends at basic trigonometry.
Students are learning how to do integration in highschool (not exactly a relevant skill), long before they are confronted with the idea of proof in mathematics.
I then found that what I was going to argue was his big achievement was not as original as I had thought: https://en.wikipedia.org/wiki/Galileo's_Leaning_Tower_of_Pis...
On the other hand he still seems to have made a significant contribution to laws of motion in his writing, but I am not sure.
It still took like a thousand years for this to be experimentally demonstrated.
The important part of this "thought experiment" in the history of science is that it is part of the shift to empiricism that really drove science. It was important to go from "Well they were smart and they said, so it must be true" to "I don't care how smart you are, what you say doesn't match the data"
This is important, because "smart" people like Archimedes said a lot of stuff that was never true, but was taken as true for a millennia, often because it "sounded" right or obvious. More importantly, Archimedes could have done the exact same experiments that Galileo (and others) used to demonstrate he was not correct. There was no technological advancement required. He didn't, because the philosophy at the time was to "just think really hard about it" and "reason from first principles" and you would obviously get the right answer if only you are smart enough. Who needs data? You're smart and you thought hard about it, so you cannot be wrong!
People should recognize how important that is to remember in the current world.
He still made a major contribution, but if other people had done the "drop balls of the tower" experiment before his time, then the move to empiricism was underway and that does make his contribution a lot less.
To be fair, I think we often think of things being achieved by a big breakthrough by an individual when the reality was that the big breakthroughs are the result of lots of small changes - Newton's "shoulders of giants".
Interesting, looking up that phrase, I find that was not original either, but goes back to at least the 12th century.
Galileo's argument is that the theory where heavier objects fall faster is inconsistent a priori, because affixing a small stone to a larger stone would cause the composed object to fall faster than the smaller stone was falling when it was free. However, there is no logical contradiction here: what could happen is that the combined object would have an acceleration that is the (weighted) average of the acceleration of the components - slower than the lighter object but faster then the heavier object.
In fact, this is exactly what happens in an electric field: if you have two objects with the same mass but different negative charge moving towards a large positive charge, they will accelerate at different rates (the one with the bigger negative charge will "fall" faster). If you then tie the two objects together, you'll get a combined object that has more mass and more charge; the total electric force will increase, but its larger total mass will mean that it accelerates less. Alternatively, you can explain it as the less charged object dragging the heavier object down, such that the combined object moves at an average of their speeds.
The fact that this doesn't happen with gravity is a very special property of gravity, that only experiments can prove. A priori, gravitational mass/charge could have been entirely unrelated to intertial mass, just like electrical charge. Only much later, with Einstein's general relativity, did we get an explanation of gravity that makes this more than a coincidence - and it turns out that gravity is not a force at all, at least not one that acts on objects.
https://chatgpt.com/share/68dd758f-2bc0-8008-955d-a7dbd89399...
" Given:
- The blog offers no primary evidence for Descartes’s having a proof.
- Scholarly histories, based on critical assessment of surviving letters, treat the solution of the area problem as due to Roberval (and independently Torricelli) rather than to Descartes.
- The more carefully vetted sources place Descartes in the position of reacting to, or endorsing, Roberval’s result but not of originating it.
Therefore, the weight of evidence supports that the historical consensus is correct — Descartes did not solve the area under a cycloid; the blog's claim is likely an overstatement or misinterpretation."
