I am fascinated by the ebb and flow of insight, discovery, writing, progress in this project. Like so much science itself, sometimes ideas need simply to develop quietly on their own, at other times they are ready for serious up-front work. So the realisation of Hannah Smithson when at the Porto workshop that Grosseteste’s identification of his colour coordinates with the dimensions of rainbows and “different types of rainbows” might lead to co-ordinate systems with spiral structure, hss led to two weeks (prior to the next JOSA deadline – deadlines help too!) of intense and fruitful work (by far mostly on Hannah’s part out cheered on by the rest of us). This involved a lot of serious physical optics (sourced from world expert Philip Laven), mathematical perception theory (Hannah)and a totally trivial link to the rather bijou “log-polar” co-ordinate systems (me) – but for the first time the De Colore puzzle looks like having a satisfactory solution. More anon with diagrams – very beautiful ones.