Cosmos - Key Sections From Episode Seven - The Backbone of Night

The following are excerpts from Carl Sagan’s Cosmos - Episode 7 - “The Backbone of Night” At present, the full episode can be viewed at the link here.

”It Was Argued That The Universe Was Knowable”

Here, 25 centuries ago on the island of Samos, and in the other Greek colonies which had grown up in the busy Aegean Sea, there was a glorious awakening. Suddenly there were people who believed that everything was made of atoms, that human beings and other animals had evolved from simpler forms, that diseases were not caused by demons or the gods, that the earth was only a planet going around a sun, which was very far away. This revolution made cosmos out of chaos. Here in the sixth century BC, a new idea developed one of the great ideas of the human species. It was argued that the universe was knowable. Why? Because it was ordered; because there are regularities in nature which permitted secrets to be uncovered. Nature was not entirely unpredictable. There were rules which even she had to obey.

This ordered and admirable character of the universe was called cosmos, and it was set in stark contradiction to the idea of chaos. This was the first conflict at which we know between science and mysticism, between nature and the gods. But why here? Why in these remote islands and inlets of the Eastern Mediterranean? Why not in the great cities of India or Egypt, Babylon, China, or Mesoamerica? Because they were all at the center of old empires. They were set in their ways hostile to new ideas. But here in Ionia were a multitude of newly colonized islands and city states. Isolation, even if incomplete, promotes diversity, no single concentration of power could enforce conformity. Free inquiry became possible. They were beyond the frontiers of the empires. The merchants and tourists and sailors of Africa, Asia, and Europe met in the harbors of Ionia to exchange goods and stories and ideas. There was a vigorous and heady interaction of many traditions, prejudices, languages, and gods. These people were ready to experiment. Once you are open to questioning rituals and time honored practices, you find that one question leads to another.

What do you do when you’re faced with several different gods, each claiming the same territory? The Babylonian Marduk and the Greek Zeus were each considered king of the Gods master of the sky. You might decide since they otherwise had rather different attributes, that one of them was merely invented by the priests, but if one, why not both? And so it was here that the great idea arose, the realization that there might be a way to know the world without the God hypothesis. That there might be principles, forces, laws of nature through which the world might be understood without attributing the fall of every sparrow to the direct intervention of Zeus. This is the place where science was born. That’s why we’re here.

This great revolution happened between 600 and 400 BC. It was accomplished by the same practical and productive people who made the society function. Political power was in the hands of the merchants who promoted the technology on which their prosperity depended. The earliest pioneers of science were merchants and artisans and their children.

Thales

The first Ionian scientist was named Thales. He was born over there in the city of Miletus across this narrow strait. He had traveled in Egypt and was conversant with the knowledge of Babylon like the Babylonians. He believed that the world had once all been water to explain the dry land. The Babylonians added that their God Marduk had placed a mat on the face of the waters and piled dirt on top of it.

Thales had a similar view, but he left Marduk out. Yes, the world had once been mostly water, but it was a natural process which explained the dry land. Thales thought it was similar to the silting up he had observed at the delta of the River Nile. Whether Thales’ conclusions were right or wrong is not nearly as important as his approach. The world was not made by the gods, but instead was the result of material forces interacting in nature. Thales brought back from Babylon and Egypt, the seeds of new sciences, astronomy and geometry sciences, which would sprout and grow in the fertile soil of Ionia.

Anaximander

Anaximander of Miletus - over there - was a friend and colleague of Thales, one of the first people that we know of to have actually done an experiment. By examining the moving shadow cast by a vertical stick, he determined accurately the length of the year and the length of the seasons. For ages, men had used sticks to club and spear each other, and Anaximander used a stick to measure time.

In 540 BC or thereabouts on this island of Samos, there came to power, a tyrant named Polycrates. He seems to have started as a caterer and then went on to international piracy. His route was unloaded on this very breakwater, but he oppressed his own people. He made war on his neighbors. He quite rightly feared invasion. So Polycrates surrounded his capital city with an impressive wall whose remains stand to this day to carry water from a distance spring through the fortifications. He ordered this great tunnel, built a kilometer long; it pierces a mountain. Two cuttings were dug from either side, which met almost perfectly in the middle. The project took some 15 years to complete. It is a token of the civil engineering of its day and an indication of the extraordinary practical capability of the Ionians.

Theodorus

The enduring legacy of the Ionians is the tools and techniques they developed, which remain the basis of modern technology. This was the time of Theodorus, the master engineer of the age, a man who is credited with the invention of the key, the ruler, the carpenter, square, the level, the lathe, bronze casting. Why are there no monuments to this man? Those who dreamt and speculated and deduced about the laws of nature talked to the engineers and the technologists. They were often the same people. The practical and the theoretical were one. This new hybrid of abstract thought and everyday experience blossomed into science. When these practical men turned their attention to the natural world, they began to uncover hidden wonders and breathtaking possibilities. Anaximander studied the profusion of living things and saw their interrelationships. He concluded that life had originated in water and mud and then colonized the dry land. Human beings, he said, must have evolved from simpler forms. This insight had to wait 24 centuries until its truth was demonstrated by Charles Darwin.

Empedocles

Nothing was excluded from the investigations of these first scientists. Even the air became the subject of close examination by a Greek from Sicily named Empedocles. He made an astonishing discovery with a household implement that people had used for centuries. This is the so-called water thief. It’s a brazen sphere with a neck and a hole at the top, and instead of little holes at the bottom, it was used as a kitchen ladle. You fill it by immersing it in water. If after it’s been in there a little bit, you pull it out with the neck uncovered, then the water trickles out the little holes making a small shower. Instead, if you pull it out with a neck covered, the water is retained.

Now try to fill it with the neck. Covered with my thumb. Nothing happens. Why not? There’s something in the way. Some material is blocking the access of the water into the sphere. I can’t see any such material. What could it be? Empedocles identified it as air. What else could it be? A thing you can’t see can exert pressure; can frustrate my wish to fill this vessel with water if I were dumb enough to leave my thumb on the neck. Empedocles had discovered the invisible air he thought must be matter in a form so finely divided that it couldn’t be seen.

Democritus

This hint, this whiff of the existence of atoms was carried much further by a contemporary named Democritus. Of all the ancient scientists, it is he who speaks most clearly to us across the centuries. The few surviving fragments of his scientific writings reveal a mind of the highest, logical and intuitive powers. He believed that a large number of other worlds wander through space, that worlds are born and die, that some are rich in living creatures and others are dry and barren. He was the first to understand that the Milky Way is an aggregate of the light of innumerable faint stars beyond campfires in the sky, beyond the milk of Hera, beyond the backbone of night, the mind of Democritus soared.

He saw deep connections between the heavens and the earth. Man, he said, is a microcosm, a little cosmos. Democritus came from the Ionian town of Abdera on the northern, Aegean shore. In those days, Abdera was the butt of jokes. If around the year 400 BC in the equivalent of a little outdoor restaurant like this, you told a story about someone from Abdera, you are guaranteed a laugh. It was in a way the Brooklyn of its time.

For Democritus, all of life was to be enjoyed and understood. In fact, for him, understanding and enjoyment were pretty much the same thing. He said, “A life without festivity is a long road without an inn.” Democritus may have come from Abdera, but he was no dummy. Democritus understood that the complex forms, changes and motions of the material world all derived from the interaction of very simple moving parts. He called these parts atoms. All material objects are collections of atoms intricately assembled. Even we. When I cut this apple, the knife must be passing through empty spaces between the atoms. Democritus argued if there were no such empty spaces, no void, then the knife would encounter some impenetrable atom and the apple wouldn’t be cut. Let’s compare the cross sections of the two pieces. Are the exposed areas exactly equal? No said Democritus. The curvature of the apple forces this slice to be slightly shorter than the rest of the apple. If they were equally tall, then we’d have cylinder and not an apple. No matter how sharp the knife, these two pieces have unequal cross sections. But why? Because on the scale of the very small, matter exhibits some irreducible roughness and this fine scale of roughness. Democritus of Abdera identified with the world of the atoms. His arguments are not those we use today, but they’re elegant and subtle and derived from everyday experience, and his conclusions were fundamentally right.

Democritus believed that nothing happens at random, that everything has a material cause. He said, I would rather understand one cause than be king of Persia. He believed that poverty in a democracy was far better than wealth in a tyranny. He believed that the prevailing religions of his time were evil and that neither souls nor immortal gods existed. There is no evidence that Democritus was persecuted for his beliefs, but then again, he came from Abdera.

Anaxagorus

However, in his time, the brief tradition of tolerance for unconventional views was beginning to erode. For instance, the prevailing belief was that the moon and the sun were gods. Another contemporary of Democritus named Anaxagoras taught that the moon was a place made of ordinary matter and that the sun was a red hot stone far away in the sky. For this Anaxagoras was condemned, convicted, and imprisoned for impiety, a religious crime. People began to be persecuted for their ideas. A portrait of Democritus is now on the Greek hundred drachma note, but his ideas were suppressed and his influence on history made minor. The mystics were beginning to win.

Pythagorus

You see, Ionia was also the home of another quite different intellectual tradition. Its founder was Pythagoras, who lived here on Samos in the sixth century BC. According to local legend, this cave was once his abode, maybe that was once his living room. Many centuries later, this small Greek orthodox shrine was erected on his front porch. There is a continuity of tradition from Pythagoras to Christianity. Pythagoras seems to have been the first person in the history of the world to decide that the earth was a sphere. Perhaps he argued by analogy with the moon or the sun. Maybe he noticed the curved shadow of the earth on the moon during a lunar eclipse. Or maybe he recognized that when ships leave Samos their mast disappear last. Pythagoras believed that a mathematical harmony underlies all of nature. The modern tradition of mathematical argument essential in all of science owes much to him, and the notion that the heavenly bodies move to a kind of music of the spheres was also derived from Pythagoras. It was he who first used the word cosmos to mean a well-ordered and harmonious universe, a world amenable to human understanding.

For this great idea we are indebted to Pythagoras, but there were deep ironies and contradictions in his thoughts. Many of the Ionians believed that the underlying harmony and unity of the universe was accessible through observation and experiment, the method which dominates science today. However Pythagoras had a very different method. He believed that the laws of nature could be deduced by pure thought. He and his followers were not basically experimentalists, they were mathematicians, and they were thorough-going mystics. They were fascinated by these five regular solids, bodies whose faces are all polygons, triangles, squares or pentagons. There can be an infinite number of polygons, but only five regular solids.

Four of the solids were associated with earth, fire, air, and water. The cube, for example, represented earth. These four elements they thought make up terrestrial matter. So the fifth solid they mystically associated with the cosmos. Perhaps it was the substance of the heavens. This fifth solid was called the dodecahedron. Its faces are pentagons, twelve of them. Knowledge of the dodecahedron was considered too dangerous for the public. Ordinary people were to be kept ignorant of the dodecahedron. In love with whole numbers, the Pythagoreans believed that all things could be derived from them, certainly all other numbers. So a crisis in doctrine occurred when they discovered that the square root of two was irrational. That is, the square root of two could not be represented as the ratio of two whole numbers no matter how big they were. Irrational originally meant only that you can express a number as a ratio. But for the Pythagoreans, it came to mean something else, something threatening, a hint that their worldview might not make sense, the other meaning of irrational. Instead of wanting everyone to share and know of their discoveries, the Pythagoreans suppressed the square root of two and the dodecahedron. The outside world was not to know.

The Pythagoreans had discovered in the mathematical underpinnings of nature one of the two most powerful scientific tools. The other, of course, is experiment. But instead of using their insight to advance the collective voyage of human discovery, they made of it little more than the hocus pocus of a mystery cult. Science and mathematics were to be removed from the hands of the merchants and the artisans.

Plato

This tendency found its most effective advocate in a follower of Pythagoras named Plato. He preferred the perfection of these mathematical abstractions to the imperfections of everyday life. He believed that ideas were far more real than the natural world. He advised the astronomers not to waste their time observing the stars and planets. It was better, he believed, just to think about them. Plato expressed hostility to observation and experiment. He taught contempt for the real world and disdain for the practical application of scientific knowledge.

Plato’s followers succeeded in extinguishing the light of science and experiment that had been kindled by Democritus and the other Ionians. Plato’s unease with the world as revealed by our senses was to dominate and stifle Western philosophy. Even as late as 1600, Johannes Kepler was still struggling to interpret the structure of the cosmos in terms of Pythagorean solids and Platonic perfection. Ironically, it was Kepler who helped reestablish the old Ionian method of testing ideas against observations.

Why Did Science Lose It’s Way?

But why had science lost its way in the first place? What appeal could these teachings of Pythagoras and Plato have had for their contemporaries? They provided, I believe, an intellectually respectable justification for a corrupt social order.

The mercantile tradition which had led to Ionian science also led to a slave economy. You could get richer if you owned a lot of slaves. Athens in the time of Plato and Aristotle had a vast slave population. All of that brave Athenian talk about democracy applied only to a privileged few. Plato and Aristotle were comfortable in a slave society. They offered justifications for oppression. They served tyrants. They taught the alienation of the body from the mind - a natural enough idea, I suppose, in a slave society. They separated thought from matter. They divorced the earth from the heavens divisions, which were to dominate Western thinking. For more than twenty centuries, the Pythagoreans had won. In the recognition by Pythagoras and Plato that the cosmos is knowable, that there is a mathematical underpinning to nature, they greatly advanced the cause of science. But in the suppression of disquieting facts, the sense that science should be kept for a small elite, the distaste for experiment, the embrace of mysticism, the easy acceptance of slave societies, their influence has significantly set back the human endeavor.

The Adoption Of Platonism By Christianity

The books of the Ionian scientists are entirely lost. Their views were suppressed, ridiculed, and forgotten by the Platonists and by the Christians who adopted much of the philosophy of Plato. Finally, after a long mystical sleep in which the tools of scientific inquiry lay moldering, the Ionian approach was rediscovered. The western world reawakened experiment, and open inquiry slowly became respectable once again. Forgotten books and fragments were read once more. Leonardo and Copernicus and Columbus were inspired by the Ionian tradition.

A Tainted Earth At The Center of The Universe?

The Pythagoreans and their successors held the peculiar notion that the earth was tainted, somehow nasty, while the heavens were pristine and divine. So the fundamental idea that the earth is a planet that we’re citizens of the universe was rejected and forgotten. This idea was first argued by Aristarchus, born here on Samos. Three centuries after Pythagoras, he held that the earth moves around the sun. He correctly located our place in the solar system for his trouble. He was accused of heresy. From the size of the Earth’s shadow on the moon during a lunar eclipse, he deduced that the sun had to be much, much larger than the earth, and also very far away from this. He may have argued that it was absurd for so large an object as the sun to be going around so small an object as the earth. So he put the sun rather than the earth at the center of the solar system, and he had the earth and the other planets going around the sun.

He also had the earth rotating on its axis once a day. These are ideas that we ordinarily associate with the name Copernicus, but Copernicus seems to have gotten at least some hint of these ideas by reading about Aristarchus. In fact, in the manuscript of Copernicus’s book, he referred to Aristarchus, but it in the final version, he suppressed the citation. Resistance to Aristarchus, a kind of geocentrism in everyday life is with us still. We still talk about the sun rising and the sun setting. It’s 2200 years since Aristarchus, and the language still pretends that the earth does not turn, that the sun is not at the center of the solar system.

Aristarchus understood the basic scheme of the solar system, but not its scale. He knew that the planets move in concentric orbits about the sun, and he probably knew their order out to Saturn, but he was much too modest in his estimates of how far apart the planets are. In order to calculate the true scale of the solar system, you need a telescope. It wasn’t until the 17th century that astronomers were able to get even a rough estimate of the distance to the sun. And once you knew the distance to the sun, what about the stars?

How far away are they? There is a way to measure the distance to the stars and the Ionians were fully capable of discovering it. Aristarchus had toyed with the daring idea that the stars were distant suns. Now, if a star were as near as the sun, it should appear as big and as bright as the sun. Everyone knows that the farther away an object is the smaller it seems. This inverse proportionality between apparent size and distance is the basis of perspective in art and photography. So the further away we are from the sun, the smaller and dimmer it appears. How far from the sun would we have to be for it to appear as small and dim as a star. Or equivalently, how small a piece of sun would be as bright as a star? An experiment to answer this question was first performed in 17th century Holland by Christiaan Huygens, and is very much in the Ionian tradition.

Huygens drilled a number of holes in a brass plate and held the plate up to the sun. He asked himself which hole seemed as bright as he remembered the bright star Sirius to have been the previous evening. Well, the hole that matched was effectively one 28,000th, the apparent size of the sun. So Sirius, he reasoned must be 28,000 times further away than the sun, or about half a light-year away. It’s hard to remember just how bright a star is hours after you’ve looked at it, but Huygens remembered very well. In fact, if he had known that Sirius was intrinsically brighter than the sun, he would’ve gotten the answer exactly right. Sirius is 8.8 light years away from us. Between Aristarchus and Huygens, people had answered that question which had so excited me as a young boy growing up in Brooklyn. The question, what are the stars? And the answer is that the stars are mighty suns light-years away, in the depths of interstellar space.