The Believing Brain - Michael Shermer [160]
But in the past few days I returned to it and found it to be solitary, without its customary supporting stars, and as perfectly round and sharply bounded as Jupiter. Now what can be said of this strange metamorphosis?.… Was it indeed an illusion and a fraud with which the lenses of my telescope deceive me for so long—and not only me, but many others who have observed it with me?… I need not say anything definite upon so strange and unexpected an event; it is too recent, too unparalleled, and I am restrained by my own inadequacy and the fear of error.24
Nevertheless, Galileo concluded in the book that despite this new data his original theory about what he saw was correct. Why? The answer may be found in the visual presentation of the data.
The great scholar of the visual display of quantitative information Edward Tufte notes in his 2006 book, Beautiful Evidence, with the accompanying page from Galileo’s 1613 sunspot book (see figure 16), that “Galileo reported his discovery of Saturn’s unusual shape as 2 visual nouns that compare clear and murky telescopic views. In Galileo’s work Istoria e dimostrazioni intorno alle macchie solari (1613), words and images combine to become simply evidence rather than different modes of evidence.” The translation of the text in figure 16 accompanied by the two tiny drawings of Saturn reads: “The shape of Saturn is thus as shown by perfect vision and perfect instruments, but appears thus where perfection is lacking, the shape and distinction of the three stars being imperfectly seen.” Tufte describes this sentence as “one of the best analytical designs ever” because it represented “Saturn as evidence, image, drawing, graphic, word, noun.”25 Despite his more recent observations that the “three stars” had become “solitary” and “as perfectly round and sharply bounded as Jupiter,” Galileo’s image, drawing, graphic, word, and noun were congealed into evidence that his original observations were correct. Galileo never fully retreated from his first definitive conclusion.
Figure 16. Galileo’s Saturn as “Evidence, Image, Drawing, Graphic, Word, Noun”
The page from Galileo’s 1613 book on sunspots, in which he returns to the consideration of the Saturn enigma, concluding once again that he was right in the first place that Saturn was a three-bodied object. Source: GALILEO GALILEI, ISTORIA E DIMOSTRAZIONI INTORNO ALLE MACCHIE SOLARI (ROME, 1613), P. 25. AS REPRODUCED IN EDWARD TUFTE, BEAUTIFUL EVIDENCE (CHESHIRE, CONN.: GRAPHICS PRESS, 2006), P. 49.
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The solution to the Saturn problem is equally instructive of the data-theory dialogue in the narrative of belief. It wasn’t until 1659—half a century after Galileo’s observations—that Dutch astronomer Christiaan Huygens published the solution in his great work Systema Saturnium, one of the finest visual displays of both data and theory in the history of science. In figure 17 we see on display thirteen interpretations of Saturn produced by astronomers from 1610 (Galileo) to 1650 (Fontana and others), all wrong.
To our data-theory duo we should add presentation of the data and theory. In many ways, presentation is everything in understanding how beliefs are born, reinforced, and changed, because humans are so visually oriented as primates who once depended on three-dimensionality to navigate through dense arboreal environs. The data-theory-presentation triad is on exquisite display in figure 18, in which Huygens takes those two-dimensional Saturns, blows them up into 3-D, and puts them in motion around the sun. It is a marvelous presentation of both data and theory, incorporating Copernicus’s theory that the sun is at the center of the solar system instead of the earth (as in Ptolemaic cosmology), Kepler’s first law that planetary orbits are elliptical instead of circular (as in Aristotelian cosmology), and Kepler’s third law that the inner planets revolve around the sun faster than the outer planets.
Figure 17. Christiaan Huygens