Today we have a fan submission to the show. Darren Lundrum from The Eternal Prototyper . Follow him up on twitter as well. He has some mad music skills and you should go and check his stuff out! The links mentioned in the cast: http://www.scientificamerican.com/media/pdf/Slide_rule.pdf http://www.joh.cam.ac.uk/cms_misc/media/library/build_your_own_astrolabe.pdf Less