Image Credit Flickr User ElDaveAlthough the armillary sphere was superseded (technologically speaking at least) in the seventeenth century by the European telescope, surviving examples remain objects of fascination and wonder. The first question, of course, is what does it do? The second is invariably who invented it?
This scientific leap of the imagination is something quite astounding, particularly given the times in which this leap was made.
On the left you can see the Earth rotating within a comparatively small-diameter Earth-centered celestial sphere.
Illustrated here are the stars (white), the ecliptic (red), and lines of right ascension and declination (green) of the equatorial coordinate system.
First Image Credit Flickr User Jaci XIII
Earth within ccelestial sphere - Wikimedia