IBG 1032
`(cid:19)(cid:19)(cid:19)(cid:20)(cid:3)(cid:3)(cid:3)(cid:3)(cid:3)(cid:3)(cid:3)(cid:3)(cid:3)(cid:3)(cid:3)(cid:3)(cid:3)(cid:3)(cid:3)(cid:3)(cid:3)(cid:3)(cid:3)(cid:3)(cid:3)(cid:3)(cid:3)(cid:3)(cid:3)(cid:3)(cid:3)(cid:3)(cid:3)(cid:3)(cid:3)(cid:3)(cid:3)(cid:3)(cid:3)(cid:3)(cid:3)(cid:3)(cid:3)(cid:3)
`CBM of U.S. Patent No. 7,212,999
`
`

`
`·rufte
`
`'
`
`c
`
`8
`
`GRAPHICS
`
`P.RE SS
`
`0002
`
`

`
`Also available from Graphics Press:
`
`Edward R. Tufte
`The Visual Display of
`O!:!_antitative Iriformation
`
`"A landmark book, a wonderful book"
`Frederick Mosteller
`
`"A tour de force"
`John W. Tukey
`
`"One of the best books you'll ever see"
`Datamation
`
`"The century's best book on statistical graphics"
`ACM Compt;ting Reviews
`
`"Stunning, a classic"
`Optical Engineering
`
`"A visual Strunk and White"
`The Bosto11 Globe
`
`"A beautiful, brilliant book"
`Mathematical Monthly
`
`The Visual Display of Quantitative Information
`$40POSTPAID
`
`Envisioning Information
`$48 POSTPAID
`
`GRAPHICS PRESS
`PosT OFFICE Box 430
`CHESHIRE, CoNNECTICUT 06410
`
`0003
`
`

`
`0004
`
`

`
`Two paintings on silk depicting .Deshirna
`Island, a view from the Bay (top), a view
`from Nagasaki (bottom), circa r86o.
`
`0005
`
`

`
`Edward R. Tufte
`
`Envisioning Information
`
`Graphics Press · Cheshire) Connecticut
`
`0006
`
`

`
`Copyright© 1990 by Edward Rolf Tufte
`
`PuBLISHED BY GRAPHics PREss
`PosT OFFICE Box 430, CHESHIRE, CONNECTICUT 06410
`
`All rights to illustrations and text reserved by Edward Rolf Tufte
`
`Printed in the United States of America
`
`Third printing, with revisions, December 1992
`
`0007
`
`

`
`Contents
`
`EscAPING FLATLAND
`
`12
`
`MICRO/MACRO READINGS
`
`37
`
`LAYERING AND SEPARATION
`
`53
`
`S MALL MULTIPLES
`
`67
`
`COLOR AND INFORMATION
`
`8I
`
`NARRATIVES OF SPACE AND TIME
`
`97
`
`EPILOGUE
`
`I2I
`
`0008
`
`

`
`for my teacher) Inge Druckrey
`
`for my parents) Edward E. Tufte and Virginia James Tufte
`
`and for Moshe) Tanya) Charlie) Natasha) Babar) and Frida
`
`0009
`
`

`
`Introduction
`
`THE world is complex, dynamic, multidimensional; the paper is static,
`flat. How are we to represent the rich visual world of experience and
`measurement on mere flatland?
`
`This book celebrates escapes from flatland, rendering several hundred
`superb displays of complex data. Revealed here are design strategies for
`enhancing the dimensionality and density of portrayals of information(cid:173)
`techniques exemplified in maps, the manuscripts of Galileo, timetables,
`notation describing dance movements, aerial photographs, the Vietnam
`Veterans Memorial, electrocardiograms, drawings of Calder and Klee,
`computer visualizations, and a textbook ofEuclid's geometry.
`
`Our investigation yields general principles that have specific visual
`consequences, governing the design, editing, analysis, and critique of
`data representations. These principles help to identify and to explain
`design excellence-why some displays are better than others.
`
`Charts, diagrams, graphs, tables, guides, instructions, directories, and
`maps comprise an enormous accumulation of material. Once described
`by Philip Morrison as "cognitive art," it embodies tens of trillions of
`images created and multiplied the world over every year. Despite the
`beauty and utility of the best work, design of information has engaged
`little critical or aesthetic notice: there is no Museum of Cognitive Art.
`This book could serve as a partial catalog for such a collection. Like my
`previous study, The Visual Display of Quantitative Information, which
`derives theoretical counsel from the classics of statistical graphics, this
`book arrays exemplary designs-this time over a broader spectrum, for
`all types of information.
`
`To envision information-and what bright and splendid visions can
`result-is to work at the intersection of image, word, number, art.
`The instruments are those of writing and typography, of managing
`large data sets and statistical analysis, of line and layout and color.
`And the standards of quality are those derived from visual principles
`that tell us how to put the right mark in the right place.
`
`0010
`
`

`
`IO
`
`Finally, in reading the words and drawings, note that:
`
`Many of the illustrations have been edited and redrawn (as indicated
`in the citations) in order to repair battered originals, to make new color
`separations, and to improve the design. Primary sources-the themes for
`my variations-are always noted.
`
`The illustrations repay careful study. They are treasures, complex and
`witty, rich with meaning. The text, I do hope, is of similar character,
`with every word meant to count; all in all, the reader should proceed
`most slowly through these bountiful and condensed pages.
`
`The principles of information design are universal-like mathematics(cid:173)
`and are not tied to unique features of a particular language or culture.
`Consequently, our examples are widely distributed in space and time:
`illustrations come from 17 countries and 7 centuries, and, for that matter,
`3 planets and I star.
`
`Acknowledgments
`
`I am most thankful for access to these libraries: in London, The British
`Library, and British Patent Office Library. In Paris, Bibliotheque Na(cid:173)
`tionale, and Bibliotheque de l'Ecole Nationale des Ponts et Chaussees.
`In Tokyo, Arisugawa Memorial Park Library, and Japanese National
`Railroad Library. In the United States, the Library of Congress, New
`York Public Library at Lincoln Center, and, at Yale University, the
`Art and Architecture Library, Astronomy Library, Beinecke Rare
`Book and Manuscript Library, Center for British Art, Historical Med(cid:173)
`ical Library, Social Science Library, Sterling Memorial Library, and
`especially Interlibrary Loan.
`
`Original film separations for several maps and drawings were gener(cid:173)
`ously provided by Samuel Antupit ofHarry N. Abrams, Inc.; Gary
`Graham, IBM Corporation; David Monahan, Marine Cartography,
`Canadian Hydrographic Service; M. Roggli, Bundesamt fiir Landes(cid:173)
`topographie, Wabern, Switzerland; Paul A. Tukey, Bell Communi(cid:173)
`cations Research; Wild Leitz, Ltd., Heerbrugg, Switzerland; and the
`Statistics Bureau, Prime Minister's Office, Japan.
`
`0011
`
`

`
`II
`
`At Yale University, I am blessed with students who often listen
`sympathetically and then go on to make their own independent
`contributions. Three drawings here are adapted from student work.
`
`In this complex project, many have provided advice and assistance.
`I remember gratefully:
`
`For fmding (and selling) rare books and maps, Teresa Bridgeman,
`Jonathan Hill, Gordon Hollis, George N. Johnson, Jr., and Richard Lan.
`
`For their patient guidance in exploring Japanese information design,
`Akiko Hashimoto, Fumihiko Saito, and the essential Nagayo Sawa.
`
`For suggesting and contributing examples, Scott Adams, Robert
`Cameron, Inge Druckrey, Elisabeth Fairman, Gretchen Garner,
`Owen Gingerich, Howard I. Gralla, David H. Hathaway, Nicholas
`Johnson, Herbert A. Klein, Paul Levy, Pamela Pfeffer, Denise Scott
`Brown, Ani Stern, Vane Sutton-Vane, R. Gay Walker, Colin Ware,
`Jon Wertheimer, Berthold Wolpe.
`
`For reviewing the manuscript, Rudolf Arnheim, Samuel Edgerton, Jr.,
`Joanna Hitchcock, Virginia J. Tufte, and Kim Veltman; and for helpful
`advice, Robert K. Merton.
`
`For elegant book design and counsel for many years, Howard Gralla;
`for typesetting in Mono type Bembo, Michael and Winifred Bixler;
`for advice on an intricate printing job, Don Dehoff, William Glick, and
`Robert Hennessey; for vigilant production review, Carolyn Williams.
`
`For managing Graphics Press with special care, Elaine Lau and Kathy
`Orlando; and for managing the rest, Cynthia Bill.
`
`For superb and reflective research support, Scott Adams and
`Mark Hansen.
`
`For fme craft in artwork, and redrawing and adapting many of
`the examples, Nora Hillman Goeler.
`
`For her ideas and inspiration, Inge Druckrey.
`
`January 1990
`Cheshire, Connecticut
`
`0012
`
`

`
`1 Escaping Flatland
`
`EvEN though we navigate daily through a perceptual world of three
`spatial dimensions and reason occasionally about higher dimensional
`arenas with mathematical ease, the world portrayed on our informa(cid:173)
`tion displays is caught up in the two-dimensionality of the endless
`flatlands of paper and video screen. 1 All communication between the
`readers of an image and the makers of an image must now take place
`on a two-dimensional surface. Escaping this flatland is the essential task
`of envisioning information-for all the interesting worlds (physical, biological,
`imaginary, human) that we seek to understand are inevitably and happily
`multivariate in nature. Not flatlands.
`
`1 The idea of "flatland" is based on the
`classic by A. Square (Edwin A. Abbott],
`Flatland: A Romm1ce of Mmty Dimensions
`(London, 1884). A recent statement from
`an artist's viewpoint (How can modern
`painting, abstractionism, escape flatland?)
`is found in Frank Stella, Working Space
`(Cambridge, 1986).
`
`0013
`
`

`
`THis chapter outlines a variety of design strategies that sharpen
`the information resolution, the resolving power, of paper and video
`screen. In particular, these methods work to increase (r) the number
`of dimensions that can be represented on plane surfaces and (2) the
`data density (amount of information per unit area).
`
`IN this Japanese travel guide, an engaging hybrid of design technique,
`the abrupt shift from friendly perspective to hard flatland shows the
`loss suffered by giving in to the arbitrary data-compression of paper
`surfaces. A bird' s-eye view with detailed perspective describes local
`areas near the architecturally renowned Ise Shrine; then, on the right
`margin, a very flat map delineates the national railroad system linking
`the shrine to major cities, somewhat compensating for loss of a visual
`dimension with a broad overview. A change in design accommodates
`a change in the scale of the map, and local detail is shown in national
`context, a mixed landscape of refuge and overview. The horizontal
`layout combines harmoniously with the vertical orientation of the
`language, so that the stand-up labels point precisely to each location.
`
`13
`
`Guide for Visitors to Ise Shrine (Ise, Japan;
`no date; published between October 1948
`and April 1954, according to The Library,
`Ise Shrine, Mie Prefecture).
`
`0014
`
`

`
`I4 ENVISIONING INFORMATION
`
`When the toad (Bufo americanus LeConte) sheds its skin upon the
`occasion of a quarterly moulting, the suit leaves life's spaceland and
`collapses into flatland, not unlike our information displays.
`
`Mary C. Dickerson, The Frog Book: North
`American Toads and Frogs, with a Study if the
`Habits and Life Histories if those of the North(cid:173)
`eastern States (New York, 1906), pp. 74-75.
`
`2 John White, The Birth and Rebirth if Pic(cid:173)
`torial Space (London, 19 57); and Lawrence
`Wright, Perspective in Perspective (London,
`1983). See also the remarkable book by
`Kim Veltman, Linear Perspective and the
`Visual Dimensions of Science and Art: Studies
`on Leonardo da Vinci I (Miinchen, 1986).
`
`3 Redrawn from Emil v. Zmaczynski,
`"Periodic System of the Elements in a New
`Form," Journal of Chemical Education, 12
`(1935), 265-267; Frank Austin Gooch and
`Claude Frederic Walker, Outline ifitJorgatJic
`Chemistry, II (London, 1905), pp. 8-9; and
`Andreas von Antropoff, "Eine neue Form
`des periodischen Systems der Elemente,"
`Zeitschriftfiir A1zgewandte Chemie, 39 (1926),
`722-728; Edward Mazurs, Types of Graphic
`RepresentatiotJ of the Periodic System of Chem(cid:173)
`ical Elements (La Grange, Illinois, 1957).
`
`All sorts of techniques for doing better than flattened-out toad suits
`have evolved during some soo years of information design. 2 Since the
`I 5th-century Italian Renaissance, when Florentine architects perfected
`the necessary geometry, conventional perspective drawing has enriched
`representations of physical objects. And, for more abstract multivariate
`information not residing in our three-space reality, several enterprising
`methods have evolved-nearly silently, often to be found in workaday
`diagrams of those confronted with an overwhelming quantity of data.
`A few such teclmiques are well documented; for example, the elaborate
`structuring of the periodic table of chemical elements3 (with several
`
`(
`
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`

`
`hoodred arrangements proposed to capture the assorted complexities).
`Some recently perfected statistical graphics, self-consciously multi(cid:173)
`variate, enrich flatland with the dynamics of rotating point clouds on
`
`computer screens-a marvel, although navigation in three-dimensional
`scatterplots is not a trivial matter. 4 Another approach, here on the right,
`slices and projects data from many angles onto six of the twelve surfaces
`of a pentagonal dodecahedron (only six faces are needed, since opposite
`parallel faces show identical views).
`Nearly every escape from flatland demands extensive compromise,
`trading off one virtue against another; the literature consists of partial,
`arbitrary, and particularistic solutions; and neither clever idiosyncratic
`nor conventionally adopted designs solve the inherent general difficul(cid:173)
`ties of dimensional compression. Even our language, like our paper,
`often lacks immediate capacity to communicate a sense of dimensional
`complexity. Paul Klee wrote to this point:
`
`It is not easy to arrive at a conception of a whole which is constructed from
`parts belonging to different dimensions. And not only nature, but also art, her
`transformed image, is such a whole.
`
`It is difficult enough, oneself, to survey this whole, whether nature or art, but
`stillmore difficult to help another to such a comprehensive view.
`
`This is due to the consecutive nature of the only methods available to us for
`conveying a clear three-dimensional concept of an image in space, and results
`from deficiencies of a temporal nature in the spoken word.
`
`For, with such a medium of expression, we lack the means of discussing in
`its constituent parts, an linage which possesses simultaneously a number of
`dlinensions. 5
`
`And perspective projection is a simple extension of a two-surface,
`made unmistakable by everyday experience in three-space itself. Yet
`much of our data-and nature's pattern-have far greater complexity.
`What, then, are general strategies for extending the dimensional and
`informational reach of display flatlands? And what specific techniques
`effectively document and envision multivariate worlds? Why are some
`performances better than others?
`
`To begin, a series of splendid examples.
`
`ESCAPING FLATLAND
`
`15
`
`4 Andrew W. Donoho, David L. Donoho,
`Miriam Gasko, MAC SPIN Graphical Data
`Analysis Software (Austin, Texas, 198 5),
`illustration at p. 3 5 (redrawn); and the
`important 1974 paper by Mary Anne Fish(cid:173)
`erkeller, Jerome H. Friedman, and John W.
`Tukey, "PRIM-9: An Interactive Mul(cid:173)
`tidimensional Data Display and Analysis
`System," in WilliamS. Cleveland, ed., The
`Collected Worksof]olm W. Tukey, Volume V,
`Graphics: 196 5-198 5 (Paciftc Grove, California,
`1988), 308-327. For a report of some diffi(cid:173)
`culties, see Peter J. Huber, "Experiences
`with Three-Dimensional Scatterplots,"
`Journal of the American Statistical Association,
`82 (June 1987), 448-453.
`
`Showing the oft-plotted Anderson data
`for Iris setosa ·, Iris versicolor . , and Iris
`. , redrawn from Paul A. Tukey
`virginica
`and John W. Tukey, "Preparation; Pre(cid:173)
`chosen Sequences of Views," in V. Barnett,
`ed., Interpreting Multivariate Data (New
`York, 1981), pp. 205-206.
`
`5 Paul Klee, On Modem Art (London, 1948),
`p. 15, translated by Paul Findlay from Uber
`die moderne Kunst (Bern, 1945). Recent
`computer adventures seek to give dimen(cid:173)
`sionality and nonlinearity to text. See E. J.
`Conklin, "Hypertext: An Introduction and
`Survey," Computer (September 1987), 17-41.
`
`0016
`
`

`
`16 ENVISIONING INFORMATION
`
`c
`
`A
`
`B
`
`So all their angles there wyned toge(cid:173)
`ther,make a folide angle. And for the better fight thereof, I haue fet
`here afigure wherby ye lhall more eaft!y conceiue it, the bafe of the
`figure is a triangle,namely,A B C,if on euery fide of the triangle A B
`C,ye rayfe vp a triaogle,as vpon the fide A B,ye ra1fe vp the triangle
`A F B,and vpon the fide A C the triangle A F C, and vpon the fide B
`C,the triangle B F C,and fo bowing the triangles raifed vp,that their
`toppes,namely ,the poimes F meece and ioyne together in one point,
`ye thai eafily and plainly fee how thefe three fuperficiall angles A F B
`B F C,C F A,ioyne and clofe together, touching the one the other in
`the point F,and fo make a folide angle.
`
`DIRECT methods for the display of three dimensions include making
`models, as in this 1570 edition of Euclid's Elements, where little paper
`constructions teach solid geometry. Models pleasingly represent the
`smooth surfaces of three-space, as in architectural miniatures and math(cid:173)
`ematical solids; more obstreperous statistical data however, call for
`computer analysis of data point clouds.
`Narratives of the universe were impressively cranked up in orreries,
`simulations of our solar system (as known in I8oo), with planets and
`their satellites rotating and orbiting. Although a triumph of gear ratios,
`the machines did commit a grave sin of information design-Pridefully
`Obvious Presentation-by directing attention more toward miraculous
`contraptionary display than to planetary motion.
`
`Euclid, The Elements of Geometrie (London,
`I570), with preface by John Dee, English
`translation by Henry Billingsley, fol. 3 I4.
`A fme guide to various extra-dimensional
`elaborations in book design is Gay Walker,
`EccmtricBooks (New Haven: Yale Univer(cid:173)
`sity Library, I988).
`
`William Pearson, "Planetary Machines,"
`in Abraham Rees, ed., The Cyclopaedia; or,
`Universal Dictionary if Arts, Sciences, and
`Literature, Plates, Vol. IV (London, I82o),
`plate XI; and Henry C. King with John R.
`Millburn, Geared to the Stars: The Evolutio11
`of Planetariums, Orreries, a11d Astronomical
`Clocks (Toronto, I978).
`
`0017
`
`

`
`ESCAPING FLATLAND 17
`
`Color stereo pair of Bonaduz, Canton
`ofGrisons, Switzerland, October, I975,
`photographs taken with Wild Leitz aerial
`camera RCIO. Scale about r :rr,ooo.
`
`6 Stereoscopic viewers will assist in obtain-
`ing three-dimensional images. The effects
`can be seen without optical devices by some,
`however. The views here are arranged for
`the wide-eyed or pie-eyed method of viewing
`stereograms; those using the popular cross(cid:173)
`eyed method will see sunken mountains and
`raised rivers. See Thomas Avery and Graydon
`Berlin, Interpretation of Aerial Pliotograplis
`(Minneapolis, 4th edition, r985), pp. 25-90.
`
`Particularly intriguing are stereo illustrations, which deliver vivid
`three-dimensional scenes by means of paired images (one for each eye),
`which are then fused mentally by viewers. Aerial landscapes, molecular
`structures, and other worldly objects are commonly portrayed; repre(cid:173)
`sentations of more abstract and ragged quantitative data are rarely seen.
`. Many viewers must struggle (and some fail) to fuse the images; even
`experienced eyes may require several minutes of vacant staring before
`obtaining the splendid stereo view. 6 Recent work on computer visual(cid:173)
`izations, stereo images, holograms, and so on hint at an increasing depth
`and pace to analytic displays, perhaps eventually without all the para(cid:173)
`phernalia accompanying current methods. 7
`
`7 Promising results are D. B. Carr, W. L.
`Nicholson, R. J. Littlefield, and D. L. Hall,
`"Interactive Color Display Methods for
`Multivariate Data," and K. R. Gabriel and
`C. L. Odoroff, "Illustrations of Model Diag(cid:173)
`nosis by Means of Three-Dimensional Bi(cid:173)
`plots," inEdwardJ. Wegman and Douglas
`J. DePriest, Statistical Image Processilzg mzd
`Graphics (New York, rg86), 2r5-250, 258-
`274; Thomas V. Papathomas,James A.
`Schiavone, and Bela Julesz, "Stereo Ani(cid:173)
`mation for V cry Large Data Bases," Com(cid:173)
`puter Grap/iics mzd Applications (September,
`r987), rS-27; and WilliamS. Cleveland and
`Marylyn E. McGill, cds., Dynamic Graphics
`for Statistics (Belmont, California, rg88).
`
`0018
`
`

`
`8 George Sarton, "Early Observations of the
`Sunspots," Isis, 37 (May 1947), 69-71; for the
`full history, D.Justin Schove, ed., Sunspot
`Cycles (Stroudsberg, Pennsylvania, 1983).
`
`18 ENVISIONING INFORMATION
`
`SUNSPOTS were examined in detail by telescope in the early r6oos,
`after some 200 years of repeated viewing by unaided eyes in Athens,
`China, Japan, and Russia. It was difficult for Europeans to see sunspots
`at all because Aristotle had said that celestial bodies were perfect and
`without blemish, a fancy which became official church doctrine in the
`middle ages. 8 Then, in r6ro-r6r2, Galileo and others made detailed
`telescopic observations of sunspots.
`Galileo marked spots directly onto paper flatland, maintaining the
`proper image plane while drawing a large diagram of a spotted sun:
`
`The method is this: Direct the telescope upon the sun as if you were going to
`observe that body. Having focused and steadied it, expose a flat white sheet of
`paper about a foot from the concave lens; upon tins will fall a circular image
`of the sun's disk, with all spots that are on it arranged with exactly the same
`syrrunetry as in the sun. The more the paper is moved away from the tube, the
`larger tlus image will become, and the better the spots will be depicted. Thus
`they will all be seen without damage to the eye, even the smallest of them(cid:173)
`wluch, when observed through the telescope, can scarcely be perceived, and
`only with fatigue and injury to the eyes .
`
`..
`
`IS TO RIA
`E DIMOSTRAZIONI
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`E LORO ACC1DENTI
`COJ!PRE.SE IN 'fRE LETTERE SCR/TTE
`ALL'ILLVSTRISSIMO SIGNOR
`MARCO VELSER! LINCEO
`D V V M V 1 R 0 D' A V G V S T A
`CONSHiliH\0 Dl SVA MAtSTA CL$AUA
`DAL SIGNOR
`GALILEO GALILE! LINCEO
`
`N#i/ Fi:r(n/i,.,.,Fikfo/M M.mm111ir8 Prim.:rUJrl $(rtlfifi,
`D.COSIMO II. GJI.dN D>'CA DI10SCANA.
`Si 3Ui·~~n<:>MI fine k: Lcr!ttc, ~ DJ(qijifilicni d.d fin~o Ardle.
`
`In order to picture them accurately, I first describe on the paper a circle of the size
`that best suits me, and then by moving the paper towards or away from the tube
`I find the exact place where the image of the sun is enlarged to the measure of the
`circle I have drawn. This also serves me as a norm and rule for getting the plane of
`the paper right, so that it will not be tilted to the luminous cone of sunlight that
`emerges from the telescope. For if the paper is oblique, the section will be oval and
`not circular, and therefore will not perfectly fit the circumference drawn on the
`paper. By tilting the paper the proper position is easily found, and then with a pen
`one may mark out spots in their right sizes, shapes, and positions. But one must
`work dextrously, following the movement of the sun and frequently moving the
`telescope, which must be kept directly on the sun. 9
`
`MDCXIII.
`INROMA,
`CON LICBNZA DE SYPER.JO.R.l.
`
`9 Galileo Galilei, History and Demonstrations
`Concemi11g Sunspots a11d Their Phenomena
`(Rome, 1613), translated by Stillman Drake,
`Disco11eries a~~d Opiniom of Galileo (Garden
`City, New York, 1957), pp. II5-II6.
`
`0019
`
`

`
`ESCAPING FLATLAND
`
`I9
`
`21.od..h,
`
`•
`
`•K
`
`'" ~
`
`As more observations were collected daily, small multiple diagrams
`recorded the data indexed on time (a design simultaneously enhancing
`dimensionality and information density), with the labeled sunspots
`parading along alphabetically. This profoundly multivariate analysis(cid:173)
`showing sunspot location in two-space, time, labels, and shifting relative
`orientation of the sun in our sky-reflects data complexities that arise
`because a rotating sun is observed from a rotating and orbiting earth:
`
`Illustrations from Christopher Scheiner
`(writing under the pseudonym "Apelles"),
`De Maw/is Solari bus (Rome, 1613), pp. 14-
`15; and his Rosa Ursina sive Sol (Bracciani,
`1626-1630), p. 63. On the dispute between
`Galileo and Scheiner concerning sunspots,
`see William Shea, Galileo's Intellectual
`Revolution (New York, 1972), pp. 48-74.
`
`b
`
`a 0 ho1i'Z.9n,a b c, arcus Jolis diurnus. Soloriens ex pwfe a.,macula> exhibec ~uas vides,
`occiden> vero c, easdem. raf!o111: primi motiu, nomtihil muedz(.Et heme mafutinam veperfinamtj.
`mu!Monent, onvres maculw 1uoftdte jubeunf:.0iod JemeZ exhi&ijje ef nwnuiffe_, f1ficia£
`
`For some astronomers, particularly those seeking to reconcile data
`with doctrine, it was m1clear just where stmspots were located. Surely
`not on the surface of that perfect sphere; perhaps satellites orbited the
`sun, or even planets were in transit across the sun's face-speculations
`soon demolished by Galileo. Through an elegant chain of visual reason(cid:173)
`ing and with characteristic sardonic bhmtness, Galileo, writing from
`Florence in August r6r2, converts empirical observation into focused
`evidence supporting conclusions. His argument unfolds the raw data
`("what the eye of the forehead" registers) into a luminous explanation
`of mechanism ("what the eye of the mind" envisions), 10 a deeply visual
`logic that produced precise insights f:'lr beyond those achieved by others
`who had also observed sunspots in the early r6oos. Indeed, "it was more
`than 150 years before any important addition was made" 11 to Galileo's
`results, as reported in 1613:
`
`I therefore repeat and more positively confirm to Your Excellency that the dark
`spots seen in the solar disk by means of the telescope are not at all distant from its
`surface, but are either contiguous to it or separated by an interval so small as to be
`quite imperceptible. Nor are they stars or other permanent bodies, but some are
`
`1 0 The persistent relationship between
`artistic capacity for visualization and ex(cid:173)
`traordinary scientific achievement is de(cid:173)
`scribed in Robert Scott Root-Bernstein,
`''Visual Thinking: The Art of Imagining
`Reality," Transactions of the American Philo(cid:173)
`sophical Society, 75 (1985), 50-67. For further
`evidence about Galileo, see Erwin Panofsky,
`Galileo as a Critic of tlze Arts (The Hague,
`1954), p. 5: "An excellent draughtsman,
`Galileo loved and understood 'with perfect
`taste' all the 'arts subordinated to design' ...
`he was originally inclined to study painting
`rather than mathematics, and one of his
`most intimate and faithful friends was the
`outstanding painter of their native Florence,
`Ludovico Cigoli."
`
`11 R. J. Bray and R. E. Loughhead, Sunspots
`(London, 1964), p. 2. Galileo's analysis at(cid:173)
`tained special longevity because of its in(cid:173)
`sight and also the nearly complete absence
`of observable sunspots from 1645 until 1715 !
`Jolm A. Eddy, "The Maunder Minimum,"
`Science, I92 (June r8, 1976), rr89-1202.
`
`0020
`
`

`
`12 Galilee Galilei, History and Demonstrations
`Concerning Sunspots and Their Phenomena
`(Rome, 1613), translated by Stillman Drake,
`Discoveries and Opinions of Galileo (Garden
`City, New York, 1957), pp. ro6-107, II6-
`II 7. Galilee had been through all this once
`before when he first saw craters on the
`moon, another supposedly perfect celestial
`sphere. One of Galilee's opponents, "who
`admitted the surface of the moon looked
`rugged, maintained that it was actually
`quite smooth and spherical as Aristotle had
`said, reconciling the two ideas by saying
`that the moon was covered with a smooth
`transparent material through which moun(cid:173)
`tains and craters inside it could be discerned.
`Galilee, sarcastically applauding the ingenu(cid:173)
`ity of this contribution, offered to accept it
`gladly-provided that his opponent would
`do him the equal courtesy of allowing him
`then to assert that the moon was even more
`rugged than he had thought before, its sur(cid:173)
`face being covered with mountains and
`craters of this invisible substance ten times
`as high as any he had seen. At Pisa the
`leading philosopher had refused even to look
`through the telescope; when he died a few
`months afterward, Galilee expressed the
`hope that since he had neglected to look at
`the new celestial objects while on earth, he
`would now see them on his way to hea(cid:173)
`ven." Stillman Drake, "Introduction: Sec(cid:173)
`ond Part," Discoveries a~~d Opinions if Galileo
`(Garden City, New York, 1957), p. 73·
`
`20 ENVISIONING INFORMATION
`
`always being produced and others dissolved. They vary in duration from one or
`two days to thirty or forty. For the most part they are of most irregular shape, and
`their shapes continually change, some quickly and violently, others more slowly
`and moderately.
`
`They also vary in darkness, appearing sometimes to condense and sometimes to
`spread out and rarefy. In addition to changing shape, some of them divide into
`three or four, and often several unite into one; this happens less at the edge of the
`sun's disk than in its central parts. Besides all these disordered movements they
`have in common a general uniform motion across the face of the sun in parallel
`lines. From special characteristics of this motion one may learn that the sun is
`absolutely spherical, that it rotates from west to east around its own center, carries
`the spots along with it in parallel circles, and completes an entire revolution in
`about one lunar month. Also worth noting is the fact that the spots always fall
`in one zone of the solar body, lying between the two circles which bound the
`declinations of the planets-that is, they fall within 28° or 29° of the sun's equator.
`
`The different densities and degrees of darkness of the spots, their changes of shape,
`and their collecting and separating are evident directly to our sight, without any
`need of reasoning, as a glance at the diagrams which I am enclosing will show. But
`that the spots are contiguous to the sun and are carried around by its rotation can
`only be deduced and concluded by reasouing from certain particular events which
`our observations yield.
`
`First, to see twenty or thirty spots at a time move with one common movement is
`a strong reason for believing that each does not go wandering about by itself, in the
`manner of the planets going around the sun .... To begin with, the spots at their
`first appearance and final disappearance near the edges of the sun generally seem to
`have very little breadth, but to have the same length that they show in the central
`parts of the sun's disk. Those who understand what is meant by foreshorteuing on
`a spherical surface will see this to be a manifest argument that the sun is a globe,
`that the spots are close to its surface, and that as they are carried on that surface
`toward the center they will always grow in breadth while preserving the same
`length .... this maximum thinuing, it is clear, takes place at the point of greatest
`foreshortening ....
`
`I have since been much impressed by the courtesy of nature, which thousands of
`years ago arranged a means by which we might come to notice these spots, and
`through them to discover things of greater consequence. For without any instru(cid:173)
`ments, from any little hole through which sunlight passes, there emerges an image
`of the sun with its spots, and at a distance this becomes stamped upon any surface
`opposite the hole. It is true that these spots are not nearly as sharp as those seen
`through the telescope, but the majority of them may nevertheless be seen. If in
`church some day Your Excellency sees the light of the sun falling upon the pave(cid:173)
`ment at a distance from some broken window pane, you may catch this light upon
`a flat white sheet of paper, and there you will perceive the spots. I might add that
`nature has been so kind that for our instruction she has sometimes marked the sun
`with a spot so large and dark as to be seen merely by the naked eye, though the
`false and inveterate idea that the heavenly bodies are devoid of all mutation or al(cid:173)
`teration has made people believe that such a spot was the planet Mercury coming
`between us and the sun, to the disgrace of past astronomers. 12
`
`0021
`
`

`
`With continuing observation, indexing each image afresh grew
`cumbersome. Christopher Scheiner's Rosa Ursina sive Sol, completed
`in 1630, arrays the apparent path of spots across a stationary disk,
`
`Christopher Scheiner, Rosa Ur