- Ulloa's bow
- Also known as glory. The eponym Ulloa's bow refers to the Spanish naval officer, explorer, and astronomer Antonio de Ulloa y de Torre-Giral (1716-1795). It is used in meteorology to denote a * physical illusion consisting of one or more colourful rings or arches, which have their colours arranged in the reverse order of those in a * rainbow. Sometimes these colourful rings or arches can be seen within a white luminous ring or arch called an * Ulloa circle. Both phenomena are sometimes seen in mountainous regions, typically in foggy weather, while facing a direction opposite the Sun (i.e. the antisolar point). In the past this used to be a rare experience worthy of publication. However, today Ulloa's bow is a common phenomenon seen by airline travellers looking down upon clouds opposite the Sun. Ulloa is commonly credited with having been the first to record Ulloa's bow and the Ulloa circle, after having observed them during an expedition in what is now Ecuador, between 1735 and 1739. Although the mediation of Ulloa's bow is not fully understood, a central part is attributed to the interaction of sunlight and droplets of water less than 25 im in radius suspended in the air. When Ulloa's bow is accompanied by a * Brocken spectre, the term * Brocken bow is used. Because of its lack of a tangible substratum in the extra-corporeal world, Ulloa's bow is also classified as a * fiction illusion.ReferencesJuan, J., de Ulloa, A. (1748). Relacion historica del viaje a la America Meridional hecho de orden de su Majestad. Madrid: Juan de Zuniga.Lynch, D.K., Futterman, S.N. (1991). Ulloa's observations of the glory, fogbow, and an unidentified phenomenon. Applied Optics, 30, 3538-3541.Lynch, D.K., Livingston, W. (1995). Color and light in nature. Cambridge: Cambridge University Press.
Dictionary of Hallucinations. J.D. Blom. 2010.