C L I N I C A L A N D E X P E R I M E N T A L OPTOMETRYThe Min Min light and the Fata Morgana Pettigrew COMMENTARY The Min Min light and the Fata Morgana An optical account of a mysterious Australian phenomenon Clin Exp Optom 2003; 86: 2: 109–120 John D Pettigrew BSc(Med) MSc MBBS Background: Despite intense interest in this mysterious Australian phenomenon, the FRS Min Min light has never been explained in a satisfactory way. Vision Touch and Hearing Research Methods and Results: An optical explanation of the Min Min light phenomenon is of- Centre, University of Queensland fered, based on a number of direct observations of the phenomenon, as well as a field demonstration, in the Channel Country of Western Queensland. This explanation is based on the inverted mirage or Fata Morgana, where light is refracted long distances over the horizon by the refractive index gradient that occurs in the layers of air during a temperature inversion. Both natural and man-made light sources can be involved, with the isolated light source making it difficult to recognise the features of the Fata Morgana that are obvious in daylight and with its unsuspected great distance contribut- ing to the mystery of its origins. Submitted: 11 September 2002 Conclusion: Many of the strange properties of the Min Min light are explicable in terms Revised: 2 December 2002 of the unusual optical conditions of the Fata Morgana, if account is also taken of the Accepted for publication: 3 December human factors that operate under these highly-reduced stimulus conditions involving a 2002 single isolated light source without reference landmarks. Key words: Channel Country, Fata Morgana, inverted mirage, Min Min light, temperature inversion Accounts of the Min Min light are a col- Maureen Kozicka1 spent two years re- accounts of Min Min lights and my optical ourful and inextricable part of Austral- searching Min Mins before her untimely explanation of them are based on those ian outback folklore that seem to have re- death and produced the only book de- experiences and on some investigations sisted many attempts at their explanation. voted to the phenomenon. Although she and an experiment designed to reproduce In the Channel Country of western interviewed many who had seen the light the phenomenon under field conditions. Queensland where the majority of and spent much time in the Channel I will begin with a brief description of sightings of the Min Min have taken place, Country, Kozicka1 never saw the phenom- the Min Min light phenomenon, summa- the town of Boulia has linked its public enon herself and was not able to reach any rising the key observations of others, with image to the phenomenon and thereby firm conclusions about it. I was lucky an emphasis on the ‘notorious’ features tried to improve its attractiveness as a enough to witness the phenomenon on a that excite so much emotion in virtually tourist destination. The following notice number of occasions while on field trips all those who have witnessed it. Next, I will is found in the town: to study the nocturnal activities of the let- describe my own encounters with the phe- ‘Min Min light, this unsolved mystery is a ter winged kite, Elanus scriptus, in classical nomenon, including some field measure- light that at times follows travellers for long Channel country; namely, the upper ments of its distance from the observer, as distances—it has been approached but never reaches of the Diamantina and Georgina well as an experiment on the plains that identified.’ rivers in Western Queensland. The present successfully reproduced the major features Clinical and Experimental Optometry 86.2 March 2003 109 The Min Min light and the Fata Morgana Pettigrew of the phenomenon. Finally, I will discuss Brightness and colour anyone unfamiliar with the concept of the findings in the light of the hypothesis Brightness varies greatly in different re- parallax and with the moon’s great dis- that the Min Min is a refractive phenom- ports, from dim lights similar to a second tance. Nevertheless, even when the ob- enon, in the same class as the inverted magnitude star, to brilliant sources that are server is stationary, it is clear that the Min mirage, or Fata Morgana, except that it able to illuminate objects in the landscape Min can sometimes change its apparent occurs at night. This explanation may have and to cast bright shadows of the observer location very quickly. Some of these rapid been overlooked largely because the noc- onto building walls. Most reports involve changes seem to be linked to the observ- turnal Min Min phenomenon involves an white light but changing colour is not unu- er’s own actions but clear examples are isolated light source and the relationship sual, with gradual changes through the known where the movements of the light of it to other visual landmarks cannot be spectrum from red to green and back rapidly illuminate different features of the determined, as can more readily occur again. Blue Min Mins are rare compared landscape in succession, an effect that can with a daytime Fata Morgana. Such a sin- with green, yellow and red ones. be explained only if the light source itself gle small light source, at night, without any is changing. reference points, may not readily reveal Animation the diagnostic features of this kind of mi- The light seems to have a mind of its own, Distance rage in the way that would make it easily approaching closely at times and retreat- Reports vary widely concerning the dis- recognisable in a landscape during day- ing to the distance at other times. This tance at which the Min Min light is per- light. I also discuss the subjective aspects aspect of the behaviour of the Min Min ceived. Changes in the apparent distance of this phenomenon in the light of work light is literally hair-raising and the source of the light are the source of the most on how visual perception deals with am- of considerable emotion that may inhibit unnerving aspect of the light, which can biguous or incomplete information. These observers from telling their experiences appear to approach within a metre or two, internal, subjective aspects vary with the to a stranger. Even hardened residents of only to recede rapidly to what appears to individual observer and assume greater the Outback—if interviewers are fortunate be many hundreds of metres, sometimes importance for unfamiliar visual events to be able to overcome the residents’ re- linked to the observer’s own movements where there are few supporting visual luctance to talk about Min Mins—usually or thoughts. As the light is usually a single clues, as occurs with the Min Min. admit to being terrified by these apparent source without any nearby reference land- movements of the light, which seems to marks, estimates of its distance are diffi- dance erratically in all three axes and can cult and subject to error, particularly by DESCRIPTION OF THE MIN MIN sometimes move smoothly and swiftly over observers not familiar with the concepts LIGHT very large distances. On occasions, a sin- of parallax and angular subtense. Like the The following summary is based loosely on gle Min Min light has been observed to moon illusion, where the same angular the many descriptions collected by split into two independent lights. In many subtense is attributed to a larger physical Kozicka1 and my own experience with five stories, the light moves suddenly just as the size when the moon is perceived to be fur- separate sightings. These are meant to be emotion of the observer peaks or the ob- ther away (for example, when seen in re- an introduction to this varied phenom- servers themselves make a move. Some lation to adjacent buildings or trees on the enon, rather than a rigorous account, so have reported a sudden disappearance horizon), the disorienting aspects of Min that the reader can have a background for when a rifle shot was fired at the light. Min lights may often result from a misper- the specific accounts that follow. ception of its distance. Velocity Angular size, shape and position A favourite response to sightings of a Min Sound Viewed through binoculars, the light is Min in the Outback is to give it a speed- Virtually all reports of the Min Min light often seen to be a fuzzy, roughly circular test, whether by horse or motor vehicle. indicate that it is silent, unaccompanied disc, a fraction of a degree of arc in diam- Min Mins always pass these tests with fly- by any sound. eter (that is, usually seen to be smaller than ing colours, apparently keeping up effort- the diameter of a full moon, which is 0.52 lessly even when the observer attains When and where of sightings degrees of arc), rather than a point source speeds up to 120 kilometres per hour. The open plains of the Channel Country of light like a star. The fuzzy edges are usu- However, note that these measurements are the legendary best site for encounter- ally in rapid motion, like a swarm of bees. make a presumption that the light is lo- ing Min Min lights but reports have been While there are rare reports of Min Min cated relatively nearby, an assumption filed from virtually every part of Australia, lights high overhead for short times, espe- tested below. If the light were situated at a including seashores and over water. In the cially when the terrain has hollows, the great distance, its ability to keep up with a Channel Country, sightings are distributed majority of accounts describe the light as high-speed vehicle is not so surprising.