This feature issue on Light and Color in Nature focuses on the interplay of light with the landscape and other naked-eye phenomena and describes a wide range of natural optical phenomena that can be seen in our natural environment. Results are reported on the experimental and theoretical investigations undertaken to improve understanding of these phenomena.
© 2020 Optical Society of America
Why are there so many
Songs about rainbows
And what’s on the other side?
—Kermit the Frog, “The Rainbow Connection” 
The sky, with its changing colors and varied phenomena, has always been a source of fascination and wonder to humanity. Our attempt to understand what we see in the sky, and indeed the rest of the natural world, is intertwined with the general history of optics in a fundamental way. To give one small example, the study of the rainbow is deeply connected to the development of optics as a science . Blue skies, red sunsets, the green flash—even the gray of an overcast day—have all been studied with both scientific and aesthetic interest.
The “Light and Color in Nature” conferences, under various names, have been held every two to three years since 1973, to study the optics of the natural world. There have been 13 such conferences to date, taking place in locations as varied as Boulder, Colorado and Granada, Spain. They have always been international—the landscape and nature know no boundaries. They have also drawn a wide mix of disciplines: physicists, meteorologists, biologists and historians, to name a few. The conferences are small, with perhaps 30 to 50 participants each time, but anyone interested in the overarching subject of light in the landscape and natural world has been welcome to participate.
These conferences were originally inspired by Marcel Minnaert’s book Light and Color in the Outdoors , a popular explanation of the optics of the natural world, which inspired many of the conferees to write other wonderful books: Bob Greenler’s Rainbows, Halos and Glories , David Lynch and William Livingstone’s Color and Light in Nature , and Michael Vollmer’s Lichtspiele in der Luft , among others.
To quote Minnaert on the appeal of these studies: “Never think that the poetry of nature’s moods in all their infinite variety is lost on the scientific observer, for the habit of observing refines our sense of beauty and adds a brighter hue to the richly colored background against which each particular fact is outlined” . He wrote two other popular books on science in nature that have never been translated into English.
Few of us are funded for this research, which makes the conferences joyous affairs, as we are all people joined in the love of what we study. Dave Lynch organized the original conference in 1978, held in Keystone, Colorado, due to his interests in meteorological optics. It is to the credit of the organizers of the first few conferences (Dave, Bob Greenler, Bill Livingston, Alistair Frasier and others) that they recognized the need and desire for them, and were able to secure funding from the Optical Society of America and the National Science Foundation to continue them. The editors of this special issue read the papers from the special issues associated with the conferences, and recognized in them a group of like-minded people, almost at the level of family.
These “Light and Color” special issues of Applied Optics, and other journals before it, have always been a feature of the conferences. They showcase the research that the conferees present at them. In the past, they have been among the most popular of the special issues, mainly because of the pictures shown in the papers. The current issue features papers on the polarization of light scattered from beetle carapaces, the optics of arctic mirages, sky polarization during an eclipse, rainbows created by distorted droplets, to name some of the varied topics.
This special issue is being published at a time during a global pandemic when many labs have had to shut down, and many are experiencing hardships. We would like to give a nod to the fact that many of the topics presented in this special issue don’t require fancy lab equipment, but may have begun with a simple observation of a rainbow from someone’s back porch. As Minnaert said, “The phenomena [from this special issue and the Light and Color in Nature conference series] are partly things you can observe in everyday life, and partly things as yet unfamiliar to you, though they may be seen at any moment, if only you will touch your eyes with that magic wand called knowing what to look for” .
As editors of the special issue, we would like to take this opportunity to invite new researchers to participate in the next conference. The research focus of the conference is straightforward: any phenomenon under study should satisfy two criteria:
- 1) It should be some aspect of the interaction of light with the natural world, broadly defined; and
- 2) In principle, it should be visible to the naked eye (although this criterion has been slightly relaxed in the past.)
While many aspects of light and color in nature have been explored, many more remain that have not been studied to any great degree. We have had biologists interested in the optics of insect carapaces and butterfly wings, but there are surely many more examples of visual optics in the biological world. A few historians have analyzed famous atmospheric displays shown in art or in the historical record, but there must be many more to examine and theorize over. We have had one computer scientist, Henrik Jensen, who discussed how computer graphics experts render the sky and other atmospheric phenomena, but we would certainly welcome more to our group.
If you are interested in attending the next conference, or on any aspect of the science or our research, please contact any of the authors of the papers in this special issue. In particular, you can reach out to the editors of this special issue—the authors of this introductory paper. Just send us an email—we welcome you to join us!
1. P. Williams and K. Ascher, “The Rainbow Connection,” in The Muppet Movie: Original Soundtrack Recording, Atlantic Records (1979).
2. C. B. Boyer, The Rainbow: From Myth to Mathematics, Sagamore Press, New York (1959).
3. M. Minnaert, Light and Color in the Outdoors, Springer-Verlag (1992); updated English translation of De natuurkunde van ‘t vrije veld. Licht en kleur in het landschap (1937).
4. R. Greenler, Rainbows, Halos and Glories, Cambridge University Press, Cambridge (1990).
5. D. Lynch and W. Livingstone, Color and Light in Nature, Cambridge University Press, Cambridge (2001).
6. M. Vollmer, Lichtspiele in der Luft: Atmosphärische Optik für Einsteiger, Spektrum Akademischer Verlag, Heidelberg (2005).