The Rise and Fall of Alexandria (17 page)

Though his own writings are lost, stories about his life and thoughts were widely reported in classical times, particularly his musings on astronomy. Diogenes Laertius devotes his first book in
The Lives and Opinions of Eminent Philosophers
to Thales:

 
Diogenes goes on to report that other people claimed that Thales did write two books, one on the solstice and the other on the equinox, thinking that everything else would easily be explained. Both Herodotus and Xenophanes are said to have praised him for being the first person able to predict the eclipses and motions of the sun and to have really studied astronomy—a slightly dubious claim, as the Chaldean Babylonian astronomers were considerably further advanced than the Greeks in charting the movements of the celestial bodies. Diogenes also attributes to Thales numerous other advances, all of which flowed out of his realization that the universe was rational and could be understood. He tells us that Thales affirmed the path (known as the ecliptic) along which the sun appears to move during the day, calculated the size of the sun, and was even the first person to call the last day of each month the “thirtieth,” presumably implying that he devised a new calendar. He also considered more intangible things, and we are told that

 
It was Thales’ method rather than his results that had begun a revolution, and he believed that with that method he could understand everything. Plato even credits him with being the first absentminded professor in history. He tells us that the philosopher would wander at night, gazing up at the stars and not looking where he was going. On one occasion this led him to fall into a ditch, where a pretty young girl found him and teased him, saying “that he was so eager to know what was going on in heaven, that he could not see what was before his feet,” before wryly adding, “This is applicable to all philosophers” (Plato,
Theaetetus,
174A).

The heir to Thales’ innovative view of the world was a man whose name stills strikes fear into the hearts of schoolchildren—Pythagoras. Like that of Thales, none of Pythagoras’s own work has survived. In fact, the cult which he led—half religious, half scientific—followed such a tight code of secrecy that it may well be that they forbade the writing of their secret formulas and discoveries. But even in his lifetime Pythagoras was such a towering figure that his biographical details were written down by others, and some of these accounts have survived.

Many busts of the great mathematician also survive, although none are contemporary, so they probably bear little relation to what he actually looked like. The only physical feature we do know about is a striking birthmark on his thigh. His father was a merchant from Tyre (in Syria) who was granted citizenship in Samos after he donated grain to the island in a time of famine. His mother was a native of Samos. Pythagoras grew up on the small island but also traveled extensively with his father, visiting Tyre, where he was taught by Chaldean magi from Babylonia, renowned for their knowledge of astronomy and astrology, and other learned Syrians. His educators also taught him to play the lyre and to recite Homer and other poetry.

It was on his travels, the sources tell us, that he encountered both Thales and his pupil Anaximander and attended the latter’s lectures on geometry and cosmology. It is also said that Thales advised the young man to travel to Egypt to study with the priests there, just as Thales himself had done fifty years previously.

Pythagoras took the old man’s advice. At that time Samos was allied to Egypt, which apparently gave Pythagoras access to the temples and their scholar-priests, who accepted him among them. There are so many close parallels between the society which Pythagoras later set up in Italy and the operation of the Egyptian priesthood that we can assume that it was in Egypt that he developed his ideas for his own school. This would explain his cult’s emphasis on secrecy, the striving for purity, and even the refusal to eat beans or wear any sort of animal skins, all of which were Egyptian priestly taboos.

Ten years after he arrived in Egypt, the country was invaded by Cambyses II, king of Persia, and Pythagoras was captured and sent to Babylon. There, we are told by the philosopher Iamblichus,

 
Around 530 BC or earlier Pythagoras left Babylon and made his way back to Samos, where he founded his school, which he called the Semicircle. There all manner of philosophical issues were discussed, his pupils sitting in a semicircle around the master. But back at his birthplace Pythagoras was again drawn into the political and diplomatic life of his people, which greatly distracted him from his philosophical work. It is also said that the local people disliked his Egyptian style of symbolic teaching, and he used this as an excuse to move the school to the Greek city-state of Croton (now Crotone) in present-day southern Italy. Here he reestablished the school with an inner circle known as the Mathematikoi who lived in the school, had no possessions, were vegetarians, and lived according to the strict regime prescribed by the master.

The members of the Semicircle were required to live by a set of tenets which stated that

 
Following the strictures of the group, Pythagoreans were hence the first to devise a consistent cosmos, based on pure numbers. By associating a point with 1, a line with 2, a surface with 3, and a solid with 4, they arrived at the sacred and omnipotent total number of 10. They believed that 10 would also be the key to understanding the structure of the cosmos.

A new element in this cosmic glass-bead game of mathematics and astronomy which Pythagoras introduced was music. Noting that vibrating strings produce harmonious tones when the ratios of their lengths are whole numbers, he went on to arrange the universe into similarly harmonic groups of spheres, even claiming that the Music of the Spheres really existed, though we have lost the ability to hear this background noise. According to Pliny, Pythagoras thought the musical interval between the earth and the moon was a tone, the moon to Mercury a semitone, Venus to the sun a minor third, Mars to Jupiter a semitone, and so on, so that the heavenly bodies actually played tunes as they waltzed past each other.

The Pythagoreans’ universe was one of absolute mathematical perfection. All heavenly bodies were, for them, perfectly spherical and moved in perfectly spherical orbits. At the center of the universe Pythagoras placed the earth, then the moon, then the sun, and next the planets. The whole universe was finally wrapped in an outer sphere of the fixed stars.

Arthur Koestler catches the essence of the structure perfectly: “The Pythagorean world resembles a cosmic musical box playing the same Bach prelude from eternity to eternity” (Arthur Koestler,
The Sleepwalkers,
p. 33).

Having turned the universe from a whim of the gods into a mathematical machine, Pythagoras set the stage for the objective study of astronomy. It was a pupil of Pythagoras, named Philolaus, who would first suggest that the reason for the rising and setting of the sun, moon, and stars might not be that these celestial bodies moved across the sky but that the earth itself was spinning. Sadly, he went on to obscure this brilliant and counterintuitive revelation by inventing two new astral bodies apparently invisible to the human eye. First he had the earth spinning around the “cosmic hearth,” an invisible fire at the center of the universe. On the same sphere there was another invisible object, a counterearth responsible for generating certain eclipses. The next sphere was our earth, then the moon, the sun, the five known planets, and finally the sphere carrying all the fixed stars, bringing the total number of celestial spheres up to the desired mystical number ten. Pythagoras would have been proud of him, had it not been such a cumbersome and fanciful creation!

The idea of a rotating earth would only be taken up again some centuries later, in Plato’s lifetime, by an astronomer named Heraclitus, who first proposed that the earth rotated once each day on its own axis. This mortally offended Plato, who still insisted that while the earth remained perfectly still at the center of the universe, every other celestial body rotated dutifully round it, and us. But this troubled Heraclitus. He had observed how some of the planets, in particular Venus, do not move smoothly through space as the perfect Pythagorean model insisted; rather, for some nights they advance, but then they stop and appear to go back on their own course for a few days. What, he asked, could make the planets wander so? It was a pressing problem, and one which even echoes into our language today, the word “planet” deriving from the Greek word for “wanderer.” For Heraclitus the solution was obvious: At least two of the planets, the so-called inner planets Venus and Mercury, must orbit around the sun, not the earth, and it was this complex movement that, viewed from the earth, seemed to make them wander. This astute model quickly caught on and became known as the “Egyptian System.” Its only flaw was that it didn’t go far enough—it still had the earth at the center of the universe, and the sun, now with its two “moons” of Venus and Mercury, obediently circling it.

This then was the confusing view of the universe that Aristarchus of Samos brought with him to Alexandria. But under her clear skies and aided by the new facilities of the museum’s observatory, that fog of confusion was about to lift, leading to one of the greatest scientific discoveries of all time.

Aristarchus had studied with Ptolemy II’s tutor, Strato of Lampsacus, a man whose devotion to the study of nature earned him the label “the Physicist.” Trained in Aristotle’s Lyceum in Athens, Strato took his master’s passion for the rational study of nature a step further by claiming that there was no need for any divine explanation of the universe. He declared that there was just nature, and that all things natural could be subjected to observation, measurement, and experimentation. In this respect he is considered the first atheist philosopher, but more important for our story, he essentially saw the universe as a mechanism which operated without the need for transcendental, divine forces. It was this idea that he impressed on the young Aristarchus, and which gave his pupil the confidence to ask a previously unasked question: If the universe is simply a machine, how does it work?

That we know the answer he devised in Alexandria is thanks only to a near fluke of history. Only one of Aristarchus’s works has come down to us, known as
On the Sizes and Distances of the Sun and Moon.
At first this seems disappointing, as it is largely assumed to be an early work, in which Aristarchus appears to accept the predominant, geocentric universe of those times. But on closer scrutiny even this early, fragmentary work is very revealing. First, the very notion that we can attempt to measure the size and relative positioning of the three largest-seeming celestial bodies—earth, sun, and moon—is a very bold opening gambit. It assumes that these are free-standing entities in stable relations with each other and of calculable dimensions.

It must be said that the figures he derived for the sizes of these bodies are wildly inaccurate. His own calculations led him to believe that the sun was about 20 times the size of the moon and 18 to 20 times as distant from the earth as the moon was. In fact the sun is about 450 times as far away from us as the moon is. He also calculated the diameter of the sun as about 7 times that of the earth, and therefore estimated that the sun’s volume was about 300 times the volume of the earth. In fact, the diameter of the sun is about 300 times that of the earth, its volume about 1.3 million times that of the earth. However, modern mathematicians have examined his propositions in great detail and find that effectively Aristarchus was not let down by his math (drawn from the ever-reliable Euclid) but by his observational data. So although Aristarchus was enormously wide of the mark, he hit the bull’s-eye in a far more crucial way. What he established, at least to his own satisfaction, was that the moon was the runt of the litter and that the sun was vastly bigger, more voluminous, and presumably heavier than the little earth. So why then should this huge celestial titan, at least 300 times the volume of the earth, be dutifully pirouetting around so small a planet every day? For the priests the answer had been simple: because that was how the gods had ordained it. But there were no gods in Aristarchus’s universe, so he had to seek answers elsewhere.