The Green Ray: a doubled double image

Visual Notes

The green ray is only perceivable due to mirages, often mistaken or claimed as miracles. It is a projection of the real, like the allegoric shadows projected in the cave. However, such indiscernibility leads to open up knowledge towards opportunity/chance, the apparent and to regain a lost value on cosmological rites.

    The Green Ray,[1] (mis)described as green flash or green dot, is an astronomical phenomenon, perceived at the first or last glimpse of the sun light in the horizon, that appears as a vivid and astonishing green ray. It is rarely observed, taken up and dealt with in several myths, legends and other assumptions[2], which often have their origin in western coasts, once the best scenario for its observation happens while observing the sun set, with a clear and unobstructed view, that is, towards the west horizon.  

Its either scientific[3] or fiction-based references[4] were, as it seems, firstly introduced uniquely by the European culture, once first publications mentioning it appeared in Europe. Even though there are reported green ray observations during expeditions[5] in other geographical locations, such as Indian sea or in African territories, they all appeared some decades later and were always reported by European navigators that already had previous knowledge about it.  

As a simple explanation, it consists in an astronomical refraction effect of the first or last observed sun ray (during its arising or setting), bended by the curvature of the Earth, thus happening when the sun itself is actually out of the eye view, that is, invisible.

   Although, this explanation by the scientific community was dubious until last century and even nowadays it is often mistaken, as an exclusively optical effect and not understood as a real physical phenomenon.[6] (the references below list three letters by first Cassini experiments on refraction, being the third letter (without date) – Epistolae Tertia – an argument against Mengoli’s definition of a Table of Refractions for every degree of altitude, which Cassini claims to be false. Cassini’s theories were later reformulated by Huygens and other scientific articles (see footnote 13). Cassini’s works do not concern directly with the green ray, but it demonstrates the problematic in defining terrestrial refraction, and consequently the causes of the green ray, which persisted unclear in the scientific community, until the XX century[7]. Only at the beginning of the XX century, with the appearance of new mediums, such as photography and video, it became more evident that the theory referring to the green ray as a strict optical effect (being until then justified with the retina cells extra-sensibility to the green colour) was not correct[8].  In fact, it is partly true, as green is better perceived by the human eye than other colours of the light spectrum. Although, the same green colour was finally registered by cameras, proving it was not only a naked eye effect. Still, it has the potential of a trompe-l’oeil, with all its illusionary tricks, once what is in fact observable is always a mirage. The green ray is as real, as it is a visual effect. Despite being an astronomical phenomenon, it requires the qualities of affection to observe it, in the terms the observer must get attached to a landscape, in this case, the adaptation to abstract landscape, in order to recognize it. The green ray has a complex form of appearance and it constantly requires new ways of observation.

  By being a rarely observed phenomenon, the challenge of understanding it, requires from its observer a constant reformulation of strategies. Such experiments are in my opinion of major importance for an utterly reflection on new strategical approaches with visible and invisible matters. This can be particularly valuable for science, as a demanding acceptance of indiscernible elements, and for the arts, by regarding at forms of activations, through embodied knowledge and mutable processes, that promote new aesthetics.   

[1] Meinel, A. and M. (1983) Sunsets, twilights, and evening skies. Cambridge University Press, pp.21

[2] Fraser, A. B. (Jan., 1981) “To see a dazzling festival of light, just raise your eyes,” Smithsonian 11, pp. 72–79

Botley, C. M. (1971) “The green ray,” Weather 26, pp. 354–357

Sitwell, O. (1940) Escape with Me! An Oriental Sketch-Book. Harrison-Hilton Books, New York, pp. 20–21.

[3] Corliss, W. R. (1984) Rare Halos, Mirages, Anomalous Rainbows and Related Electromagnetic Phenomena. Sourcebook Project, Glen Arm, MD

[4] Verne, J., et al. (2017). Le Rayon vert (illustrate), Clap Publishing, LLC

[5] Notes: This observation was made west of the southern part of Ceylon, on board the S.S. "Tosari", 12 September 1924, 6.15 p.m.

Verschuur, A. D. (1926) “Groene straal”. De Zee 48, pp. 446–448

Notes: Green ray report observations in Tibet

Knight, G. O. E. (1923) “Atmospheric optical phenomenon”. Geographical J. , pp. 61, 390

Swift, H.  and Davies, D. A. (1951) “Green flash, Indian Ocean”. Marine Observer, pp. 21, 218

[6] Cassini, J. D. (1672) “Three letters of Jo.Dominicus Cassinus, concerning his Hypothesis of the Suns motion, and his doctrine of Refractions; printed at Bononia in 4°,” Phil. Trans. Roy. Soc. Lond. 7, No. 84, 5001–5002 (

Cassini, J. D. (1692) “De solaribus hypothesibus et refractionibus epistolæ tres,” in Miscellanea italica physico-mathematica. G. Roberti, ed. Typographia Pisariana, Bononiae, pp. 281–340.

Riccioli, I. B. (1665) Astronomiæ Reformatæ Tomi Duo. Ex Typographia Hæredis Victorij Benatij, Bononiæ

[7] Huygens, C. (1945) Treatise on Light. University of Chicago Press, Chicago

[8] Notes: first known color photographies by Maurice de Kerolyr.

Touchet, Em.  (1931) “La photographie en couleurs du `Rayon Vert',” La Nature 59:2, No. 2862, pp. 100-104