Autobiographical note: Despite my strong desire to do so, yesterday’s reports of a possibly habitable planet will not be discussed at length. One word though: AWESOME!!!
Benham’s top is a scientific mystery developed by a toymaker.
In 1894, English toymaker C.E. Benham discovered that a specific pattern of black lines on a white disk, when spun, would cause Fechner colours.* Not only are there Fechner colours, different people see different colours. Several sites I looked at noted that the author saw red. I happen to see green.
Technically speaking, the mystery is the mechanism behind Fechner colours, not why Benham’s disk, specifically, causes the phenomenon. It just happens that Benham’s top is the most demonstrative example. Regardless, scientists have no explanation for why the brain perceives colour when none is present.**
*Fechner colours are colours that aren’t really there and are named for the 19th century German psychologist Gustav Fechner who first studied why people see colour in rotating black and white patterns.
**For more information see the lower parts of this page.