When a fascinating chaos has been observed enough to reveal patterns that allow prediction, the human mind is ready to ask, “Why?” So it is with the cosmos. Tracing the answers to this question throughout history allows us to understand the development of cosmology and its effects on moral imagination.
Like most of the Quadrivium, Astronomy has lost its place in today’s classical liberal arts curriculum. In this talk, Dr. Seeley will give a brief introduction to Astronomy when it was a liberal art, and indicate how its developments remain a crucial part of the story of our civilization.
The historian Paul Johnson begins his work on the twentieth-century, Modern Times, in this surprising way.
The modern world began on 29 May 1919 when photographs of a solar eclipse, taken on the island of Principe off West Africa and at Sobral in Brazil, confirmed the truth of a new theory of the universe. It had been apparent for half a century that the Newtonian cosmology was in need of serious modification. It had stood for more than two hundred years. It was the framework within which the European Enlightenment, the Industrial Revolution, and the vast expansion of human knowledge, freedom and prosperity which characterized the nineteenth century, had taken place. . . . The public response to relativity was one of the principal formative influences on the course of twentieth-century history. It formed a knife, inadvertently wielded by its author, to help cut society adrift from its traditional moorings in the faith and morals of Judeo-Christian culture.
Johnson was referring to the dramatic confirmation of Einstein’s theory of relativity, which predicted that the light of stars would be bent by the gravitational field of the sun twice as much as was predicted by Newtonian theory. Johnson, a writer with a flair for the dramatic, made dramatic claims about the societal impact of two astronomers. Newton’s ideas about gravity provided a framework for the Enlightenment? The Industrial Revolution? The growth of democracy? How could that be? What use could knowledge of gravity be for a pre-space age society? My daughter says, “Gravity is my enemy.” There is nothing you can do about it. How could Einstein’s theories about the relativity of space and time, which only are detectable on a cosmological or atomic scale, contribute to undermining Judeo-Christian culture?
Johnson sees Newton and Einstein as examples of a more general truth: “Great scientific innovators . . . change our perception of the physical world and increase our mastery of it. But they also change our ideas. The second effect is often more radical than the first.” I think this is a fascinating claim in itself, and at this conference we want to encourage in ourselves a love of learning interesting things just for their own sake, apart from what use you might make of them in the classroom. But, if true, it also points out how today’s classical liberal arts curriculum, in which history so often plays the integrating role, should stretch itself to include an understanding of the scientific and mathematical developments which characterize ages and cultures.
What was so amazing about Newton anyway? An apple falls, and he’s a genius? Everyone has always known that things fall. As one of my students said about something, “It’s as obvious as gravity.” And yet it was revolutionary? To understand a revolution, you have to understand from what it revolted. In this case, that means going back to the ancient view of the cosmos, and the work of the 2nd century astronomer, Claudius Ptolemy. Ptolemy was to ancient astronomy what Euclid was to geometry. He gathered together and perfected all that the Greeks had learned about the sky that shone so brilliantly at night in the eons before cities and their lights erased it from ordinary experience. According to the internet, over 80% of the human race cannot see the stars. When the 1994 Northridge earthquake wiped out lights in Los Angeles, concerned citizens made 911 calls about strange lights in the sky.
I would never have really seen the night sky except for visiting my grandparents’ farm in Michigan. There I saw the Man in the Moon, the Big Dipper, and, my personal favorite, Orion (Tolkien’s Menelvagor, the Swordsman of the Sky). That was about all. Those who lived on the farm knew much more about the night sky; my aunt would point things out, but I had a hard time seeing them. It’s like staring at stuff under a microscope or looking at ultrasounds—it’s all just a blur to me, though the experienced eye sees everything distinctly.
Thankfully, my college’s commitment to liberal education demanded a serious encounter with the whole Quadrivium. At the beginning of Sophomore year, I spent two weeks systematically observing the sky with the naked eye, then studied Ptolemy, Copernicus, Kepler, Galileo, Newton, and Einstein over the next three years. Not only was I introduced to the historical developments of science, but I came to see the reasons why we believe that the Earth moves, and that all things are heavy. More than that, I was able to enter into Dante’s imaginative vision of the cosmos, and understand the ways in which St. Thomas used astronomy to help understand the science of theology.
The Ptolemaic portion, especially grounded in the two weeks of observations, made me a friend of the night skies for the rest of my life. The observations involved watching the sky at different times through the night, and watching it at the same time every night for awhile, noting especially what was rising and what was setting. It set up a habit of keeping track of the sky, which was natural in our rural campus setting. In a place like that, the first thing you notice is how beautiful and overwhelming the lights in the night sky are. Then, in the profusion of lights, you might notice some clumping of stars, some brighter, some less bright, and the Moon standing out in size, shape, and brightness. If you spend some time outside on a starry night, you should be able to see the Moon and stars move, slowly but perceptibly over an hour or so, from east to west, just like the Sun, covering the entire sky in the course of one night. All the stars stick together, moving as one, but the Moon, if you pay attention, shifts its position slowly, falling behind the stars noticeably. As you get to know the sky over many months, you might be struck by the way in which most of the stars never change their positions to one another, though they are always moving. Orion is the same, day and night, forever; his faithful dog, Sirius, remains always at his side. But they start their night journey at different places, higher in the sky with each passing day. One month, Orion is high in the Southern sky as the night opens up, another month, much further to the right and coming down, another month and he is low in the West, a few months later, he has disappeared altogether. But the Moon drifts the other way, falling behind more each night, and changing shape, too, getting larger as its sunset position gets lower in the East, until it rises beautifully full as the Sun sets in the West.
The Moon is a wanderer among the stars. And if you pay attention over months to some of those brighter stars, you might notice them wandering, too. Not Sirius, the dog-star, one of the brightest, but Venus and Jupiter and Mars the red. But though the Moon always drifts behind the star flow at the same steady pace, Venus falls back away from the setting sun for a while, then stalls about 45 degrees away, then slowly starts to catch up until it disappears. Coincidentally, soon a bright star appears in the early morning in the East, performing the same away-and-back-again motion. You might soon come to suspect that the Evening and Morning Stars are really the same planet (the Greek word for “wanderer”). Jupiter’s backward drift is not limited like Venus’s, but neither is it steady like the Moon’s. It will fall behind for awhile, then catch up a bit, then fall behind more, and catch up a little, and fall behind more.
These are some of the basic night sky movements that all civilizations seem to have come to know from the beginning: the never-varying nightly movement of the whole sky from East to West, the change of first evening positions of the constellations, the steady drift backward of the Moon, the cyclical back-and-forth drifting of the planets. Through devoted observations over centuries, they realized that, though the heavens are always in motion, their motions are absolutely predictable, and they can guide religion, agriculture, navigation.
When a fascinating chaos has been observed enough to reveal patterns that allow prediction, the human mind is ready to ask, “Why?” Ptolemy shared the common conviction of human beings watching the stars over millennia—the heavens are so different from the earth! They are always the same. Though the mountains may fall and the hills turn to dust, cities and empires come and go, Orion is always there, exactly the same for Ptolemy as for the first recorded observers. Like all the stars, he moves, but always in the same way, always with the same even, never-varying pace, always in conjunction with almost all the rest of the heavenly panoply. And though the planets wandered among the stars, observations revealed how tantalizingly predictable their wanderings were. So different from the movements of birds, or horses, or arrows, or volcanoes. According to thousands of years of human observations, the heavenly bodies were eternal, they always were, they always will be, world without end. They were immortal, divine, yet visible, and moving with what must be mathematical precision. The hope of drawing close to God by uncovering the mathematical elegance and precision of the divine heavens is what attracted Ptolemy to devote his life to studying the heavens.
Meditating that only the mathematical, if approached enquiringly, would give its practitioners certain and trustworthy knowledge with demonstration both arithmetic and geometric resulting from indisputable procedures, we were led to cultivate most particularly as far as lay in our power this theoretical discipline. And especially were we led to cultivate that discipline developed in respect to divine and heavenly things as being the only one concerned with the study of things which are always what they are.
Not only would this open the way to a knowledge of God Himself, but it would inspire the moral lives of its devotees:
And indeed this same discipline would more than any other prepare understanding persons with respect to nobleness of actions and character by means of the sameness, good order, due proportion, and simple directness contemplated in divine things, making its followers lovers of that divine beauty, and making habitual in them, and as it were natural, a like condition of the soul.
Ptolemy also believed that, if the heavens are divine and unchanging, they must be moving in divinely simple and unchanging ways, a view confirmed by the experience of watching the heavens revolve in a great spherical movement around the heavenly north/south axis, always at the same speed. The great task of the mathematical astronomer was to show how the wanderings of the Sun (also revealed to be a wanderer ), Moon, and planets could be based on the divinely simple movement on circles at uniform speed. Doing this satisfactorily, in a way that allowed perfect calculations of every appearance of every heavenly body throughout never-beginning and never-ending time involved a little theoretical complexity. Planets would have to rotate on circles which themselves rotated on circles, which were off-center compared to the spherical motion of the fixed stars, and the rotation itself would be around yet a third mathematical center. Complex, yes, but mathematically graspable, Ptolemy’s majestic vision of a heavens full of elegant, eternally dancing gods provided precise calculations that needed little adjustment for over a thousand years.
A central feature of Ptolemy’s cosmos was the Earth, small as a point compared to the great sphere of the stars, fixed motionless at the very center of the universe. Ptolemy did realize that it would have been mathematically simpler to assume that the Earth revolved while the stars were motionless, but all common sense rejected that. All earthy stuff just falls straight down and stops, showing no tendency to rotate at all. Even more, for the Earth’s rotation to account for the daily movement of sun and stars, it would have to be spinning at something like 1,000 miles an hour; for it to account for the annual motions it would have to be moving close to 30,000 miles an hour.
In the light of what happens around us in the air such a notion would seem altogether absurd. For let us grant them what is unnatural: the lightest and least dense bodies [the stars] do not move at all . . . while the densest and heaviest bodies execute their own swift and uniform motion. . . . They would then admit that of all the motions in the earthly region the swiftest is the rotation of the earth. In a short time it performs so vast a rotation. As a result, everything not attached to it would appear to be always moving in the direction opposite the earth’s. Not a cloud nor any other thing flying or thrown upward would ever be floating eastward. For the earth would always outstrip them all as it overtook them in its eastward motion. Consequently all other bodies would seem to be traveling westward as they were left behind.
To assume the Earth moves would be theoretically simpler, but it would violate all common sense. So why do we accept such an absurdity without question, to the point of even laughing patronizingly at the simplicity of such a master mathematician as Ptolemy? (Please take a moment to consider why you accept such an absurdity.)
Before pursuing this question, I would like to take a moment to consider the implications of Ptolemy’s views on ancient and medieval thought and society. First of all, to dispel a few myths. Every educated person in the Greco-Roman world knew that the Earth was round. Ptolemy summarized well-known evidence for that fact, then produced tables and tables that allowed collating observations taken from the different angles of different locations on the round globe. Secondly, believing that the Earth was at the center of the universe did not give the ancients a puffed up view of man. Quite the opposite. The earth and everything on it was mortal, corruptible, prone to failure and ugliness. The heavens were where it was at—always beautifully and divinely elegant, without change, without failure, without blemish of any kind. While poets like Homer and Virgil imagined the souls of men to descend hopelessly under the earth, philosophers like Plato and Cicero dared to hope that death would release them into the heavens. In the Dream of Scipio, Cicero imagined a Roman general being raised into the heavens, where his famous grandfather explains the cosmos to him:
Now the globes of the stars far surpass the magnitude of our earth, which at that distance appeared so exceedingly small, that I could not but be sensibly affected on seeing our whole empire no larger than if we touched the earth with a point. And as long as I continued to observe the earth with great attention, How long, I pray you, said Africanus, will your mind be fixed on that object; why don’t you rather take a view of the magnificent temples among which you have arrived? . . . Below this, if we except that gift of the gods, the soul, which has been given by the liberality of the gods to the human race, every thing is mortal, and tends to dissolution, but above the moon all is eternal.
The effect of the experience was to diminish his native Roman thirst for glory and fame while increasing his thirst to govern himself and his country according to the pattern of the Supreme Governor who orders the cosmos so beautifully.
Now, in order to encourage you, my dear Africanus, continued the shade of my ancestor, to defend the state with the greater cheerfulness, be assured that for all those who have in any way conduced to the preservation, defense, and enlargement of their native country, there is a certain place in heaven, where they shall enjoy an eternity of happiness. For nothing on earth is more agreeable to God, the Supreme Governor of the universe, than the assemblies and societies of men united together by laws, which are called States.
But the never-beginning, never-ending character of the heavens made it very difficult for any of them to conceive a final end to history. Just as all the night wanderers returned to their exact positions every 25, 800 years, all life and history will repeat, all will be born, die, rise, and then return.
Three things contribute to the overthrow of established cosmological theories—observational precision, theoretical simplicity and elegance, and a changing culture of receptivity. Copernicus offered theoretical simplicity, astronomers like Tycho Brahe and Galileo perfected observations, the revolutionary society of the Renaissance and early Enlightenment made a heliocentric theory desirable to many. New observations of novae and comets strongly suggested the heavens were not unchanging. Galileo showed that earthly motions could be understood mathematically. Johannes Kepler showed that Brahe’s observations of Mars would not fit regular, circular motion, but did perfectly fit an elliptical orbit, almost but not quite a circle. Kepler also showed that the planets changed speeds on their orbits, slowing down as they got further from the Sun. And he showed that the outer planets took longer to complete their orbits in a 3:2 ratio to their radii. Both Kepler and Galileo developed a new mathematics of infinitesimals in order to establish their theories.
But how did all these things fit together? Why did the heavens behave as Kepler discovered? Newton introduced a new approach to the study of the heavens, which involved a complete re-conceiving of nature and of God’s activity. If the heavenly bodies really are like those on earth, their motions should be explainable in the same way we explain motions here on earth. Galileo had developed a science of projectile motion, which allowed him to calculate precisely how far a mortar would shoot a cannon ball if a certain amount of force was used to shoot it off. Newton imagined that that kind of explanation was needed to explain not only the heavenly motions, but all motions.
If a leaden sphere is projected from the peak of some mountain with a given velocity along a horizontal line by the force of gunpowder, it may go on in a curved line for a distance of two miles, before it falls to earth : since here with the velocity doubled it may go on twice as far as it were, and with ten times the velocity ten times as far as it were. And by increasing the velocity it may be possible to increase the distance to any desired distance in which it is projected, and the curvature of the line that it may describe be lessened, thus so that it may fall only according to a distance of ten or thirty or ninety degrees ; or also so that it may encircle the whole earth or finally depart into the heavens, and from the departing speed to go on indefinitely.
And by the same account, by which the projectile may be turned by the force of heaviness in orbit and may be able to encircle the whole earth, also the moon is able, either by the force of heaviness, but only it shall be of heaviness, or some other force, by which it may be acted on, always to be drawn back from a rectilinear course towards the earth, and to be turning in its orbit : and without such a force the moon would not be able to be retained in its orbit.
Machine makers on earth use forces to cause motions. What if God were just a great machine maker, who set up nature like a great machine, dependent for its motions on a small number of forces? To understand nature, we would only need to figure out the forces that control it; without knowing those forces, all previous philosophers had speculated about the natural world in vain. (“Plato? Aristotle? Socrates? Morons!”)
Newton then began one of the greatest human undertakings ever. He decided that, before determining what forces were at work in nature, he needed to figure out all the infinite variety of forces God could use, and determine kinds of motion God could make with them. Once he had done that, he could look to see how the heavenly bodies behaved, then come to know what kinds of force God used to make them. For about a year and a half, Newton seems hardly to have left his rooms at Cambridge, completely absorbed as the universe revealed itself to him in ways never before conceived.
Newton the force-hunter had a fundamental principle. Bodies are just stuff, inert, unactive, so unactive that they don’t even slow themselves down once they get set in motion. A consequence of this is that any changes in direction or velocity mean a force must be at work (First Law of Motion). If a body gets hit by a force, it will immediately change its motion; the greater the change, the greater the force (Second Law of Motion). Measuring the change means measuring the force. So any time a body moves in a curve at varying speeds, some force must also be present, acting at every moment. (Newton had to invent calculus in order to determine the visible effects of infinitesimal changes.)
And this is where the apple comes in. Well, actually, a pendulum, like the old clocks. Having figured out at least some of the motions that can follow from any kind of force law, and realizing that elliptical orbits only follow from a force that grows stronger as the body moves closer (inverse square law), Newton looked closely at the Moon. He determined how curved its orbit was, then, in an amazing proposition, calculated exactly how fast the Moon would fall if Newton could bring it down to his study. (Newton lassos Moon!) He then compared it with how fast the weight on his pendulum fell, and found an exact match. The Moon was just a very big weight at a great height that behaves exactly like an apple or a man-made satellite would in the same position. The heavenly bodies are not heavenly at all. There is no such thing. Then, in an amazing master stroke, Newton used his knowledge of the inverse square law of force to weigh each of the planets and the Sun!
Newton’s work was the great triumph of the Enlightenment. The Renaissance had despised supposed medieval learning in favor of recapturing the ancient wisdom. The Enlightenment despised ancient learning, believing that mankind needed to start from scratch, ridding itself of the errors that infected all human culture, identifying the proper method to harness the power of human reason. Now, for the first time, man had real, certain knowledge about the physical universe. It did not come from philosophical reflection upon the essences of things, or reading old books, or relying in any way upon tradition. It came from the pure power of reason, asserting a small number of mechanical definitions and laws from which all possibilities could be discerned. It revealed that God had rationally chosen the laws to apply to the universe, and this mechanical God became a model for how humans should approach the now realizable goal of mastering all of nature. Nature itself held no unsolvable mysteries.
Newton’s cosmos formed the moral imaginations of generations; Tolstoy gives us a portrait of a life governed according to the cosmos in the character of Prince Nikolai Bolkonsky:
[Prince Nikolai] used to say that there were only two sources of human vice: idleness and superstition; and there were only two sources of virtue: activity and intelligence. . . . He himself was constantly occupied, now with writing his memoirs, now with higher mathematical calculations, now with turning snuff boxes on a lathe, now with working in the garden and supervising the construction work that never ceased on his estate. As the main condition for activity was order, so the order in his way of life was brought to utmost degree of precision.
Newton even spawned hope that human societies could be governed scientifically, if only one could determine the kinds of forces at work so as to direct them rationally. Confidence in Newtonian knowledge was so high that Immanuel Kant used it as a guiding principle in establishing his philosophy.
Similarly, the central laws of the motion of the celestial bodies supplied fixed certainty to that which Copernicus at first assumed only as a hypothesis, and at the same time gave proof of the invisible force binding together the system of the world (the Newtonian attraction), which would have forever remained undiscovered if [Copernicus] had not ventured, in a paradoxical but nonetheless correct manner, to seek the observed motions not in the objects in the heavens, but rather in the observer of those objects.
But, as foreshadowed in our opening quotation from Paul Johnson, this happy dream was not to last. Theoretical complexity and observational discrepancies eventually challenged Newton’s science. Mercury’s elliptical orbit drifted just slightly more in a century (43”) than predicted. By imagining space and time as interconnected and relative to observers, and gravity and matter as two sides of the same coin, Einstein successfully predicted the tiny amount of curvature around the sun. But he witnessed to Johnson’s claim: “The scientific genius impinges on humanity, for good or ill, far more than any statesman or warlord.”
Understanding the development of cosmology can help us to evaluate the proper effect of those scientific discoveries. And becoming a friend of the night sky might give us the consolation experienced by Sam in the very midst of Mordor:
There, peeping among the cloud-wrack above a dark tor high up in the mountains, Sam saw a white star twinkle for a while. The beauty of it smote his heart, as he looked up out of the forsaken land, and hope returned to him. For like a shaft, clear and cold, the thought pierced him that in the end the Shadow was only a small and passing thing: there was light and high beauty for ever beyond its reach. . . . Now, for a moment, his own fate, and even his master’s, ceased to trouble him. He crawled back into the brambles and laid himself by Frodo’s side, and putting away all fear he cast himself into a deep untroubled sleep.
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 “History of Street Lighting.”
 “Charts of the Night Sky.”
The featured image is “Lesson in Astronomy” by Giuseppe Angeli (1709-1798), courtesy of Wikimedia Commons.