Al-Ferghani

Near the old governor's mansion of Ferghana is a leafy park dedicated to Ahmad al-Ferghani (c. 830 CE), polymath philosopher (and lamentable engineer), known to Europe as Alfraganus.

Throughout the 'middle' ages, the lands across the Oxus had given birth to a significant number of men of ideas -- the various Als of Khwarizm, Birun, Bukhara, Chach, Ghujdawan, Ferghana and Margilon -- and they have been collectively called The Pleiades of Transoxiana. In the Indian system of astronomy, the seven sisters of the Pleiades are called the Krttika (Murugan, raised by the sisters, is thus Kartikeya); the Sanskrit word means 'The Cutters', and is the root for all things critical, i.e. those in the house of Krttika aim to penetrate underlying causes.

Like many of the 9^th century philosophers of Mawarannahr (literally, the areas beyond the nahr Oxus or Amu Darya), al-Ferghani was a Tajik-speaker whose ancestors were likely forcibly converted from Zoroastrian, Hindu or Buddhist faiths after Arab conquest. He came to be one of the members of the team of astronomers at the court of Caliph al-Mamun of Baghdad who calculated the diameter of the Earth using measurements of the meridian arc length. His Kitab al-Fusul Ikhtisar al-Majisti (Book of Chapters Summarizing The Almagest), written c. 833, was a translation (and emendation) of Ptolemy's greatest work, updated from al-Ferghani's own calculations and enlarged in places with his own opinions where different from the Ptolemaic.

From a paper on al-Ferghani's works:

The Greeks divided the spherical earth into 360 degrees, but differing sources gave different information about the length of a degree. We know today that the correct measurement is about 111 kilometers per degree at the equator. In the third century BCE, the Greek astronomer Eratosthenes, the director of the library in Alexandria, came up with the remarkably accurate calculation of 110 kilometers (59.5 nautical miles) per degree; in the second century BCE, the great Alexandrian geographer, Ptolemy calculated the length of a degree to be 93 kilometers (50.3 nautical miles). Alfraganus calculated it and decided that the value should be 111 kilometers (56⅔ nautical miles). In this case, his value was more accurate than Ptolemy's.

Al-Ferghani's Kitab was translated into Latin in the 12^th century and remained very popular in Europe till past the time of Dante (1265-1321). The Divine Comedy borrows in many places from Alfraganus, Dante had clearly studied it closely.

Alfraganus states that the heaven of fixed stars moves from west to east about one degree of arc every century. Dante says the stars had moved 1/12 of a degree between the time Beatrice was born to the time he first met her, and thus she would have been 100/12 or just over 8 years old at the time of their first acquaintance.

The constellation of the Southern Cross, as prominent in the Southern sky as Orion is in the Northern one, is circumpolar south of 34 degrees S latitude and visible thence every night of the year. April to June, viewers south of the Tropic of Cancer (currently 23.438 degrees N latitude) can glimpse the Southern Cross rising just barely above the southern horizon. Once the Cross had been easier to see from the Northern Hemisphere. The Ancient Greeks knew its four stars (they counted them among the constellation Centaurus), and the Cross certainly appeared in the sky of the Middle-East around the time of Jesus of Nazareth. The slow precession of the Earth’s axis has carried Cross southward, and its stars haven’t appeared north of the Tropic of Cancer for more than a thousand years. However, Ptolemy knew the constellation, as well as its drift in the heavens, and al-Ferghani updating Ptolemy figured that by his time in the 9^th century CE, they would be somewhere over the South Western ocean, or over a terra incognita far, far beyond Africa. Dante the poet decided this unknown land was Purgatory, and there he placed the 4-starred Cruz described by al-Ferghani.

(When Dante and Beatrice finally ascend from Purgatory on the far side of the world, they see four brilliant stars which the Divine Comedy says represent the four principal virtues -- Justice, Prudence, Fortitude, and Temperance -- and which hold out the symbol of redemption to the sinner:

“To the right hand I turn’d and fix’d my mind
On the other pole attentive where I saw
Four stars ne’er seen before save by the ken
Of our first parents. Heaven of their rays
Seem’d joyous. Oh thou northern site, bereft
Indeed, and widow’d, since of these deprived ...”

From The Divine Comedy, Canto I in the Vision of Purgatory.)

During his last voyage to 'India' in 1501–1502, Amerigo Vespucci and Gonçalo Coelho sailed south along the coast of South America to the bay of Rio de Janeiro. If his own account is to be believed, Vespucci subsequently reached the latitude of Patagonia, though this seems doubtful since he does not mention the broad estuary of the Rio de la Plata. Anyway, Vespucci had gone far enough south to see the Southern Cross; when he saw the stars in the sky as described by al-Ferghani, he is said to have exclaimed "Ah! We've arrived at Dante's Purgatory!"

On his return to Lisbon, Vespucci wrote in a letter to the Medici that the land masses he had explored had been much larger than the India described by Ptolemy and Marco Polo, and therefore must be a new world.



Christopher Columbus also knew his al-Ferghani, and put forth arguments based on the circumference of the sphere that were derived from al-Ferghani's Kitab. In 1490, most scholars accepted Ptolemy's claim the terrestrial landmass (for Europeans of the time, comprising Eurasia and Africa) occupied 180 degrees of the sphere, leaving 180 degrees of water. Columbus, keen to attract funding for his voyages, went about finding a number that would support a lower distance. Petrus Cardinal Aliacensis, in his Imago Mundi and Cosmographiae Tractatus, following Marinus of Tyre (Ptolemy's guru), had put the landmass at 225 degrees, leaving 135 degrees of water. The good Cardinal (b. 1351) , however, had known nothing of Marco Polo's description of the enormous east-west span of Asia. Columbus subtracted 28 degrees to account for the breadth of Cathay, and another 30 degrees to allow for Cipangu (Japan) being, as reported, some distance off the coast of Cathay. A further 9 degrees could be deducted if one left from the Canary Islands -- this left 68 degrees to be traversed.

But how much to a degree? The good thing about standards, it is said, is that there are so many to choose from. Columbus declared one degree represented a shorter distance on the earth's surface than was commonly held -- he (mis)read the writings of al-Ferghani as if the distances had been calculated in Italian miles (1,238 meters). Accepting the length of a degree to be 56⅔ miles he therefore reckoned the distance from the Canary Islands to Japan was not as vast as feared:

According to a note in his own hand in his copy of "Imago Mundi," Columbus navigated by the erroneous calculations of the 9th century Arabian astronomer Alfraganus. Using Alfraganus' value of 56 and 2/3 land miles per equatorial degree, Columbus assumed that he had only to sail approximately 2,500 miles westward from the Canary Islands in order to reach the Orient. Columbus asserted that his voyages had confirmed the cosmography of "Imago Mundi" and the calculations of Alfraganus. Columbus himself thought that he was navigating according to Alfraganus' value and he wrote: "Observe that in sailing often from Lisbon southward to Guinea, I carefully measured the course ... and in agreement with Alfragan I found that each degree answered to 56 and 2/3 miles. So that we may rely upon this measure."

What Columbus had not realized was that al-Ferghani had used the much longer Arabic mile (about 1,830 meters); also, the correct longitudinal distance between the Canary Islands and Japan is 165 degrees. This makes the distance from the Canary Islands to Japan about 20,000 km -- no ship in the 15^th century could carry enough food and fresh water for such a journey. Most European sailors and navigators had concluded, correctly, that sailors undertaking a westward voyage from Europe to Asia non-stop would die of thirst or starvation long before reaching their destination.

The monarchs of Spain, however, having settled an expensive war of succession with Portugal, and desperate for a competitive edge over other European countries in the trade with India, decided to gamble on Columbus' theory. Fortunately for Columbus and his crew, there was something in the middle; the span of the Caribbean islands from Puerto Rico to the Bahamas are 50-60 degrees away from Europe, more-or-less within the bounds of the 3500 miles his ships had been provisioned for! As the 16^th century developed, a route to the Americas, rather than to Asia, gave Spain an overseas empire; Columbus, of course, died convinced that his calculations had been correct, and that he had indeed found India.



There were cases where wrong calculations were not so serendipitous. According to ibn Taghribirdi, that gossiper on 3000 people, the great Caliph Jafar al-Mutawakkil had entrusted two sons of Musa ibn Shakir with the digging of a canal to be named al-Ja'fari. The canal was to run through the new city al-Mutawakkil had built near Samarra on the Tigris (and named al-Ja'fariyya after himself.) The sons delegated the work to al-Ferghani, who was not much of an engineer, and miscalculated (or tried to take a shortcut, some of the terrain being rocky and hard to dig), making the beginning of the canal deeper than the rest. In the end, water could run through the length of the canal only when the Tigris was running high. News of this angered the Caliph, and the two brothers were saved from severe punishment only by the gracious acquiescence of Sind ibn Ali, the celebrated Indian colleague of al-Khwarizmi who had created the first star tables known to the Muslim world, to become a co-conspirator and vouch for the correctness of al-Ferghani's calculations (in the process risking his own neck.) However, another serendipitous event -- the estranged son of the Caliph got his father assassinated by a Turkish solider -- saved both al-Ferghani and ibn Ali from almost certain death.

The crater Alfraganus on the moon is named after al-Ferghani.



We get ready to leave Ferghana town, intending to head towards Andijon, synonymous in the last few years with the worst massacre since Tienanmen of a body of protesters by their own government. (A brief backgrounder below.) Our new driver is Timur. He was in Andijon the day prisoners were sprung from its notorious jail. "People were dancing and cooking plov on the streets," he recounts laconically, "they all thought Karimov was gone." The next night, he woke up at 2 am to the rumble of trucks. All night long, from behind the curtains of his apartment across the street from the government hospital of Fergana, he watched bodies wrapped in white sheets being carried in to the morgue by masked men. Tanks had sealed off his street.