The Starry Messenger
Galileo: Watcher of the Skies
by David Wootton
Yale University Press
by J.L. Heilbron
Oxford University Press; 514 pp.
I didn't make it to the First Annual Catholic Conference on Geocentrism, held in South Bend, Indiana on the November 6 weekend. I was interested, and badgered some editors to expense the trip, but no one thought it worth their funds. Nor have I read the 1,048-page, two-volume book Galileo Was Wrong: The Church Was Right by R. A. Sungenis and R. J. Bennett, published in 2007. ("Your world will be rocked," promises the promotional material, somewhat missing the point of geocentrism.)
If you do any science writing you get on the mailing lists for this kind of thing. It's amazing how many people see it as their life's mission to disabuse us of some scientific theory or other. Creationists, who dispute the foundations of modern biology, are only the best-known of these dissenters. Publish a science book or write a few articles and you will soon find your mailbox clogged with letters and pamphlets clamoring to set you straight on the real truth about the natural world and the sinister conspiracies that seek to keep us deluded.
Though neither a geocentrist nor a creationist, I confess to a sneaking sympathy for these contrarians. I fancy that in some small way they help to keep science honest. What, after all, do we know? Outside the narrow realm of what the philosopher J. L. Austin called "medium-sized dry goods" — the kinds of phenomena whose size and duration are on the scales our senses evolved to cope with — we are in a counterintuitive wonderland of curved spacetime and wave-particle duality. Real knowledge of that wonderland is awfully hard to extract. Copernicus's book De revolutionibus, which argued for a moving Earth and a stationary Sun, was published in 1543, yet the strongest objection to his system — the absence of stellar parallax — was not resolved until 1838. That's nearly 300 years to clear up one key point in a theory.
The most famous of early Copernicans, after Copernicus himself of course, is Galileo Galilei. His book Sidereus nuncius (The Starry Messenger), the first to describe systematic observations of the heavens by telescope, was published in 1610. By way of marking the quatercentenary of this event, the university presses of both Oxford and Yale have brought out new biographies of the astronomer by two distinguished historians of science. Curiously, the OUP's author is an American while Yale's is an Englishman. Both, however, are diligent scholars and credentialed experts in their field, fully acquainted with the source materials for Galileo's life and work. Even though neither book, nor indeed both put together, matches the length of Galileo Was Wrong, they offer masses of well-informed detail about their subject and his works.
That subject is a difficult one. As well as being a person and a scientist, Galileo has also been a token in the conflict between science and religion. The key event here is his formal abjuration of Copernicanism in June of 1633 under pressure from the Inquisition. Partisans of the Catholic Church, along with some philosophical relativists like Paul Feyerabend, have portrayed Galileo as a testy crank dogmatically committed to an unproven theory. Their case is not without merit: Galileo did have a cross-grained personality, and Copernicanism was short on supporting evidence. Galileo's attempt in his 1632 book Dialogue on the Two Main World Systems to supply the missing evidence with his preposterous explanation of the tides — he attributed them to a kind of rhythmic sloshing caused by the earth's movement — fortifies the anti-Galileo case.
The more common point of view tells the Galileo story as one skirmish in a Manichean conflict between Renaissance and Counter-Reformation, a war in which brave free-thinking empiricists struggled to escape a decaying, suffocating mass of religious dogmatism and obscurantism. There is something here, too. The Roman Church was a power center: a locus of order in a very disorderly world, but all too prone to the arrogance, corruption, and ideological rigidity attendant on political power everywhere.
Both these authors go much deeper than these partisan caricatures. The intellectual landscape of early seventeenth-century Italy was, they show, exceedingly complex. Church intellectuals of Galileo's time were conducting an orderly retreat from the astronomy of Ptolemy and Aristotle, with Tycho Brahe's quasi-heliocentric system as a popular fall-back position. (It had the earth stationary and all other planets revolving round the sun, which revolved round the earth. This, by the way, is the system favored by today's geocentrists.)
Astronomical systems of all sorts were in any case seen by the Church as mathematical, not physical; as handy algorithms for computing the positions of objects in the sky, not as descriptions or explanations of observed reality. It was made clear to Galileo that if he clove to this "save the appearances" approach, his Copernicanism would be acceptable. He could not do so, though, being too convinced of heliocentrism as physical fact.
Both these books are professorial, in the sense of assuming more familiarity with the subject matter than a nonspecialist reader is likely to have. Heilbron redeems himself somewhat with a useful glossary of names and a Galilei family tree. His book has some very fine color plates, too. (Though both books should have included a simple map of northern Italy. If you don't have the relevant locations and distances clear in your mind, you'll want an atlas handy.) Heilbron's book is also the more straightforward narrative, proceeding directly from birth to death with a few supplementary pages on the fortunes of Galileo's reputation.
David Wootton's book is comparatively meditative and moves around more freely in time. It is structured on a four-part framework: each section devoted to a particular part of Galileo's life and afterlife — i.e., his reputation — but with many forward and backward references. Its defects, for me, were a whiff of cod-Freudianism ("Galileo's internal conflict over the nature of knowledge is best understood as an ever deferred settling of accounts with his father") and poor math. I read Wootton's explanation of accelerated motion three times and still came away thinking he believes speed proportional to the square of time elapsed. No: it is distance traversed, not speed, that is proportional to t 2.
The main point of fact on which the authors differ is the vexed question of how good an empiricist Galileo was. The difference of opinion is not great, though. Neither author is at the extreme of skepticism represented by the great historian of science Alexandre Koyré (floruit 1950s), who thought Galileo's empiricism consisted mostly of thought experiments.
Wootton is the more skeptical of the two, making a case that Galileo was a "reluctant" empiricist, especially in his earlier years. Of Galileo's unfinished 1590 study of dynamics, Wootton says that "the limited role assigned to experiment in On Motion … is the role that would have been assigned to it by any orthodox Aristotelian." This remark has more force if you know how blithely un-empirical Aristotle's physics was. It taught, for example, that a hurled object moves in a straight line for a while then drops vertically, and that ice is heavier than water.
Heilbron is more inclined to give Galileo the benefit of the doubt as an experimenter — and there is considerable doubt — though even he concedes what is plainly the case, that "Galileo could stick to an attractive theory in the face of overwhelming experimental refutation." Perhaps Galileo was by temperament less a scientist than a mathematician? If so, he was a very incurious one. He seems to have taken no interest in algebra, for example, a great mathematical growth point in his time, coming to full flower with Descartes' Géométrie (1637). Nor did he pay any attention to Kepler's 1609 book Astronomia nova, which contained the mathematical key to planetary motion.
My impression of these biographies is rather the one I get from well-nigh any reading on the history of science: that no other style of thinking comes less naturally to human beings than the empirical and that Galileo was all too human in this regard. Neither of the authors thinks that Galileo's 1633 abjuration was sincere; nor does either credit the tale about Galileo muttering e pur si muove — "and yet it [the earth] does move" — as he rose from his knees at the end of the proceedings. He had, both agree, been a convinced Copernican since 1597, his thirty-fourth year.
On the matter of Galileo's religious beliefs our two biographers take different approaches. Wootton gives over a whole chapter to the topic, arriving at a "very strong presumption that Galileo was not a Christian." He was not, however, an atheist or agnostic in the modern sense, more a Platonic deist, seeing God "as the Supreme Mathematician."
Heilbron shows less interest in Galileo's inner life. He portrays Galileo's occasional religious observances in cynical terms. Of the Venetian ambassador's noting in 1610 that Galileo "frequently takes the sacraments and is very much changed from what he was," Heilbron observes drily: "The probable etiology of this increased observance will soon be clear." (Galileo was planning to woo the Jesuits prior to publishing his Copernicanism.)
Galileo's 1610 book Sidereus nuncius appeared just a few months after Kepler's Astronomia nova, in which the notion of elliptical planetary orbits was first offered. Both books stand almost precisely midway in time between Copernicus's De revolutionibus (1543) and Newton's Principia (1687), the latter of which gives a sound mathematical explanation of why orbits are elliptical.
This 144-year period, with Galileo's book at its center point, saw the first great dethronement of humanity — the first clear evidence that an assumption carried forward from our most primitive paleolithic condition down to the seventeenth century, the assumption that all things were created for the sake of man, is false. Two centuries after Newton came the second terrible blow with the publication of Darwin's On the Origin of Species.
We are still reeling. While acceptance of heliocentrism is now essentially universal outside the meeting rooms of the Hilton Garden Inn at South Bend, Indiana, still only 40 percent of Americans believe in evolution. The idea of our utter insignificance — a smart ape dwelling on an inconsequential planet — is more than most of us can bear. "We do not doubt," wrote Descartes, in the year of Galileo's death, "but that many things exist, or formerly existed and have now ceased to be, which were never seen or known by man, and were never of use to him." It was the work of the troublesome Florentine that first forced this deeply unwelcome fact on our attention. Here in two fine scholarly books are the man and the work all laid out for inspection.