The Universe in a Nutshell

A small sphere of dark glass, faintly rimmed with light, resting on a dark plane engraved with a unit square and the sphere's own graticule pushed flat, a fine golden ring at the sphere's crown, and one hairline thread of light running from the ring's edge, through a point on the sphere, to its image on the plane — the stereographic projection, with a slow spiral tracing the point's climb

Grab the light: drag anywhere on the plane inside the drawn square, or on the lower half of the sphere, and the thread follows the pointer, the point on the sphere and its image on the plane moving together by the same projection. Release to let it ease back into its slow ambient spiral, without jumping. Drag anywhere else in the scene to turn the view around the sphere; double-click to return to the composed view. With the figure focused, arrow keys nudge the point on the plane, further with Shift held.

Fig. VIII — Stereographic projection here symbolises the emanation from Infinity into Finitude, from Unity to Multiplicity. Each point on the sphere's surface corresponds precisely to one point on the 2 dimensional plane, except for one, the source, the North Pole. In this sense, the sphere is more than the plane. It is the plane missing a point: that point is Infinity.