Amidst all the lurking iPhone killers, we seem to have forgotten the one that doesn’t even use batteries: the Astrolabe was the must-have device of the 13th century, with the capability of telling time, mapping the night sky, and hundreds of other functions that were high tech for the time.The computer went through a number of versions since it was first developed in the 6th century AD, but it’s design remained basically the same: a disc and a movable arm, not unlike today’s hard drives. Before Hubble (or Google Maps), it was the best device for charting heavenly bodies and navigating. In 1391, when Geoffrey Chaucer’s son kept bugging him to teach him how to use one, the poet wrote a kind of Astrolabe for Dummies, because “as wel considre I thy besy praier in special to lerne the tretys of the Astrelabie.”At TED, “innovation thinker” Tom Wujec shows off the ancient gadget.