The Story of Western Science

by Susan Wise Bauer

Galileo retorted that the Dialogue was clearly hypothetical, and that he was neither holding nor defending heliocentrism—merely discussing it (which Bellarmine had explicitly allowed him to do). But the current head of the Inquisition, Cardinal Vincenzo Maculano, disagreed. In the spring of 1633, Galileo was forced to travel to Rome to defend himself. Maculano continued to be unimpressed by his arguments, and on April 28 he threatened the old man with “greater rigor of procedure” if he would not confess that he had broken Bellarmine’s strictures.

  Greater rigor of procedure: This was a code phrase for torture, and Galileo—now in his seventies and unwell—buckled. On June 22 he knelt in front of an assembly of churchmen and recited, obediently, “I abandon the false opinion which maintains that the Sun is the center and immovable.” With this confession in hand, Maculano sentenced Galileo to house arrest, ordered him to recite seven penitential psalms once a week for three years, and banned the Dialogue forever.14

  Under house arrest, Galileo went back to his studies on motion; in 1638 his work Two New Sciences, an exploration of non-Aristotelian physics, was printed in Leiden, where it did not have to receive the approval of a church censor. He died in 1642, his condemnation still active and the Dialogue still on the Index.

  But outside the reach of the Inquisition, the Dialogue continued to circulate: reprinted, read throughout Europe, translated into English in 1661. Barely a quarter century after Galileo’s death, the geocentric model was dead, and Aristotelian physics had been almost entirely superseded by new ways of thinking.

  To read relevant excerpts from Dialogue concerning the Two Chief World Systems, visit http://susanwisebauer.com/story-of-science.

  GALILEO GALILEI

  Dialogue concerning the Two Chief World Systems

  (1632)

  The best and most readable English translation is by Stillman Drake. Originally published in 1953, it is available in a nicely revised and annotated edition from the Modern Library Science Series.

  Galileo Galilei, Dialogue concerning the Two Chief World Systems, Ptolemaic and Copernican, trans. and with revised notes by Stillman Drake, Modern Library (paperback, 2001, ISBN 978-0375757662).

  * * *

  * A more detailed analysis of the relationship between Aristotelian philosophy and Christian theology is beyond the scope of this book. William C. Placher provides a useful summary in “The Fragile Synthesis,” Chapter 10 of A History of Christian Theology: An Introduction (John Knox Press, 1983).

  ELEVEN

  Instruments and Helps

  Improving the experimental method by distorting nature and extending the senses

  I am not a little pleased to find that you are resolved, on this

  occasion, to insist rather on Experiments than Syllogisms.

  —Robert Boyle, The Sceptical Chymist, 1661

  The next care to be taken, in respect of the Senses, is a

  supplying of their infirmities with Instruments, and, as it

  were, the adding of artificial Organs to the natural.

  —Robert Hooke, Micrographia, 1665

  In 1641, the year before Galileo’s death, the Irish teenager Robert Boyle set off on his “grand tour”—a trip through Europe in the company of his tutor, a rite of passage for well-to-do young men who had just finished secondary school (in Boyle’s case, Eton). By fall, the two travelers had reached the north of Italy and decided to winter in Florence. There, as Boyle’s early biographer Thomas Birch tells us, he

  spent much of his time in learning of his governor (who spake it perfectly) the Italian tongue, in which he quickly attained a native accent, and knowledge enough to understand both books and men. . . . The rest of his spare hours he spent in reading the modern history in Italian, and the new paradoxes of the great star-gazer Galileo, whose ingenious books . . . were confuted by a decree from Rome.1

  Confuted or not, Galileo’s works were clearly in wide circulation, and Robert Boyle found them entirely convincing: “This hypothesis of the earth’s motion,” he later wrote, “is far more agreeable to the phenomena, than the doctrine of Aristotle (who was plainly mistaken).”2

  By this point, Galileo’s telescopic observations from thirty years earlier had been duplicated, confirmed, and elaborated upon. Telescopes themselves had become stronger and better; the astronomer Johannes Kepler had theorized that two convex lenses would give a clearer, wider field of vision than the combination of convex and concave lenses used by Galileo, and in 1614 the German physicist Christoph Scheiner had built a Keplerian scope and proved the point (although the improved image was upside down). The same technology had been exercised in the opposite direction as well; Galileo himself had made a compound microscope, which he called an occhialino (“little spectacles”), and had used it to contemplate “an infinite number of small animals with enormous admiration.” (“The flea is very horrible,” he wrote to the Roman naturalist Federico Cesi in 1624.)3

  Seven years later, back from his tour and pursuing his own scientific research in London, Robert Boyle enthused over these new technologies. “With bold telescopes I survey the old and newly discovered stars and planets,” he wrote, “with excellent microscopes I discern, in otherwise invisible objects, the unimitable subtlety of nature’s curious workmanship . . . [and] by . . . the light of chymical furnaces, I study the book of nature.”4

  Chymical furnaces: This was a general term for vessels (porcelain flasks, pottery kilns, water or sand baths, brick or stone ovens) in which natural substances could be heated to artificial temperatures in order to find out more about their properties. Telescopes, microscopes, and furnaces were essentially unlike the instruments that Pythagoras and Archimedes and Aristotle had used in their investigations of the natural world. The ancients had measured nature, weighed it, calculated it, using their senses to comprehend the physical world. But scopes and furnaces changed the basic relationship between the senses and the subject. They distorted the natural world—magnifying it unnaturally, fusing or melting or distilling it (in Boyle’s own words, “torturing” natural bodies “into a confession of their constituent principles”).5

  This was part of the Baconian experimental program. “Neither the naked hand nor the understanding left to itself can effect much,” Bacon had written in the Novum organum. “It is by instruments and helps that the work is done.” Experiments done with these instruments and helps were “elaborate,” carried out in “elaboratories”—a word appearing in seventeenth-century English for the very first time.

  An elaboratory took time and money to construct, but Robert Boyle was independently wealthy and unencumbered by family, ideally situated to make use of the new instruments. He had, according to his acquaintance John Aubrey, a “noble laboratory and several servants (apprentices to him) to look to it. . . . He will not spare for cost to get any rare secret.”6

  Although he was better funded than most, Boyle was not the only young man experimenting with the new instruments and helps. In London he made the acquaintance of like-minded natural philosophers: “The cornerstones of the invisible, or (as they term themselves) the philosophical college, do now and then honour me with their company,” he wrote to a friend in 1646, “men of so capacious and searching spirits, that school-philosophy is but the lowest region of their knowledge.”7

  This “invisible college” was not, as later conspiracy theorists suggest, an occult or secret society. It was a loose network of amateur philosophers who met in shifting and overlapping circles to share their discoveries and discuss Baconian methods. The particular circle that young Boyle seems to have been most involved with was dominated by a Moravian theologian named John Amos Comenius, who was (oddly) both pro-Baconian and firmly anti-Copernican, since he felt that observation was essential to science, but also that the Bible was perfectly clear about the universe being geocentric.8

  By the early 1650s, Boyle’s skills in experimental science seem to have outstripped those of his London network, and he moved first to his family lands in Ireland and then
, searching for other like-minded philosophers, to Oxford. There he hired a poverty-stricken student named Robert Hooke to help him in his elaboratory.

  Together, the two men—Boyle now approaching thirty, Hooke barely into his twenties—worked to construct various devices that Boyle could use to “torture” nature into revealing its secrets. By 1658 they had succeeded in building an air pump, a notoriously complicated instrument that had first been publicly demonstrated by the German physicist Otto von Guericke in 1654. Guericke had used the air pump to suck all the air out of a hollow bronze ball formed from two separate hemispheres; he had then hooked the hemispheres to two eight-horse teams, which were unable to pull them apart. Guericke’s goal was to disprove a particular Aristotelian theory—that there was no such thing as “empty space” in the universe. Aristotle had argued that every place in the universe was occupied by something (a position later summed up as “Nature abhors a vacuum”). Guericke’s demonstration was meant to remove everything, even tiny invisible particles of air, from inside the ball in order to create a place where nothing existed—another mortal wound to Aristotelian physics.9

  Boyle’s own experiments with the air pump had a slightly different purpose. It was clear that nature did not abhor a vacuum; now he wanted to know what happened to various phenomena in the absence of air. Together, he and Hooke put all sorts of things into a chamber and pumped the air out: marbles, weights, feathers, a ringing watch alarm (they couldn’t hear it), gunpowder (hard to ignite), candles (they went out), a duck (it fainted), and several snakes (eventually, they died). The experiments led Boyle to his first publication, 1660’s New Experiments Physico-Mechanical: Touching the Weight of the Air and Its Effects. In it, he theorized that air particles can be understood as

  a heap of little bodies, lying one upon another, as may be resembled to a fleece of wool. For this . . . consists of many slender and flexible hairs; each of which may indeed, like a little spring, be easily bent or rolled up; but will also, like a spring, be still endeavouring to stretch itself out again.10

  Just as wool can be compressed within a closed fist into a more compact bundle, so also can air be pushed into a smaller area by external pressure. And, just as the wool expands again when the fist is unclenched, so also will air “spontaneously expand or display itself towards the recovery of its former, more loose and free condition” when the pressure is eased. This quality Boyle called the “spring of the air,” and he expressed it in a formula now known as Boyle’s Law: when gas is compressed into a smaller volume, its pressure increases.11

  The formulation of Boyle’s Law is generally seen as a milestone in the development of modern physics, but Robert Boyle was not primarily interested in physics. He was interested in the composition of air, because he was interested in the elements that made up the natural world: “His greatest delight,” John Aubrey observed, “is chymistry.”

  •

  Chymistry: in the seventeenth century, a realm occupied only by magicians and metalworkers.

  There was, in Boyle’s world, no field of endeavor called “chemistry.” Since ancient times, craftsmen had worked with precious metals and with dyes, which required some practical knowledge of chemical reactions. The Egyptians and the Greeks knew of fusion and filtration, crystallization and distillation. They knew how to use forges and furnaces to change the composition of their rough materials, and they were adept at using sulfur, arsenic, and mercury to change the colors of metals; arsenic, for example, turned copper white, “transforming” it (in the eyes of observers) into something completely different.12

  These techniques were known as chemia, a word borrowed from Egyptian by the Greeks. In the following centuries, Arab craftsmen further developed chemia (in Arabic, al-chemia), speculating, as they did so, on the nature of the transformations taking place. In the ninth century, at least two Arab thinkers (the Baghdad mystic Jabir ibn Hayyan and the Persian physician Abu Bakr Muhammad ibn Zakariyya al-Razi) suggested that, rather than being composed of the four traditional elements, metals were made up of the additional elements mercury and sulfur (an idea hinted at in Aristotle’s treatise Meteorology). In the thirteenth century, another Aristotelian, the Italian metallurgist Geber, suggested that matter was actually made up of something called corpuscles, rather than atoms. Atoms, by definition, could not be divided; but corpuscles could be penetrated by mercury, which mutated their internal structure into something else. If matter was made up of corpuscles, the transformation of some metals into others—copper into silver, or lead into gold—could actually take place.13

  This was a serious scientific theory, but the possibility that a worthless metal could be turned into gold opened up the practice of al-chemia to a host of tricksters and con men, who became adept at faking transformations and passing false “gold” off to gullible buyers. A partial rehabilitation of alchemy’s reputation came in the hands of the sixteenth-century German doctor Paracelsus, who was interested in alchemical techniques as a way of producing better medicines, and who argued that all natural changes (growth and development, fermentation and digestion) were essentially alchemical. But Paracelsus, who suggested that Aristotle’s four elements be replaced by three principles (the sulfur and mercury of the ninth-century alchemists, plus the additional principle of salt), was on the one hand a difficult, egomaniacal personality and, on the other, narrowly focused on alchemy’s uses for medical prescriptions; his theories made few inroads into the larger world of natural philosophy.

  Boyle believed that alchemy—the study of matter’s makeup—had as much to contribute to natural philosophy as did physics or astronomy. And the work he did in his elaboratory suggested to him that neither the Aristotelian theory of four elements nor the Paracelsian system of three principles held up under repeated experimentation. According to Aristotle, fire would always convert other elements into fire; why, Boyle asked, does nature so often “miss her end” in his chemical furnaces?

  The flame does never turn the bricks that it makes red-hot into fire; nor the crucibles, nor the cupels* nor yet the gold and silver that it thoroughly pervades. . . . And even when fire acts upon wood, there is but one part of it turned into fire, since, to say nothing of the soot and concreted smoke, the ashes remain fixed and incombustible.14

  As for Paracelsus’s three principles, Boyle doubted that sulfur could be considered a “primeval element,” since he had been able to produce a “sulphureous liquor” in his laboratory using, as ingredients, distilled liquids that were generally accepted by “chymists” as containing no sulfur at all.15

  In 1661, Boyle published his second major work, The Sceptical Chymist. It was constructed, very traditionally, as a dialogue among four characters: Themistius, a disciple of Aristotle; Philoponus, a Paracelsian; Carneades, Boyle’s mouthpiece for his own point of view; and Eleutherius, an interested bystander. Eleutherius asks well-informed questions; Themistius and Philoponus argue for the four-element and three-principle schemes, respectively; and Carneades demolishes them.

  But The Sceptical Chymist is entirely nontraditional in the proofs that Carneades offers. He does not argue (as Aristotle or Copernicus would have) on the basis of having come up with a better, more coherent answer. In fact, although Carneades suggests a different theory of matter (a version of Geber’s “corpuscles,” a “universal matter” that clumps together into masses that can be split, altered, and transformed), he is aware that he has no proof.

  But what he does have is a weight of repeated, elaborated experiments that disprove the Aristotelian and Paracelsian positions. Eleutherius, the intelligent layman, is delighted by this. “I am not a little pleased,” he says to Carneades, approvingly,

  that you are resolved on this occasion to insist rather on experiments than syllogisms. For I, and no doubt you, have long observed, that those dialectical subtleties that the schoolmen too often employ about physiological mysteries, are wont much more to declare the wit of him that uses them, than increase the knowledge or remove the doubts of s
ober lovers of truth.16

  It is not in syllogism—in coherent, unified systems—that truth will be found, but in repeated experimentation.

  Boyle refers to experimental proof nearly 150 times throughout the pages of The Sceptical Chymist. Furthermore, as he points out in the preface, these are experiments that have been performed in an elaboratory—not merely set up as thought problems. Boyle was continually exasperated by the habit, which many of his contemporaries had developed, of philosophizing about the material world on the basis of “chymical experiments, which questionless they never tried; for if they had, they would . . . have found them not to be true.” He was particularly irked by his contemporary Blaise Pascal’s Physical Treatises, which claimed to base its conclusions about the behaviors of liquids on experimentation, when in fact Pascal’s “trials” were merely “mental” experiments: “They require brass cylinders, or plugs,” Boyle complained, “made with an exactness that, though easily supposed by a mathematician, will scarce be found obtainable by a tradesman.” This was not good enough. Truths could not be discovered merely through the exercise of reason: “intricate and laborious experiments” had to be done. Which is why Boyle’s preface also warns the reader “not to be forward to believe chymical experiments . . . unless he that delivers them mentions his doing it upon his own particular knowledge.”17

  And even then, the experiments should be done again, and then repeated yet again. “Try those experiments very carefully and more than once, upon which you mean to build considerable superstructures either theoretical or practical,” Boyle later wrote to his readers, “and . . . think it unsafe to rely too much upon single experiments.” Variations in conditions, or materials, could drastically affect the outcome of an experiment. Only results that could be replicated over and over again should serve as the basis for a theory.18