Friday, May 13, 2005

Jacob Bronowski, Galileo . . . and me dragging along behind . . .

As an undergraduate at Baylor University, I studied in the Honor's Program, which offered 'accelerated' courses for students who SAT or ACT scores were high enough. Don't be impressed, though, for I think that my score just barely made the minimum.

I was reminded of this program because in looking over examples of science writing in Baker's Practical Stylist, I came upon an essay by Jacob Bronowski: "The Reach of Imagination." This was first published in Proceedings of the American Academy of Arts and Letters, 1967, volume 17. Some of you may remember Bronowski as the humanistic scientist who made the Ascent of Man series, which consisted of a book and a sequence of accompanying videos exploring the development of scientific thought within its cultural context (and a whole lot better than anything Carl Sagan ever attempted). I had the privilege of experiencing the entire series along with the book because the Honor's Program required us to take a course with the book as text, the videos as lectures, and extra sessions as occasions for discussion.

Despite all of that and all of my studies in the history of science at Berkeley, only today did I finally understand a thought experiment by Galileo -- and only because I happened to read a paragraph by Bronowski early this morning. Galileo took Aristotelian assumptions about falling bodies and uncovered a problem. If heavier objects fall faster than lighter objects -- as Aristotle claimed (and which seems intuitively obvious until modern science tells us "Not so!") -- then what happens if a heavier object and lighter object are bound together by a string and allowed to fall? The lighter object, if Aristotle is right, will be a 'drag' on the heavier object, causing it to fall more slowly. This produces a contradiction, as described by Bronowski:

"[T]he string between them has turned the two balls into a single mass which is heavier than either ball -- and surely (according to Aristotle) this mass should therefore move faster than either ball? Galileo's imaginary experiment has uncovered a contradiction; he says trenchantly, 'You see how, from your assumption that a heavier body falls more rapidly than a lighter one, I infer that a (still) heavier body falls more slowly.' There is only one way out of the contradiction: the heavy ball and the light ball must fall at the same rate, so that they go on falling at the same rate when they are tied together" (Baker, Practical Stylist, 294).

"So that's what Galileo meant!" was my morning exclamation. I don't know how many times in my long years of study that I've seen this thought experiment alluded to, but only today did I finally understand it.

The Honor's Program may have been 'accelerated,' but understanding this simple argument by Galileo took me 30 years.


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