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   John Carlos Baez (johncarlosbaez@mathstodon.xyz)'s status on Monday, 02-Dec-2024 02:31:16 JST John Carlos Baez

   If fundamental physics were making big progress, I'd be all over it - that's what I wanted to do ever since I was a kid. But it's stagnant: the action is elsewhere, like using category theory to design radical new kinds of software. So these days I get some of my physics fix by studying the *history* of physics.

   After studying the hell out of particle physics and general relativity, I went back and dug into the history of electromagnetism, which is really just as fascinating. Now I'm going back to medieval physics - because the idea that everyone was an idiot until Galileo is just plain wrong.

   "Natural philosophers" in the 1200s and 1300s developed key concepts, utterly necessary for modern physics, but almost invisible now because we're so used to them - except for students, who find physics really hard because we don't bother to CLEARLY EXPLAIN those concepts: we act like children are born knowing them.

   I'm talking about concepts like "the speed of an object at a moment of time". What the hell does that even mean? How can you figure out how fast something is going in one instant of time, when doesn't have time to go anywhere?

   Well, that was clarified by calculus, and we credit it to Newton and Leibniz. But they had to have the idea already, in order to clarify it! And the idea of "instantaneous velocity" was developed around 1340 by the Oxford Calculators, a school of thinkers like Heytesbury and Swineshead - geniuses we never hear about.

   Now I'm going back further. Did you know that back in 420 AD Martianus Capella had a theory where Mercury and Venus revolved around the Sun? And this was known to thinkers in Charlemagne's day... and also Copernicus! Wow!

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     simsa03 (simsa03@gnusocial.jp)'s status on Monday, 02-Dec-2024 02:55:48 JST simsa03

     in reply to
     As an addition: Although the "idea of 'instantaneous velocity'" was develped by the Oxford Calculators, it was the School of Orseme (Nicole Oresme, Paris, 14th century) that gave a mathematical (i.e., graphical) proof for the "Merton Mean Speed Theorem". It was less the Oxford Calculators but the School of Orseme that rendered the Aristotelian concept of motion (impetus theory) obsolete. The main reason for the development of a new theory of motion of flying heavy objects was that the Aristotelian impetus theory was unsuited to adequately calculate trajectories of projectiles in military combat, esp. against fortresses.
     John Carlos Baez and DougMerritt (log😅 = 💧log😄) like this.
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     John Carlos Baez (johncarlosbaez@mathstodon.xyz)'s status on Monday, 02-Dec-2024 02:59:51 JST John Carlos Baez

     in reply to

     • simsa03

     @simsa03 - I love Oresme! Heytesbury gave a *verbal* proof of the Mean Speed Theorem, which I could never understand until someone explained it to me yesterday:

     https://johncarlosbaez.wordpress.com/2024/11/07/the-mean-speed-theorem/#comment-186034

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     Markus Redeker (mrdk@mathstodon.xyz)'s status on Monday, 02-Dec-2024 04:57:52 JST Markus Redeker

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     • simsa03

     @johncarlosbaez @simsa03 Yes, #Oresme was quite interesting. I know him for two other achievements:

     1. Relativity of motion: He had already the famous “ship argument” that #Galileo used to show that physics in a moving object must be the same as in a standing one — the only difference is that Oresme, living in Paris, used a ship on a river and not on the sea. (https://todayinsci.com/O/Oresme_Nicole/OresmeNicole-Forerunner.htm)

     2. He proved the divergence of the harmonic series. (https://en.wikipedia.org/wiki/Nicole_Oresme#Mathematics)

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     Σ(i³) = (Σi)² (svengeier@mathstodon.xyz)'s status on Monday, 02-Dec-2024 06:10:54 JST Σ(i³) = (Σi)²

     in reply to

     • simsa03

     @simsa03 @johncarlosbaez
     The earliest notion of a "instantaneous motion" known to me would be in Bhāskara the 2ⁿᵈs works on planetary motion, around ~1200 https://en.wikipedia.org/wiki/Bh%C4%81skara_II#Calculus