# Physics Before Galileo in the 15th Century

Leonard Kelley holds a bachelor's in physics with a minor in mathematics. He loves the academic world and strives to constantly explore it.

We can clearly see that the eventual arrival of classical mechanics and much of the background for other branches of science was taking root as we get closer to Galileo's time, and it was during the 15th century that many of those plants began to sprout out of the ground. The Mertonians and Bradwardine’s work was especially critical, but none of them ever developed the idea of energy. During this timeframe, the concept began to sneak in (Wallace 52).

Motion was being thought of as a ratio that had existence outside of a particular circumstance, as the Aristotelians contended was the case. To the Mertonians, motion wasn’t even a point of reality but rather an objectification of it and they didn’t bother with the distinction between violent (man-made) and natural motion, as the Aristotelians did. However, they did not consider the aspect of energy in any situation. This changed with Albert and Marsilius of Inghen. They were the first to split the broad concept of motion into dynamics and kinematics as they sought to provide a real-world explanation, and this was a step in the right direction (Wallace 53-5, Hoenen).

With this in mind, Gaelano de Theine picked up the baton and continued on. His goal was to make bare the distinction between uniform and non-uniformed motion as well as methods for measuring uniform motion, hinting at kinematics. To demonstrate this as a real-world application, he looked at spinning wheels. But once again, energy did not enter the picture as de Theine was focused on the magnitude of motion instead. However, he did create a new notation system which was also messy like the Mertonians':

• -U(x)~U(t) (constant velocity over a distance x and not over a time interval t)
• -U(t)~U(x) (constant velocity over a time interval t and not over a distance x)
• -U(x) · U(t) (constant velocity over a time interval t and over a distance x)
• -D(x)~D(t) (changing velocity over a distance x and not over a time interval t)
• -D(t)~D(x) (changing velocity over a time interval t and not over a distance x)
• -D(x) · D(t) (changing velocity over a distance x and over a time interval t)

Alvano Thomas would also create a similar notation. Note how this system doesn’t address all the possibilities that the Mertonians' did, and that U(t)~U(x) = D(x)~D(t), etc. displays quite a bit of redundancy (Wallace 55-6, 96).

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Many different authors continued this study of the distinctions of different motions. Gregory of Rimini contended that any motion can be expressed in terms of the distance covered, while William of Packham held that old viewpoint of motion being inherent to the object itself. Where he differed was his critique of the notion that motion was something that could exist one moment and not exist the next. If something exists, it has a measurable quality to it, but if at any point it doesn’t exist then you cannot measure it. I know, it sounds silly, but to the scholars of the 16th century this was a huge philosophical debate. To resolve this existing issue, William contends that motion is just a state-to-state transference where nothing is truly at rest. This in of itself is a big leap forward. He goes on to state the causality principle, or that “whatever is moved is moved by another,” which sounds very similar to Newton’s Third Law (66).

Paul of Venice did not like that and used a continuity paradox to illustrate his displeasure. Otherwise known as Zeno’s paradox, he argued that if such a state-to-state transference were true, then one object would never be in a single state and thus would never move. Instead, Paul claimed that motion had to be continuous and ongoing within the object. And since local motion is a real phenomenon, some cause had to exist, so why not the object itself (66-7).

And of course, it would be remiss of me not to mention Leonardo da Vinci, the master Renaissance man. While his work bordered two centuries, his starting point was at the end of the 15th century. He deserves an article all unto himself, so this is just a brief aside. Through his artwork, we have seen his plans for flying machines and optical studies, amongst many other things. Had he shared some of his studies rather than keep them for himself, who knows where science would be now? (Amsen)

## Works Cited

Amsen, Eva. "Leonardo Da Vinci's Scientific Studies, 500 Years Later." Forbes.com. Forbes, 02 May. 2019. Web. 03 May 2021.

Hoenen M.J. (2011) Marsilius of Inghen. In: Lagerlund H. (eds) Encyclopedia of Medieval Philosophy. Springer, Dordrecht. https://doi.org/10.1007/978-1-4020-9729-4_313

Wallace, William A. Prelude to Galileo. E. Reidel Publishing Co., Netherlands: 1981. Print. 52-6, 66-7, 96.