Sangaku: The Sudoku of the 17th century

Behold an ancient Japanese “Sangaku” table — the Sudoku of the 17th century.

Sangaku emerged during the 100-year period that Japan forcibly cut itself off from West, allowing only one Dutch ship a year to dock. The cultural isolation did some weird things to the country’s mathematicians. Because they never heard about calculus — which was developed in Europe — they developed brute-force ways of solving classic calculus problems, such as how many circles of a particular size fit in a square. They’d draw the enormous, sprawling solutions out on beautifully illustrated wooden tables, which they regarded as religious offerings. (I love it: Using math to praise God. Man, wouldn’t it be nice if more religious conservatives in the US made that connection? It’s quite a venerable once, too, since many historic mathematicians — most particularly Newton — regarded math as the language in which God spoke.)

Anyway, Sangaku fell into disrepute during the 20th century, but Tony Rothman, a Princeton Nobel nominee, is helping spearhead a movement to restore what he calls the sudoku of the 17th century. Like Sudoku, Sangaku was based in principles so simple that children could solve them, as Rothman says in this story:

“Some of the tablets feature solutions provided by 12-year-olds,” he said. “But that doesn’t mean they were easy. Today’s high school geometry problems tend to require only five or six lines to solve, whereas the old problems often demand pages and pages of work. Sangaku were more like math Olympics problems, or the sort of thing your teacher might have put on the wall for extra credit.”


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I'm Clive Thompson, a writer on science, technology, and culture. This blog collects bits of offbeat research I'm running into, and musings thereon.

Currently, I'm a contributing writer for the New York Times Magazine and a columnist for Wired magazine. I also write for Fast Company and Wired magazine's web site, among other places. Email or AOL IM me (pomeranian99) to say hi or send in something strange!

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September 26, 2008 » 01:57 PM

From an interview with ethnobotanist and anthropologist Wade Davis:

One of the cultures you celebrate in Light at the Edge of the World is the Inuit. What do you most admire about them?

Davis: The Inuit didn’t fear the cold; they took advantage of it. During the 1950s the Canadian government forced the Inuit into settlements. A family from Arctic Bay told me this fantastic story of their grandfather who refused to go. The family, fearful for his life, took away all of his tools and all of his implements, thinking that would force him into the settlement. But instead, he just slipped out of an igloo on a cold Arctic night, pulled down his caribou and sealskin trousers, and defecated into his hand. As the feces began to freeze, he shaped it into the form of an implement. And when the blade started to take shape, he put a spray of saliva along the leading edge to sharpen it. That’s when what they call the “shit knife” took form. He used it to butcher a dog. Skinned the dog with it. Improvised a sled with the dog’s rib cage, and then, using the skin, he harnessed up an adjacent living dog. He put the shit knife in his belt and disappeared into the night.

September 25, 2008 » 11:21 AM
“Video from a camp north of Toronto in December 2005 shows a car spinning around in a nearby, snow-covered parking lot. Prosecutors characterized that as special driver training but the defense, and many outsiders, said it was nothing more than “cutting doughnuts,” a favorite winter pastime of young Canadian motorists.” - A key piece of evidence submitted in the trial of a gang of alleged young Canadian terrorists.

September 24, 2008 » 11:21 PM
“Life imitates art imitating life: just thought a gnat crawling across my monitor was part of a Flash-based ad. I clicked it.” - A Tweet from Bill Braine.

September 24, 2008 » 02:37 PM
“Funniest FB friend request ever: “Twitter friend hoping to get to second base (Facebook!) ;-).”” - A recent Tweet by Pistachio

September 24, 2008 » 12:28 PM
Chinese powdered-milk crisis creates a new market: The return of the wet nurse

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