Today’s Torygraph has a short video entitled 10 Remarkable Facts about rainbows, at 57 seconds it displays the following text:

Until the 17th Century, no one had

the faintest idea what a rainbow

was, how it got there or what it was

made of…

This is, of course, simply not true. In the 14th century the Persian scholar Kamal al-Din Hasan ibn Ali ibn Hasan al-Farisi (1267–1319) gave the correct scientific explanation of the rainbow in his Tanqih al-Manazir (The Revision of the Optics). Almost contemporaneously the German scholar Theodoric of Freiberg (c. 1250–c. 1310) gave the same correct explanation in his De iride et radialibus impressionibus (On the Rainbow and the impressions created by irradiance). The two scholars arrived at their conclusion independently of each other but both of them did experiments involving the study of light rays passing through glass spheres full of water and both scholars were influenced by the optical theories of Abū ʿAlī al-Ḥasan ibn al-Ḥasan ibn al-Haytham. Unfortunately both explanations disappeared and it was in fact first in the 17th Century that the Croatian scholar Marco de Antonio Dominis (1560–1624) once again gave an almost correct explanation of the rainbow in his Tractatus de radiis visus et lucis in vitris, perspectivis et iride.