[math-fun] Seven-Planet Somsky Gears

Hi Mathfun friends, See here a 3D-printed version of the Seven-Planet Somsky Gears. https://www.youtube.com/watch?v=3iyO-OvIS_k https://www.shapeways.com/product/SPGDQSRLE/seven-planet-somsky-gears Someone at the Twisty Puzzles Forum asked the question "Is there a link to the arguments for the maximum number of planets?" http://twistypuzzles.com/forum/viewtopic.php?p=342755#p342755 Enjoy! Oskar