De iride – On the Rainbow

The next in the Ordered Universe workshop series will be focused on the treatise De iride, ‘On the Rainbow” by Robert Grossetese.  Although the treatise on the rainbow by Theodoric of Freiburg in the early 14th century has enjoyed more attention than Grosseteste’s the earlier treatise is the first to introduce the notion of refraction into the explanation of the physics of the rainbow. Grosseteste’s treatise also pre-dates the next attempt to provide an answer to how rainbows work by his near-contemporay Witelo. The treatise De iride  is closely related to Grosseteste’s treatment on Colour (the De colore) and the larger treatise on Lines and Angles (the De lineis). Two workshops are planned for Michaelmas Term, the first, for which a poster is attached, will take place on Thursday 18th and Friday 19th October, in Collingwood College (Dales Suite). The second will take place on Thursday 6th and Friday 7th of December. Both workshops will feature the Ordered Universe collaborative methodology, with medievalists and modern scientists working together on the text.  All are welcome; places are limited to 20.  Please register your interest with Dr Giles Gasper (

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