What Galileo already knew about physics education?

As I’ve been digging further into Galileo’s Two New Sciences, I’m realizing just how well Galileo understood how difficult it was for humans to learn and understand complex ideas, and how necessary it was to explicitly discuss necessary prior knowledge, subtle mis-interprations, misconceptions, arguments, epistemology, evidence, etc. In this sense, Galileo already knew much of we know about physics education.

Can you imagine if a physics textbook we wrote today, paused to have a character say things like what’ I’ve quoted below?

On the importance of prior knowledge and cognitive load

“Your demonstration proceeds too rapidly and, it seems to me, you keep on assuming that all of Euclid’s theorems are as familiar and available to me as his first axioms, which is far from true…”

On acknowledging common difficulties

“This is one of the difficulties which I also at the beginning, experienced, but…”

On “misconceptions” in process of learning

“I am one of those who accept the proposition, and believe that a falling body acquires force [vires] in its descent, its velocity increasing in proportion to the space, and that the momentum [momento] of the falling body is doubled when it falls from a doubled height; these propositions, it appears to me, ought to be conceded without hesitation or controversy.”

On argument, epistemology, and the role of evidence:

“Your words are very plausible; but I hope by experiment to increase the probability to an extent which shall be little short of a rigid demonstration.”


“I would like to have been present at these experiments; but feeling confidence in the care with which you performed them, and in the fidelity with which you relate them, I am satisfied and accept them as true and valid”

On tentative nature of scientific knowledge (even definitions)

“We must add to the old definition (which defined steady motion simply as one in which equal distances are traversed in equal times) the word “any,” meaning by this, all equal intervals of time; for it may happen that the moving body will traverse equal distances during some equal intervals of time and yet the distances traversed during some small portion of these time-intervals may not be equal, even though the time-intervals be equal.”

And this is just one of my favorites:

“You present these recondite matters with too much evidence and ease; this great facility makes them less appreciated than they would be had they been presented in a more abstruse manner.”

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