The New Lifetime Reading Plan

It was typical of Galileo to wonder what stars and planets might look like through a telescope; it was typical of him, too, that when he needed a telescope he made one himself. In 1609 he looked through his new instrument at the night sky, and was nearly bowled over by what he saw: the Milky Way, not a tenuous river of light stretching across the sky, but a con- tinuous band of an uncountable number of stars; the Moon pockmarked with craters and with craggy mountains and (it seemed) flat, tranquil seas; Venus, not a shining sphere, but a crescent like that of the moon, because, as Galileo quickly real- ized, it was in orbit around the sun; four small satellites circling around Jъpiter; strange knobby bulges on each side of Saturn (his telescope was not sharp enough to resolve the rings of Saturn). This was the sky as no one had ever seen it before.

Galileo rushed to spread the news of his observations, in a small book that he called Sidereus Nuncius (The Starry Messenger; there is a nice translation by Albert van Helden). Published in 1610, it was an instant bestseller, printed and reprinted ali over Europe; within five years it had even been translated into Chinese (by a Jesuit missionary). But while the world marveled, and savants rushed to acquire telescopes to see for themselves, Galileo began to ponder deeply the implications of his discoveries. He worked for twenty years to refine his opinions, and to present an unassail- able case for his cosmological theory.

What Galileo realized as a result of his astronomical obser­vations is that the view of the universe proposed by Copernicus in 1543 must be correct. Copernicus himself had not made that claim; he only said that to put the sun, rather than the Earth, in the center of the universe made for a simpler model, and made the mathematical calculations of orbital periods eas- ier. He also deflected any criticism of his motives by delaying publication of his work until he was on his deathbed; if the work proved controversial, he wouldn't have to deal with the consequences. Copernicus^ sun-centered model became widely known, but as long as it was considered "just a theory" it caused no particular controversy. People continued, on the whole, to believe in the old Aristotelian-Ptolemaic Earth-cen- tered universe, a model that had not only tradition and com- mon sense, but the sanction of the Church, behind it. In 1616 the Church authorities, sensing a threat, warned Galileo against teaching the Copernican system and issued an edict formally condemning it.

But Galileo was undeterred. Finally, in 1632, he published the work that rocked the foundations of classical learning and ensured his own place in the pantheon of scientific courage: The Dialogue Concerning the Two Chief World Systems. Using the dialogue form (familiar to Renaissance intellectuals through the rediscovered Greek classics, especially Plato [12]) for its persuasive power, he leads the reader step-by-step through his discoveries, and asking the reader to assent to innocuous-seeming conclusions on their basis. And then, at last, he says, "But notice that you yourself have now created the Copernical model.^,, It is a rhetorical work of genius, and is as persuasive today as it was in 1632. How, one wonders, could anyone fail to be convinced by it?

But the Church authorities at Rome were not persuaded; rhetoric had no power against dogma. And so Galileo was called before the Inquisition and forced to recant his theory; aging, tired, and ill, he really had no choice. He was required to spend the rest of his life under house arrest in his beloved city of Florence. But his Dialogue, though burned by the Inquisition, continued to circulate; within a few years, the Copernican model of the universe was taken as an established fact in schol- arly circles throughout Europe. And Galileo apparently knew that he would be vindicated; after he humbled himself before the Inquisition by affirming that the Earth lies unmoving at the center of the cosmos, he muttered under his breath, but loudly enough for witnesses to hear, "And yet—it does move."

Galileo^ work led directly to that of Sir Isaac Newton just a few decades later. But while Newton's Principia Mathematica was written for an audience of specialists and is quite impene- trable to the lay reader, Galileo was writing for the general edu­cated public. His Dialogue is a model of clarity; any serious reader can understand it. If you can find a copy, or can ask your library to get it on interlibrary loan, use Giorgio de Santillanas abridged-text version; he sharpens the dialogue by omitting some rhetorical byways, and his explanatory notes are excellent.

J.S.M.

THOMAS HOBBES

1588-1679 Leviathan