The Rise and Fall of Alexandria (33 page)

 
Such was the gag order pinned on Galileo for daring to suggest that Aristarchus (plagiarized by Copernicus) was right and Claudius Ptolemy, after Aristotle, was wrong.

Claudius Ptolemy should not be criticized out of his time, however. The
Almagest
—a working, functioning model of the universe, creating mathematically based explanations for all the celestial movements as well as updating and expanding Hipparchus’s star catalog into four figures—was still a stupendous achievement. It may not have been a correct model, but it fitted the observations of the day and provided a usable, working cosmological background to the whole of the Middle Ages.

Nor was Ptolemy about to leave the cosmos at that. His follow-up work, the
Tetrabiblos
(“The Four Books”), is concerned with the impact which the heavens have upon individual personalities and worldly affairs—that is, astrology. The very mention of the word incites passionate controversy. It did so then, too. But whether we believe in it or not, Ptolemy’s
Tetrabiblos,
containing as it does a great deal of data drawn from Babylonian, ancient Egyptian, and earlier Greek sources, is
the
seminal work on the subject. The
Tetrabiblos
has had the longest life of all his works, being studied and employed by contemporary astrologers more than 1,800 years after he set down his basic principles.

As astrology, long dismissed as a pseudoscience by many, raises such passionate hackles, it is perhaps worth making some general observations on the subject before going into the details of Ptolemy’s formulations. Astrology as we know it probably originated largely in Babylonia, where priestly watchmen studied the movements of the heavenly bodies in great detail and over very long periods of time. Their reputations as magi were widespread and attracted the attention of classical thinkers like Pythagoras.

This was of course an age of omens, when kings and slaves alike attempted to deal with the often cruel vagaries of life by looking for clues as to what the future might hold. The magi believed that in their observations of the movements of the stars they had found a unique method to do just that—to assess the personalities and fates of individuals by considering the positions of the heavenly bodies at the moment of birth or what is called today “natal astrology.” Whether or not this connection is true or false, the least we can say about astrology is that it is humanity’s first enormous attempt at human psychology. From their observatories every possible form of human personality trait was projected onto the cosmos, though of course the astrologers argued the other way around. So Mars projected warlike characteristics onto people born under its influence, love emanated from Venus, and so forth. And here of course lies the problem: The scientific skeptic simply has to ask the question, how do the planets and other celestial bodies transmit these qualities to individuals on earth? Over the millennia this matter of transmission has essentially been an article of faith, a mystery whose veracity is borne out only by the accuracy of its predictions.

Ptolemy’s approach to astrology was that it was a conjectural rather than a precise science. So many variable factors had to be taken into account, such as race, country, and local culture, that absolute precision was difficult to achieve. And Ptolemy was also very aware that the subject was plagued by charlatans:

 
While Ptolemy displays no interest in the magical or mystical, or even the symbolic, aspects of astrology, he does draw on contemporary scientific thinking, which maintained that planetary characteristics were drawn from this relationship to the sun, where they received heat and light, and the earth, which was the source of moisture. Thus the moon was moist and dark, while Saturn, at the outermost position of all the known planets, was both cold and dark, and therefore thoroughly malevolent, the purveyor of death and destruction. His view was that the constantly changing positions of the celestial bodies created a continually fluctuating atmosphere to which all living creatures must respond.

Whether Claudius Ptolemy was right or not concerning astrology—and we should bear in mind that millions of people worldwide consult astrologers every day, as do countless millions of Western newspaper readers—it is his incredibly convincing presentation of the subject which gave his work its longevity. This is how he opens the
Tetrabiblos:

 
With the thirteen books of the
Almagest
and the four books of the
Tetrabiblos
Ptolemy effectively created a model of the universe and its workings which would dominate the world for more than a thousand years. Even though we may now consider his work flawed, the fact remains that by all the standards of the time, Ptolemy’s universe worked. And though for the most part his language remains couched in the scientific terminology of his day, he is not above occasionally letting us know his inner, spiritual attitude. For while his work was the first attempt to gather and systematize the mechanism by which the universe operates, his universe is not simply mechanical. Occasionally in his writing we can feel the inspiration behind his work, the sense of wonder that every astronomer knows and which must first have overwhelmed him when, as a child, he looked up through the clear Alexandrian night sky at the great vault of the heavens above him: “I know that I am mortal and ephemeral, but when I scan the multitudinous circling spirals of the stars, no longer do I touch earth with my feet, but sit with Zeus himself, and take my fill of the ambrosial food of the gods” (Claudius Ptolemy, quoted in W. Gunnyon,
A Century of Translations from the Greek Anthology,
epigram 33).

When Ptolemy looked back down to earth, however, he saw another challenge. Having completed his mammoth task on the heavens, he felt, like Socrates before him, it was time to bring his philosophy from the heavens down to earth.

That earth began for Ptolemy with Alexandria itself. Here in the markets were people from all over the earth, and piled in the warehouses along the waterfront were exotic goods gathered from as far as any traveler had ever reached. It was in part as a response to this cosmopolitanism that Ptolemy decided that the traders and explorers venturing out from this crossroads of the civilized world, which the Greek orator Dio Chrysostom called “the conjunction of the whole world,” needed a new guidebook: a book that would take them to the very edges of the known world, and perhaps beyond.

Ptolemy’s
Geography
is composed of eight books. Its intention was simple: to make and draw an account—an atlas—of the entire known world, and to construct maps which accurately reflected the texts. But as always, before proceeding to the work in hand it was necessary to review all the existing sources on the subject, evaluate their relative accuracy, and to devise and develop the necessary mathematical techniques for both the written geography and the accompanying cartography.

The idea of measuring the world (agreed by then to be spherical in shape) by dividing it into vertical and horizontal lines had been used by Eratosthenes when he made his astonishingly accurate measurement of the earth’s circumference, but it was Ptolemy who developed this idea into the notions of longitude and latitude, divided into degrees and minutes. With this framework established, the next question was how to make the most accurate assessment of the positions of the major cities, rivers, lakes, and mountains of the known world. Ptolemy realized that as winds vary, so the speeds of ships fluctuate; further variations are caused by the effects of tides and currents, so simply logging times traveled at estimated speeds would not necessarily produce accurate positioning. Similarly, travelers proceeding on foot or horseback rarely traveled in a straight line or at a constant speed. He preferred Eratosthenes’ method, measuring the angle of the sun’s shadow at midday to estimate where a traveler might be longitudinally. This data he chose to combine with all the known reports from mariners, traders, travelers, and explorers, to come up with a list of more than eight thousand localities, each uniquely pinpointed by its own longitude and latitude.

His next problem was that of projecting the spherical world (of which he knew that only about half was known) onto a two-dimensional piece of paper, to produce a map. In book 1 of the
Geography
he shows us precisely how he planned to do it, dividing the hemisphere of the known world into eighteen “meridians” of 10 degrees each, the longitudinal lines converging on the North Pole, and at their widest at the equator. The remaining task was therefore to transfer the eight thousand plotted locations onto the grid-planned page and fill in the details of the map.

Ptolemy’s
Geography
was lost from the fall of Alexandria until about AD 1300. When a copy of the great work was found it was in Arabic, and the world map, the twenty-six regional maps, and the sixty-seven maps of smaller areas were all missing. But the text was so detailed and comprehensive in explaining how to make the projections onto paper that enthusiastic cartographers found the maps relatively easy to reproduce. What then did they see as they put his world atlas together?

The first thing they must have noted was its sheer extent. Stretching from Iceland to China, it really did cover all of the Old World. Admittedly there were several oddities—much of India was not there, replaced by an enormous version of Sri Lanka named “Taprobana,” and Africa below “Ethiopa” appeared to go on indefinitely, as did China as the easternmost point on the map. But most of Europe, North Africa, and the Near and Middle East were much as we see them today. Egypt and the Nile; the details of the Red Sea and Arabia; the Aegean Islands; Cyprus; the leg, high-heeled boot, and football of Italy and Sicily; the square box of the Iberian Peninsula; and France, Germany, and Denmark were easily identified. The British Isles grew an interesting extension jutting out from eastern Scotland, but the southwestern limb of the Cornish Peninsula was there, as were Wales, the Isle of Man, and a plausible outline of Ireland. Considering that Ptolemy constructed this map in the late second century AD and Britain was much more than a thousand miles away by sea, the accuracy of his work is truly astonishing.

Little wonder then that Claudius Ptolemy has come to be known not just as the last, and perhaps the greatest, of the classical astronomers, but as the father of geography too.

Claudius Ptolemy’s achievement was to lay out a whole system by which the world, the universe, and indeed the fates of men might be known. In it he hoped to live up to the ideals of Alexandrian philosophy, ideals which had been known to Eratosthenes, Callimachus, and Aristarchus before him. In this, for all its failings, Ptolemy’s work was a spectacular success. What he could never have known as he wrote, however, was that his system would provide the framework for a new age, the Christian age, which was already sparking to life in the streets around him.

CHAPTER FOURTEEN

DAWN OF THE ICONOCLASTS

Clement of Alexandria,
Stromata

 
 
F
or Ptolemy, Philo, and the Alexandrian philosophers in whose footsteps they trod, spiritual enlightenment came from two interconnected sources. It was in the unending search for wisdom which might allow them to see beyond the sordid, material world to Plato’s. Coupled with this was a personal code by which their bodies and minds might be in a suitable condition to search out such truths. This path was by no means easy, requiring moderation and temperance, a willingness to shun the obvious temptations of the physical world and to strive to find divinity in ideas alone. As such it was a path suitable only for the chosen few. Neither Philo nor Ptolemy believed that just anyone could enjoy the insights they had received. They were the highest link in the human portion of the Great Chain of Being, with the privilege, and perhaps the duty, of understanding the world on behalf of lesser humans—the uneducated, the women, and the children.