How Eratosthenes calculated the circumference of the Earth

One of Dan Sperber's favorite explanations belongs to Eratsthenes (276-195 BCE) who used a few local observations to calculate the circumference of the Earth to within 1% of the modern measurement. Sperber carefully walks us through Eratsthenes' calculations, then comments:

Was Eratosthenes thinking concretely about the circumference of the earth (in the way he might have been thinking concretely about the distance from the Library to the Palace in Alexandria)? I believe not. He was thinking rather about a challenge posed by the quite different estimates of the circumference of the Earth that had been offered by other scholars at the time. He was thinking about various mathematical principles and tools that could be brought to bear on the issue. He was thinking of the evidential use that could be made of sundry observations and reports. He was aiming at finding a clear and compelling solution, a convincing argument. In other terms, he was thinking about representations—theories, conjectures, reports—, and looking for a novel and insightful way to put them together. In doing so, he was inspired by others, and aiming at others. His intellectual feat only makes sense as a particularly remarkable link in a social-cultural chain of mental and public events. To me, it is a stunning illustration not just of human individual intelligence but also and above all of the powers of socially and culturally extended minds.
Sperber's article is one of one of 192 this year in response to Edge.com's annual question: "What is Your Favorite Deep, Elegant, or Beautiful Explanation."

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3 Idiots: “Aal Izz Well”

This may not be the perfect forum for a review, but the film "3 Idiots" is about education versus training, science versus engineering, fear versus hubris (and the happy medium), life and death, love and despair, laughter and tears. And it has colorful Bollywood dance numbers, too! I rented it on a whim, as it was billed as a movie about too-smart engineering students versus the educational system. I was puzzled when it began with English subtitles during the (Indian accented) English dialog. I remembered a 1990's PBS/BBC series on the English language, when some of the impenetrable-to-me accents of the U.K. had no subtitles, but the perfectly intelligible-to-me Cajun and Ebonic dialects did. But as the blend of Hindi and English became apparent, I saw the need. I loved this movie. Once one gets into the esthetic swing of Bollywood productions, it makes perfect sense when serious issues become silly dance numbers, and all characters are played as borderline caricatures. One can observe the essential cultural differences between our familiar American dilute-Christian one-life-to-live and anyone-can-become-president attitude and the Indian institutionalized attitude that reincarnation is the only way to improve your lot except through extraordinary means. Why I think this is appropriate to this forum is the take on education. The protagonist has a scientific mindset that is often at odds with engineering philosophy and even more with institutionalized education. The system of teaching to the test is questioned, as is the principle of square pegs hammered into round holes. Vocation versus avocation is central to this, and expounded toward the end. The 3 Idiots - Official Trailer has embedding disabled, but preview is fun even without subtitles. You get the idea of how English and Hindi have merged in their culture. I defy you to watch it and not have the songs "All izz well" and/or "Zoobi Doobi" stuck in your heads.

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