Newton’s experiment remains almost insultingly simple. Sunlight, a darkened room, a glass prism. The conclusion was unavoidable. Colour belonged to light itself. The prism merely made it visible.

The net of a 3D shape is what it looks like if it is opened out flat. There are many types of nets for the different 3D shapes. A net is made from polygons that can be folded and joined to make a ...