by Adam Frank
A bell signal for the courts, a bell signal for the markets, a bell signal for the guilds—the use of bells to order urban life grew more confusing as cities became more complex. New trade and economic activity forced the institutional facts of European life to shift. Cities needed a simpler and more universal means of ordering temporal flow. In the midst of these shifting demands a radical new form of material engagement made its appearance. It was, without doubt, the most important invention of the last thousand years: the mechanical clock.
No one knows who invented the clock, though it was likely someone associated with a monastery.48 In particular, no one knows who invented its key component—the escapement, the notched metal rings that allow gravitational energy stored in a hanging weight to be regulated and regularly released. As an eighteenth-century writer commented, “It is certain that if we knew who first invented the means of measuring time by the movement of toothed wheels . . . this person would deserve all our praise.”49 No matter who came up with it, the invention quickly surged through the culture like a wave of possibility. Within a single century mechanical clocks would transform life in Europe.
The list of cities with public clocks begins with Orvieto, Italy, in 1307, followed by Modena in 1309, Parma in 1317, Ragusa in 1322, Milan in 1336 and Padua in 1344. By mid-century, mechanical clocks began to appear outside of Italy: Windsor Castle gained a clock in 1353, Avignon in 1353, Prague in 1354, Regensburg in 1358.50 By the beginning of the fifteenth century, public clocks had evolved into the standard even in smaller settlements. The town clock became a matter of both civic need and civic pride.
The mechanical regulation of time by machines freed cities from the cumbersome menagerie of bells and their various tolling patterns. Knowing the hour number was all that was needed for the new system. The establishment of twelve equally spaced hours for day and twelve equally spaced hours for night began in Italy and was applied unevenly throughout Europe. With the mechanical clock setting its rhythm, the regulation of time became abstracted, as did people’s relationship to time. Instead of a special set of bell signals to tell the armourers to start work, it was the bell tolling a numerical hour that initiated work (and pay).
FIGURE 3.4. Erfurt with clock. Europe builds a new experience of time as clocks set the pace of civic life. This manuscript illumination from Hartmann Schedel’s Weltchronik (1497) shows the city of Erfurt with a clock tower in the background. Such towers were a new addition to cityscapes and artists were keen to include them in their works.
The first clock towers were still bell towers; they had no clock faces. In these towers a clockworks drove the timing of the bells. By the beginning of the fifteenth century, however, the acoustic signal announcing the abstraction of evenly spaced hours had become visual with the introduction of clock dials. According to city records, in 1410 the keeper of the Horloge du Palais in Paris complained to the authorities about the extra burden of working with the complex machinery of the dial.51 And yet in these first clock faces only an hour hand appears. Smaller divisions of the day were not yet required.52
The hour itself, eventually imposed uniformly across Europe, was the medium of momentous change. “Abstract time became the new medium of existence”, wrote Lewis Mumford.53 By the end of the fifteenth century, the affairs of the urban world were fully regulated by clocks striking the hours. Communities became enslaved to the peal of clock bells and the march of the hour hand. “One ate, not upon feeling hungry, but when prompted by the clock; one slept, not when one was tired, but when the clock sanctioned it”, said Mumford. What began as the ordering of a prayerful life transformed into an ordering of life itself.
The human experience of time had been entirely redesigned by the invention and diffusion of the clock. The reawakening of learning, the growth of a wealthy new merchant class, the opening of new trade routes by ever more sophisticated seagoing vessels—each of these factors contributed to this newly imagined, clock-inspired form of lived time. As humans had done thousands of years before in the Neolithic and urban revolutions, time was reconstructed for our own imagined needs. And, as in those previous revolutions, the reformation of the universe in new cosmologies would have to follow.
THE REVOLUTION REVOLUTION: COPERNICUS MOVES THE HEAVENS
In 1497 Luca Pacioli, an Italian monk and mathematician, published the first description of double-entry accounting. A means of tracking both debits and credits, it would soon become the standard for Venice’s rapidly rising merchant class.54 In 1517 the firebrand theologian Martin Luther nailed his attack on the Vatican’s corruption—his Ninety-five Theses—to the door of Wittenberg’s church, effectively firing the first salvo of the Protestant Reformation.55 Two years later, five ships under Ferdinand Magellan’s direction set sail in what would become the first voyage to circumnavigate the planet.56 In the midst of these events, a young Polish lawyer and astronomer, Nicolaus Copernicus, was travelling through Italy and beginning work on a new vision of the heavens. There were many revolutions occurring at the beginning of the sixteenth century, and it would be Copernicus who gave them all a name.
Just as clock-driven time spread across Europe, a new power rose in the cities to make use of it. As the fifteenth and sixteenth centuries unfolded, the Catholic Church and its political allies faced a challenge from the rising merchant class. Wealth from seagoing trade (among other sources) allowed this newly empowered population to push against the century-old dictates of Europe’s social, political and intellectual structure. Renaissance ideals that individuals carried their own ability to parse the world rose alongside the Protestant Reformation’s rejection of papal hegemony.
As the Renaissance set its sights on a new order for man on Earth, the Protestant Reformation demanded a new order for man’s relation to God. Both movements were driven by material wealth and the new forms of material engagement they brought to a society rapidly gaining confidence in the ability to shape its own fate. Soon Earth itself would be moved to make way for the new era, and Copernicus would give the word revolution its revolutionary meaning.
FIGURE 3.5. Medieval representation of Ptolemy’s geocentric universe. Geocentrism, Aristotle’s physics and Catholic dogma were blended together during the late medieval period.
Born in Poland in 1473, Copernicus studied law, medicine and astronomy. By the time he reached his late thirties, he was already exploring alternatives to Ptolemy’s planetary model, which still prevailed after thirteen hundred years. He was sure that Ptolemy had put the sun in the wrong place, and that the sun—not the Earth—deserved the central position in the solar system. Though he still held firm to the Greek bias for uniform circular motion, he was offended by the sun’s subservient position as well as by the mathematical bells and whistles of Ptolemy’s geocentric model. Copernicus was sure that God, the author of the universe, had been more economical in his designs.
While simplicity may have motivated Copernicus to begin his work, the shift from a geocentric model of the cosmos to a heliocentric one required a heroic mathematical effort. He had set himself the task of reordering the solar system and, most important, developing a working mathematical model that could make accurate predictions about planetary motions.
Copernicus’ model had three critical features. The first and most obvious is that the sun was located at the centre of the planetary system. All planets, including Earth (he left the moon in orbit about the Earth), moved around the sun. The second critical feature of Copernicus’ model was the daily rotation of the Earth. Even by Copernicus’ era, the rotation of Earth remained a difficult idea for many scholars to swallow. The third and most important aspect of Copernicus’ model was its ability to cleanly recover the retrograde motion of planets, which had vexed astronomers for so long.
Copernicus’ explanation for the retrograde loops was the essence of simplicity compared with Ptolemy’s vision of epicycles. By assuming that the periods of planetary revolution increased with distance from the sun (Earth orbits more slowly than Venu
s, which orbits more slowly than Mercury, etc.), Copernicus turned all retrograde motion into a simple catch-and-pass effect. Faster-moving inner planets lap the outer ones. As an inner planet, such as the Earth, passes an outer one, such as Mars, the apparent motion of Mars—what an observer sees from the Earth’s surface—becomes a retrograde loop. The same effect occurs for observers looking from an outer planet towards an inner one. Thus for observers living in a heliocentric solar system, the mystery of retrograde loops reduces to nothing more than simple relative motion of planets against the fixed background of stars.
The geometrical manipulations Copernicus needed to illustrate this catch-and-pass effect were complex, but the underlying idea was much simpler than Ptolemy’s. And there was an added benefit to Copernicus’ system. In a geocentric model, the size and speed of each planet’s orbit was arbitrary. Bigger orbits with faster-moving planets worked just as well as smaller orbits with slower planets. Both configurations could fit the observations. The model had no built-in yardstick to gauge the dimensions of the heavens.
In the final versions of Copernicus’ heliocentric vision of the solar system (brought to fruition by Johannes Kepler), the timing of retrograde motions forced a single set of orbits. The observed retrograde periods allowed these new heliocentric models to translate time into space and set sizes and speeds for all the planetary orbits. Thus the model yielded an approximate size of the solar system based solely on its motions. When the calculations were completed it was clear that the new Copernican universe was much roomier than the Ptolemaic one.
The difference in size between the Ptolemaic and Copernican models was startling. The heliocentric cosmos was at least four hundred thousand times bigger (in terms of volume) than Ptolemy’s.57 This vast enlargement of the universe would be the first of many times that scientific astronomy would inflate the cosmos. With each step outward, humanity appeared to shrink in significance.
Copernicus’ book De revolutionibus orbium coelestium (On the Revolutions of the Celestial Spheres) was not published until just before his death in 1543.58 The work spread quickly throughout Europe thanks to a vibrant trade in manufactured (printed) books. Copernicus’ ideas were the essence of controversy. For some the new heliocentric model was heresy. For others, it did honour to the greater glory and conception of God. But in a changing world new cosmologies were dangerous. There was a background of political, theological and economic tumult that made debates over the Copernican universe flicker between metaphor and cosmic reality. Europe had been pushed off the centre of the map with the discovery of the New World. The Vatican was being pushed aside as the sole arbiter of both earthly and divine power. And the Earth had been pushed aside to make room for a new cosmic architecture.
FIGURE 3.6. Copernicus places the sun at the centre of the universe. The diagram on the left is from Copernicus’ De revolutionibus (1543). On the right is a figure from Galileo’s Dialogo (1632) after his telescopic studies showed moons orbiting Jupiter.
Ironically, even though they told completely different stories about the solar system’s architecture, Copernicus’ new model did not predict the motion of planets much better than Ptolemy’s. It is remarkable that the greatest scientific revolution in the history of humanity was driven, at first, more by aesthetics than by questions of data and predictions. Pythagoras and Plato would have perfectly understood the spirit of Copernicus’ effort. This emphasis on elegance and simplicity, dating back to the Greeks and revived in the Renaissance, would have a profound effect on the development of modern cosmology and physics. Today, scientists working the boundaries of both fields routinely invoke beauty, elegance and simplicity when considering rationales for choosing between competing theories.
The geometrical completion of Copernicus’ vision required one step beyond perfect circles, and that task fell to the quiet, mathematically oriented astronomer Johannes Kepler. Kepler was a kind of sixteenth-century Pythagorean who felt a rational mysticism in the workings of mathematics. Through his patient studies Kepler became convinced that a core of sublime and deeper mathematics must run through the foundations of the world’s structure. This conviction led the young Kepler to attempt modelling the Copernican solar system by nesting planetary orbits on the five Platonic solids. It was a glorious geometrical creation, and while it brought Kepler some fame, he soon realized its impossibility. Resolving to abandon the planetary prejudice for circular motion, Kepler spent the next ten years searching for the true geometry of orbits.59 Working with the exquisitely sensitive naked-eye observations provided by the Danish observer Tycho Brahe, Kepler found a different form—the ellipse—that could describe the motion of the heavens.
Ellipses, which appear as squashed circles, were a geometrical form known since the time of Pythagoras. But it was not until the sixteenth century that Kepler discovered that all planets travel through space on elliptical orbits as if guided by the hand of God the mathematician. It was cosmic order at its simplest. With the ellipse, Kepler was able to embrace all aspects of planetary motions—the variable speeds, the retrograde loops, the brightening and dimming of the planets—in an elegant heliocentric system expressed in the most compact mathematical expression. All of Kepler’s observations could be conveyed in just three simple laws, each based on elliptical orbits. The descriptive economy of these relations, which came to be called Keplers Laws, became a model for scientific descriptions of nature. The cosmos was sparse, elegant and built on an invisible superstructure of higher mathematics.
Material engagement would play a particularly explicit role in the final step of the Copernican revolution. Sometime around 1608, in a dusty workspace in the Dutch town of Middleburg, Hans Lippershey was hard at work grinding lenses for glasses. Trolling for treasures at his workbench, two of his children picked up different lenses and held them before their eyes. “Look,” one of them called out as he held two lenses apart and peered through them both. “The church steeple, it looks bigger!” The telescope had been discovered.60
News of the new optical device—the spyglass—spread rapidly among the scientific cognoscenti of Europe. A thousand miles to the south, an ambitious young mathematician and astronomer quickly taught himself how to shape glass lenses for his own use. Placing these lenses at the opposite ends of a ninety-centimetre tube, the young Galileo Galilei understood that he had found the key to his own future.
Galileo was born in 1564 into a highly cultured family in Pisa. His father was a well-known music theorist whose books on harmonies in musical scales had deeply affected Kepler’s thinking about the structure of the solar system. Galileo’s talent was obvious to his teachers and as a young man he climbed the academic ranks becoming one of the most famous astronomers in Europe.
Galileo’s genius was equal both in his scientific and his social ambitions. From an early age Galileo had set out to win fame for himself, and the telescope gave him the tool he needed. After building his own telescope in 1609, Galileo demonstrated its uses to the lords of Venice, who were so impressed with its capabilities they commissioned the young Galileo as a university professor and gave him a profitable trade in constructing telescopes for local merchants. These merchants and nobles understood immediately that bringing the far distance into view meant economic and military advantage. A thousand images of admirals, whalers and pirates standing tall on the foredeck, spyglasses raised, had been launched.
But Galileo was interested in astronomy, not conquest, and he began systematically observing the night sky with a series of ever more powerful instruments. In 1610 he published a short report of his work called Sidereus Nuncius or The Starry Messenger. The book caused a sensation, turning Galileo into a kind of Renaissance rock star. Proud and ambitious, Galileo was confident he could single-handedly win official Church acceptance for Copernicus’ theory.
He soon established a substantial body of evidence supporting the heliocentric universe and rejecting scholars’ slavish adherence to Aristotle. Galileo saw mountains on the moon and spots o
n the sun. Both observations contradicted Aristotle’s physics and cosmology, implying that celestial objects were just as imperfect and rutted as the terrestrial realm. Galileo watched Venus pass through a full round of phases, just like the moon, contradicting explicit predictions of the Ptolemaic model. Most shocking of all, Galileo discovered a family of satellites orbiting Jupiter. These “Galilean” moons of Jupiter offered proof that not everything orbited the Earth, shaking people’s confidence in the idea of a geocentric cosmos.
Galileo’s astronomical discoveries and his relentless arguments for the validity of the Copernican model made him a hero to many. With his newfound fame, he was certain the Catholic Church could be swayed from its adherence to Ptolemaic astronomy. But while he was a scientific genius, his political sense was clearly lacking. With a few infamous false steps Galileo found himself dragged before the Church’s most feared judicial body—the Inquisition—on charges of heresy.
Galileo’s trial was a turning point in the history of culture and science. The Church convicted him of failing to heed its orders by promulgating heliocentrism. Though the Church had won its battle by sentencing Galileo to house arrest, it was fated to eventually lose the cosmological war. Across Europe a new tide was rising. Astronomers, natural philosophers and scholars of all stripes were willing to put aside doctrine in order to use observation and experiment to guide their thinking.
