THE RAINBOW BRIDGE:
Rainbows in Art, Myth, and Science

©RAYMOND L. LEE, JR.
and
ALISTAIR B. FRASER

Penn State Press (University Park, PA), 2001
and SPIE Press (Bellingham, WA)
ISBN 0-271-01977-8

The research for, writing of, and editing of this book was generously supported by U. S. National Science Foundation grant numbers ATM-9820729, ATM-9414290, ATM-8917596, and ATM-8607577.

CONTENTS

CHAPTER  p. # 
Preface ix 
Acknowledgments xiii 
1 The Bridge to the Gods:  Rainbows in myth & legend
2 Emblem and Enigma:  Rainbows in art (before 1650) 34 
3 The Grand Ethereal Bow:  Rainbows in art (after 1650) 68 
4 Optics and the Daughter of Wonder:  Ancient rainbow science;
    Some common rainbow features in art & nature
100 
5 Unweave a Rainbow:  Medieval rainbow science 136 
6 Beyond the Medieval Rainbow:  Renaissance & later rainbow science 168 
7 Color the Rainbow to Suit Yourself:  The rainbow & color theory 206 
8 What Are "All the Colors of the Rainbow"?:
    Cloudbows & supernumeraries; Seeing & measuring rainbow colors
242 
9 The End of the Bow:  Other varietal rainbows & rainbow features 274 
10 Sell It with a Rainbow:  Rainbows in commerce;
    The rainbow in modern science & art
300 
Appendix:  A field guide to the rainbow; About color terminology 321 
Endnotes 327 
Bibliography 367 
Index 383 

PREFACE

What, then, in optics is most difficult of demonstration?
Is it not, perhaps, the explanation of the form, size, and color of the rainbow,
seeing that there enters into its production a consideration of the entire field of optics,
namely, vision, light, reflection, and transparent bodies, concerning which
many have written; but no one has as yet given a satisfactory explanation?
Francesco Maurolico, "Problems in the Field of Optics and the Rainbow" (1567)

   Who among us has not admired the majestic beauty of a rainbow arching silently across a storm's wake? Vivid and compelling, this image recalls childhood memories, venerable folklore, and perhaps some half-remembered science lessons. Yet except for such fleeting, transcendent moments, the rainbow seems an unlikely candidate for emboldening, terrorizing, and fascinating our species. Nevertheless, across the millennia the rainbow has been venerated as god and goddess, feared as demon and pestilence, trusted as battle omen, and used as an optical proving ground. The rainbow image is woven into the fabric of both our past and present, but its very familiarity today renders it nearly invisible. For all of us, a fresh look at the rainbow seems well worthwhile, especially given that the bow spans some modern divides between the arts and sciences.

   Because almost every society has considered the rainbow its private preserve, not surprisingly the bow has assumed many guises. The optimism that we associate with the rainbow is hardly universal. For example, the ancient Greeks named the rainbow Iris, and she became the bearer of the gods' often dread messages of war and retribution. Some societies see the rainbow as an ominous serpent arching across the sky, while others imagine it to be a tangible bridge between the gods and humanity. In Judeo-Christian culture, this literalism has been reworked so that the rainbow is a symbolic bridge to the divine, a sign of God's covenant. We too will use the rainbow as a bridge, but this time as a link among the disparate perceptions that artists, scientists, and mythmakers have of the natural world.

   Throughout history, the rainbow is seen primarily as a symbol -- whether of peace, covenant, or divine sanction -- rather than as a part of nature. As a symbol, rather than a natural phenomenon, the rainbow can depart quite radically from nature. Advertising art can satisfy (or create) our collective desire for emblems, and in so doing, it has absorbed the rainbow, along with many other aspects of nature. As an object of fantasy, the rainbow in advertising can take on any appearance, freely mixing its colors, or consorting with mermaids and unicorns. Our myths remain as vigorous as our science.

   Francesco Maurolico's 16th-century rainbow theory is an apt metaphor for the bow itself -- an incomplete image that tantalizes with alternating brilliance and obscurity. Yet whatever his faults as a student of the rainbow, Maurolico poses exactly the right question above. The rainbow spans all of the optical world that he knew and much of ours. In fact, from antiquity to the 19th century, the rainbow played a vital role in both inspiring and testing new ideas about the physical world. Although today we understand the rainbow's underlying optics fairly well, its subtle variability in nature has yet to be fully explained. Many of Maurolico's questions have been answered to date, but certainly not all. How do we address them?

   To begin with, our chapters are organized thematically and, where useful, chronologically within those themes. For example, Chapter 1 gives an overview of rainbow mythology from across the world, while Chapters 2 and 3 outline the rainbow's art history. The rainbow's scientific history from Aristotle to Isaac Newton is discussed in Chapters 4-6, while Chapter 7 considers its influence on color theory in Western science and the arts. In Chapters 8 and 9, we look at some of the natural rainbow's subtler features and how they influenced optical theory after Newton. Chapter 10 examines the rainbow's status today, whether in advertising, the fine arts, or the sciences. Within each chapter, we illustrate the rainbow's complex story with historical or scientific sketches that are devoted to particular persons or ideas. In each of these sketches we relate some feature of the natural rainbow to its human reflection, whether written or painted. From Chapter 7 onward, we add to these sketches our own rainbow research whenever this helps explain the bow's history, mythology, or optics. For ready reference, the Appendix summarizes some basic rainbow features and explanations that the main text describes in more detail.

   Because we believe that bridges can be built between different cultural visions of the rainbow, we offer vignettes on rainbow paintings in most chapters, including those nominally devoted to rainbow optics. Our goal here is not to cast artists in the role of scientists, but rather to emphasize the shared problems of observation that the two groups face -- and how they often arrive at very different answers. (We can easily imagine that art historians writing this book might add some scientific sidebars to their chiefly historical tale.) Just as the two ends of a real bridge may arise from very different bases, so too the rainbow bridge may span very different perceptions of the same rainbow feature. Similarly, we know that some historians of science may question our labeling as "errors" the now-rejected features of rainbow theories from earlier centuries. In fact, identifying our predecessors' errors is not 20th-century scientific chauvinism, for we keenly appreciate that scientific ideas always evolve within (and are shaped by) particular cultural contexts. Furthermore, many older theories have some quite plausible features. However, their very plausibility can mislead readers newly versed in modern rainbow theory, so we offer some guideposts along the way. Perhaps rainbow bridges can help span modern academic divides.

   Our book is intentionally eclectic -- we are offering an illustrated survey of the rainbow's place in science, mythology, and art, not an exhaustive monograph on one of those stories. For such specialist treatments, we recommend Carl B. Boyer's The Rainbow or Paul D. Schweizer's recent paper "John Constable, rainbow science, and English color theory" (complete citations in the Bibliography). Rather than attempt to follow every twist and bend of the rainbow's course through history, we instead want to traverse bridges between the various roles that the rainbow has played. As scientists, teachers, and devotees of the rainbow, we will consider it high praise indeed if we inspire readers to look at the rainbow anew.

Raymond L. Lee, Jr.
U. S. Naval Academy

Alistair B. Fraser
Pennsylvania State University (Emeritus)

(Opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.)