The Ulam Spiral is a simple method of graphing the prime numbers that reveals a pattern which has never been fully explained. It was discovered by the mathematician Stanisław Ulam in 1963, while doodling on scratch paper at a scientific meeting.
Thursday, August 09, 2007
Tuesday, August 07, 2007
Monday, August 06, 2007
NYTimes on Wikimania, Chinese censorship, and other things. The collapse of mainland chinese wikipedia participation is pretty depressing. At Boston wikimania, there was nobody more enthusiastic than the handful of mainland chinese people; they were absolutely thrilled to be there.
Ancient world maps.
The De Virga world map was made around 1411. (And re-discovered in a second-hand bookshop in 1911. And stolen during an auction in 1932, and never recovered.)
It gives a fairly accurate shape of Africa, at a time when the continent had not yet been rounded by European explorers. The source of such cartographic information is unknown, although it could be Muslim traders, or possibly Chinese cartographers under Admiral Zheng He.
Zheng He was a Chinese mariner, explorer, diplomat, fleet admiral, and eunuch who from 1405 to 1433 made voyages across the Indian ocean and to the coast of Africa. His voyages and the subsequent possible abandonment (as some have argued) of maritime exploration by the Chinese emperors have become symbolic in the space advocacy community of the success and cancellation of the Apollo Program.