Measuring time and space. Generations 451-454, 1000-1080

Towards the end of this period a metalsmith in Toledo devised a universal astrolabe. His name was al-Zarqali, known later in the west as Arzachel.

earliest surviving astrolabe

Astrolabes were made of brass and were things of beauty. This one is from Iran, a century earlier. (Image from UC Santa Barbara) 

The astrolabe was a glorified protractor, but much more sophisticated. It allowed a person to measure the positions of the stars and planets, thereby enabling them to determine local time. It had been devised by the ancient Greeks, but had a drawback: each one was valid only for a given latitude. Al-Zarqali’s astrolabe had the advantage that it could be set for any latitude and so was much more useful. Over the following centuries it became known in northern Europe as a Saphaea. Abelard and Heloise, in Paris in the following century, named their son Astrolabe. Chaucer describes the use of one in the Canterbury Tales a couple of centuries later still. Astrolabes were leading-edge technology until the development of the telescope in the 1500’s.

Astrolabes were also used to measure the heights of buildings.

measuring height with an astrolabe

Here is a much later image, from the 16th century, demonstrating its use. (Image courtesy of the Whipple Library, University of Cambridge)

The muslim world stretched from Toledo across North Africa, through the middle east to what is now Afghanistan. The use of the astrolabe demonstrates a new departure in thinking that was taking place across this world. It used mathematical principles (straight lines, perfect numbers) to describe the observed world where lines are never straight and numbers never quite add up. For the ancient Greeks the two were irreconcilably separate. But islamic scholars demonstrated that precise mathematical principles could be used to describe the fuzzy physical world.

One of the greatest scholars lived at the eastern end of this world, between the Caspian Sea and Afghanistan. Al-Biruni was so influential that some have described the first half of the eleventh century as ‘the age of Al-Biruni’. Because the caliphs in Baghdad 1500 miles or 2500 km away were retreating behind the protection of their Mamluk guards, this region was left to fend for itself, and so al-Biruni lived in a time of political turmoil. Depending on who was ruling at any time he moved from one town to another, always continuing his wide-ranging researches.

He wrote a history of India, based on reports from captured Indian scholars brought back from the campaigns of one of his rulers. This was the first known dispassionate study of another culture, a heathen one at that, not one of a people of the Book. Here is an extract:

“With regard to God, the Hindus believe that he is one, eternal, without beginning and end, acting by free will, almighty, all-wise, living, giving life, ruling, and preserving; one who is unique in his sovereignty, beyond all likeness and unlikeness, and neither resembling anything nor having anything resemble him. In order to illustrate this, we shall produce some extracts from the Hindu literature, lest the reader should think that our account is nothing but hearsay.”

He wrote a book on pharmacology in which he listed each plant in five languages. And using the astrolabe and islamic advances in trigonometry, he developed a method to measure the circumference of the Earth.The previous best attempt had been in Egypt, and involved placing a stake in the ground in Cairo, pacing the distance north to Alexandria, and then measuring the angle of the sun’s shadow at each place. Al-Biruni introduced his method with the following sentences: ‘Here is another method for the determination of the circumference of the Earth. It does not require walking in deserts.’ (quoted in ‘Pathfinders’ by Jim Al-Khalili, Puffin Books)

Travelling on his patron’s military campaigns in Pakistan, he saw a mountain surrounded by a plain near the fort of Nandana, which was just what he needed to apply his new method. In a two-stage process, he first calculated the height of the mountain from the plain. Then he climbed to the top of the mountain and measured the angle to the horizon.This gave him the first triangle ABH in the diagram.Then by calculating the distance to the horizon he could project a second, larger triangle with the same angles between the mountaintop, the horizon and the centre of the Earth, triangle ACS.


I don’t understand the maths myself, but I can see that the angle marked θ has the same value at the centre of the Earth, at ground level and between the top of the mountain and the horizon line, that another angle is a right angle and so the third must also be equal.

How ingenious! The calculations presupposed that the Earth was a perfect sphere and scientists now tell us it isn’t quite, but his work displays a confidence in the human ability to make sense of the world around us. The age of al-Biruni indeed.

Generations 453-455, 1040-1100. Constantinople calls for help

(As I said in my last post, I feel that I am travelling without a map. This post is an outline map. If it was in a book it would be in a textbox, next to the main narrative. It gives the background for the story I am interested in, which is not about kings and battles but ideas and perceptions.)

During the eleventh century there was an unstoppable movement of people expanding out from central Asia, and another uncannily similar one in northern Europe. Constantinople was caught between them, and suffered the attentions of both.

Let’s look at the Asian one first. For a long time the caliphs in Baghdad had bought boys in the slave markets on the northern border of their empire, from what is now Turkmenistan. They were mistrustful of local arab or persian vested interests and so chose an imperial guard who would be loyal to them alone.The boys were kept separate and trained to be the caliph’s personal bodyguard. They were known as the mamluks, the slaves. For most people in Baghdad the mamluks were the nearest they got to the caliphate. Eventually the caliph moved them out of Baghdad to Samarra, and then moved there to be with them.

The qualities that made the mamluks so desirable as elite soldiers were there also in the people left behind. They were brave and strong. One clan, the Seljuks, expanded out of Turkmenistan in 1040 and became known as the Seljuk Turks. They soon adopted islam, in a rough-and-ready version that suited them. They had no written language and didn’t bother to learn Arabic, the language in which the Qu’ran was written. In their rapid wave of conquest they left the caliphate alone and adopted the title of sultans, the sword arm of the caliphate.

Khorasan province, over the border from Turkmenistan in northern Persia, was undergoing a cultural renaissance at this time. The Seljuk prince to whom it was assigned appointed a brilliant Persian administrator, Nizam al-Mulk. When the prince became sultan in 1053, he took his accomplished secretary with him. In so doing, he was playing to the strengths of each culture. The Seljuks were the fighters, the sultans, the Persians with their sophisticated culture were the viziers, the administrators. And the Arabs, with their legacy going back to Mohammed four hundred years previously, carried the law.

Nizam al-Mulk (meaning ‘Order of the Realm’) organised tax collection, set up communication systems and a police force. But he is most remembered for the establishment of institutes of higher education. They were named ‘nezamiyah’ after him. They were sponsored by the ruling families and the elites.The brilliant thinker Al-Ghazali, whom we have already met, was appointed to run the nizamiyah in Baghdad in 1091.The nezamiyah inspired the establishment of madrasas across the muslim world, and some say that European universities can also be traced back to them.

khorasan_map_smImage courtesy of the Textile Museum, Washington DCUSA

The new sultan was named Alp Arslan, ‘heroic lion’, by his troops. He was over six feet tall. It was said that he grew his moustache so long that when he rode his horse it flew behind him like twin braids. Alp Arslan and his army moved along the southern shores of the Caspian Sea, along the edges of the Empire. By 1068 they had reached the Byzantine Empire in Anatolia.

Well, now we call it the Byzantine Empire. At the time it saw itself as a continuation of the Roman Empire, tracing its lineage back to Emperor Constantine and beyond. This was where the Roman Empire had adopted christianity. The current emperor, Romanos IV Diogenes, decided to take the invaders on.

With a large but ill-equipped, undisciplined army he was able to keep them at bay for three years. Alp Arslan was wary of confronting Romanos head-on, but the two armies eventually met at Manzikert in what is now eastern Turkey in 1071. Romanos was unlucky, lost the battle, was captured and brought to Alp Arslan. Surprisingly, Alp Arslan did not kill him but released him with the promise of a large ransom.

Map_of_the_Anatolian_Seljuk_SultanateManzikert is just north of Lake Van, below the ‘E’ of Armenia. Image courtesy of Muslim Heritage

Romanos IV did not survive the humiliation on his return to Constantinople. He was deposed, blinded and exiled. He died of his wounds from the blinding, in 1072 at the age of 42. Alp Arslan himself died the same year and at same age, murdered while on campaign in his ancestral homelands of central Asia.

The victors named their new territory the Sultanate of Roum, after the Roman Empire that they had won it from. In time it became known as Turkey.

Now we need to skip across a continent, to north-west Europe. A few centuries earlier a similar group of brave and fierce-looking invaders had moved out from Scandinavia in their beautiful sleek boats. They colonised Greenland and Iceland to the north-west. They travelled Russia through the river systems, making settlements as far south as the Caspian Sea and near Constantinople itself. They also moved down the North Sea and repeatedly raided settlements in the British Isles. In the tenth century one group settled in northern France, where they became known as the men of the north, Norsemen, and eventually Normans. Their land became known as Normandy. They adopted the local language and religion, and then set off on another wave of conquest in the period under discussion. I suspect that 1066, the year of the Norman invasion of England, is engraved on the English national psyche just as strongly as 1789 is in the French or 1776 in the USA.

In the early eleventh century some Normans went on pilgrimage to Jerusalem, and on the way back found some opportunities to do what they did best: fighting. Sicily was under muslim control and a large part of southern Italy was ruled from Constantinople. In 1047 Robert Guiscard, the sixth son of a minor noble and so with no prospects at home in Normandy, arrived with five horsemen and thirty foot-followers to take his chances. By 1070 he was the ruler of southern Italy and Sicily. A generation later his son was crowned king of Sicily.

The historian Anna Comnena, the daughter of Romanos’ successor Alexius Comnenus, was fascinated and appalled by the Normans. Here is what she had to say about Robert Guiscard:

“This Robert was Norman by birth, of obscure origins, with an overbearing character and a thoroughly villainous mind; he was a brave fighter, very cunning in his assaults on the wealth and power of great men; in achieving his aims absolutely inexorable, diverting criticism by incontrovertible argument. He was a man of immense stature, surpassing even the biggest men; he had a ruddy complexion, fair hair, broad shoulders, eyes that all but shot out sparks of fire. In a well-built man one looks for breadth here and slimness there; in him all was admirably well-proportioned and elegant… Homer remarked of Achilles that when he shouted his hearers had the impression of a multitude in uproar, but Robert’s bellow, so they say, put tens of thousands to flight.” (from the Alexiad of Anna Comnena)

The invasion of Sicily marked the beginning of the slow decline of muslim occupation of Europe. In 1085 the christian rulers of northern Spain captured Toledo from the muslim rulers. Al-Andalus was also in political disarray at this time after the disintegration of the central caliphate in Cordoba in 1031. It was known as the Taifa period, a taifa being a small emirate. From then on, the many states in al-Andalus never became strong enough to resist the christians from the north for long.

Muslim merchants were not permitted to settle in non-muslim countries, but christians and jews were. This period saw the beginning of the Italian trading city-states, first Amalfi, Pisa and Genoa, and later Venice. Another factor leading to the decline of muslim power and the beginning of the end of the muslim golden age?

There was one more destabilising factor in this period, a really strange one. South of the Caspian Sea not far from where Alp Arslan’s army would have marched, a teacher called Hassan-i-Sabbah captured the mountain fortress of El-Alamut, the Eagle’s Nest, in 1090. He was a member of a shia sect (definitely not mainstream shia) and he was going to put a stop to those sunni Seljuks. He didn’t have a large army so he turned to the most effective way he could think of. He trained young men in the art of political murder. They became known as the assassins. They planned each assassination well in advance for maximum impact. Most of them were carried out in public, during Friday prayers. The assassins themselves expected to be killed straight after they had accomplished their mission, as indeed they invariably were. Nizam al-Mulk, Alp Arslan’s secretary, was one of their victims. The assassins continued their activities, adding another layer of fear in an already uncertain world, until the Mongol invaders captured El-Alamut over a century later.

This is the context of the Crusades, which began in 1095. The Seljuk Turks with their robust version of islam were less tolerant of pilgrims to Jerusalem than the shia Fatimid caliphs, based in Cairo, whom they replaced. The news of harsh treatment at the hands of unbelievers began to filter back to Europe. Secondly Romanos’ successor as Emperor of Constantinople, Alexius Comnenus, decided to overcome his dislike of the papacy and ask for help against the Turks. He was concerned that otherwise they might be wiped off the map. He sent a delegation in 1095, to meet the pope at Piacenza.

Alexios_I_KomnenosAlexius Comnenus

The request reached a pope who had difficulties of his own. Pope Urban continued the work of his predecessors, trying to carve out the authority of his church and impose it on rulers such as Robert Guiscard and the equally troublesome German Emperor. Giving them all an external enemy seemed a perfect opportunity. But not to save Constantinople: Jerusalem would be the target. Recover the holy places from the saracens! (even though they had been under saracen control for the last 400 years).

He launched the idea in a speech at Clermont in central France in 1095. As an incentive, he announced that those who agreed to do this from devotion rather than the prospect of honour or gain would be absolved of their sins when they died. In other words, it didn’t matter what dreadful things they did while on crusade because they would be going to heaven anyway. And some dreadful things were done.

The appeal was successful way beyond Urban’s expectations. The main crusader army set off two years later, in 1097. Ironically, the vanguard of the army were Normans, some of whom were related to Robert Guiscard. No wonder Alexius Comnenus didn’t let them in when they arrived at Constantinople.

Note: much of this post is based on chapter 8 of Destiny Disrupted, a history of the world through islamic eyes by Tamim Ansary. Highly recommended.

Going off the edge of the map. 1100 CE

So far in our story there has been a largely agreed-to narrative.

We began in the current generation, generation 500, with its unprecedented level of interconnectedness and availability of information. As we explored back through the twentieth century we saw how technological innovations, initially available only to the rich, eventually empowered so many more of us. Mobile phones, computers, washing machines, air travel, for example.

Then we moved back through the Industrial Revolution of the nineteenth century. This saw technological breakthroughs and also a change in thinking. Areas previously deemed off-limits to the uninitiated were now open to question. Charles Darwin, a country vicar living in the south of England, wrote ‘The Origin of Species’ and sparked a furore which still continues in some places.

The eighteenth century saw the Enlightenment. Some people felt empowered to question established ways of organising society and describing reality. They wrote about it and talked about it in the coffee shops of Paris, London and elsewhere. The Enlightenment also saw the birth of a powerful idea, that no man has the right to own another. (Women were a grey area but the principle was established. It took another century for the same rights to be extended to them.) The same expansive sense sent men around the world. Australia and New Zealand were colonised by Europeans. Clipper ships brought cargoes of tea and spices from the East to London and Rotterdam.

And so we can continue back with a recognisable strand of events, each generation building on the achievements of the previous one. The story has been agreed. Most history books that we read will pick up on a part of this narrative.

But I have reached a break. In the year 1100 the largest city in Europe was Cordoba. I never knew that! This wasn’t covered in any history lesson I remember. In comparison to the Europe we have largely focused on so far, the muslim world of 1100 was vast. A scholar from northern Persia could travel to Baghdad or Damascus (both much bigger cities than Cordoba),  meet someone from Toledo there, and converse in their common language of Arabic to exchange ideas and experiences.

My problem is that I can’t find the map of the world I am about to enter. I have found a lot of sources, but they all tell slightly different stories. The maps don’t quite match each other, and there are a lot of blank spaces. But while the lack of a map makes this world more difficult to explore, it also is much more interesting for me.

I will have to abandon the approach of one generation at a time. Perhaps because the muslim world is so big, ideas and innovations no longer fit into tidy twenty-year slots. So the next entry in the blog will explore the world-changing events that occurred between 1050 and 1100 (or thereabouts).

Generation 458, 1140-1160. Measuring the world

This generation saw the appearance of a new style of church architecture in northern France.  Nothing like it had been seen before. As with all innovations, it was able to appear because of a combination of circumstances: the opportunity, the motivation, and the people to put it into effect.

First, the opportunity. The latin world in the previous generation had seen a publishing sensation. Adelard of Bath had travelled to the moslem world in search of learning, as had so many others. He was away for seven years, spending most of them in Antioch in present-day Turkey. There he translated books from arabic into latin. His translation of Euclid’s Elements of Geometry was world changing. If you studied geometry at school, a lot of it can be directly traced back to this book, originally written as a textbook by Euclid of Alexandria in the third century BC. A triangle has 180 degrees? Euclid. If you draw a diameter of a circle, then draw a line from each end of the diameter to any point on the circumference, they will meet at right angles. Ditto, Euclid. Pythagoras’ theorem (3 squared plus 4 squared equals 5 squared is the best known example) can be traced to Euclid’s Elements.

As well as the content of the book (which meant that buildings could be designed more effectively than before) Euclid’s method of reasoning was simple, irrefutable and new to the latin world. He set up a series of five axioms, which now seem self-evident. The first axiom, for example, is that a straight line is the shortest distance between two points. He went on to introduce problems, and solved them with logical proofs.

islamic arch

Euclid’s work was well known in the islamic world. This arch from Madrid in al-Andalus, from the previous century, would have been impossible to build without an understanding of the principles of geometry. The pointed arch was a regular feature of islamic architecture.


This prayer niche from the Ibn Tulun mosque in Cairo clearly shows the pointed arch. It was built three hundred years previously, in the ninth century. 

But it was new to the latin north. Adelard’s translation went to the cathedral schools, where it encountered a different culture. It was not by accident that the church was called the Roman Catholic church. It continued the Roman Empire’s love of large structures. Large churches were not new, therefore, but what this technology allowed was a new departure in their construction. Now they could let the light in, applying the same skills in a very different expression.

Saint-Denis in Paris, Sens in Burgundy, Laon in Picardy – all were rebuilt in the new style in this generation. The builders treated the stone as a framework for the windows, using rib-vaulting and pointed arches, and filled the windows with coloured glass (another technique learned from the moslem world).

Sens cathedral

Here is the interior of Sens cathedral, with the soaring columns and huge windows of the new Frankish style, now known as Gothic.

Five centuries later the architect of St Paul’s Cathedral in London, Sir Christopher Wren, came to the same conclusion. In his ‘Parentalia’ or Memoirs, he writes, ” … what we now vulgarly call the Gothic, ought properly and truly to be named the Saracenic architecture refined by the Christians…”

In 1145 Chartres Cathedral burned down, and the opportunity was taken to rebuild it in the new style. The project was not completed until the following century, but this is where it started. There is a statue of Euclid at Chartres, as one of the representatives of the liberal arts. Luckily for us, Chartres became a backwater over the subsequent centuries, overshadowed by Paris. This meant that nobody could afford to modernise the cathedral, and so it can still be seen largely as it was eight centuries ago.

The word ‘geometry’ literally means ‘earth measuring’. The same rigorous enquiry found different expression in the south of Europe during this generation, but applied to geography (‘earth drawing’). The most accurate map and accompanying description of the world, with the unlikely title of the ‘Book of Roger’ was produced in Sicily in 1154. It set the standard until the time of Mercator, three hundred years later.

The population of Sicily was still largely moslem, as it had been reconquered from the arabs less than a century previously. Palermo, the capital, had several hundred mosques. Like his grandson Frederick II whom we have already met, the Norman king Roger II of Sicily embraced arabic culture. He was dissatisfied with the maps available and in the arabic spirit of enquiry he decided to compile a better one. He commissioned a displaced aristocrat from al-Andalus, Muhammad al-Idrisi, to coordinate the project. Over fifteen years al-Idrisi interviewed travellers, compared their stories and finally put together an authoritative description of the known world, from the Canary Islands to Korea.


There was an engraved map on a large silver plate to accompany the book. In the conventions of the time, north is at the bottom of the map and south at the top. So Asia is on the left, Africa at the top and Europe at the bottom. Both the silver plate and the original book were destroyed in riots shortly after they were finished but many copies remain.

A copy of the book is online here, and it is exquisite (even if you don’t read arabic. The maps are over two pages, so each double-page image is a map and the single pages are text.)


There was  a smaller world map in the book, with Africa at the top and Europe at the bottom. It is said that this map inspired the Portuguese explorers to attempt to sail around Africa, as it is shown surrounded by sea.

There were other towering figures in this generation. Abbess Hildegard of Bingen wrote extensively, composed and corresponded. One of her correspondents was Bernard of Clairvaux, another influential person. He  joined the Benedictine order as a boy and wanted to reform the order, advocating a simpler life. He encouraged the establishment of monasteries in remote areas where they could be self-sufficient, living off the land. He was so driven that in his lifetime he was instrumental in the establishment of six hundred Cistercian monasteries (named after the first monastery he joined at Citeaux). He also campaigned to launch the second crusade to the Holy Land in this generation.

But the order Bernard attempted to reform had its own powerful individual. Peter the Venerable was the abbot of Cluny, the mother house of the previous wave of expansion and establishment of monasteries. He was an open-minded man who advocated understanding the saracens rather than trying to annihilate them. Especially as the second crusade turned out to be a disaster for the christians. He travelled to the Cluniac monastery of Santa Maria La Real in Najera, south of the Pyrenees, and from there to Toledo where the translation movement was in full flood. He persuaded two translators, Robert of Ketton (from a village near Rutland in present day England) and his friend Herman of Carinthia (a region in present-day Austria), to give up their attempts to translate Ptolemy’s Almagest and translate the Quran instead. Called the ‘Law of Mohammed the False Prophet’  the title shows his less-than-dispassionate approach to the subject. But at least the intention was there.

By a strange twist of fate, Robert of Ketton ended up as canon in the church at Tudela, not far from Najera. Tudela is the town from which rabbi Benjamin  set off on his travels in the following generation. So the two men almost certainly knew each other.

There was another English Robert participating in the translation movement at this time. Robert of Chester went to Segovia in al-Andalus. He translated the book that introduced Algebra to the latin north: al-Khwarizmi’s Liber algebrae et almucabola, written three centuries previously.

Generation 465, 1280-1300. Assimilating new influences

For this generation, one of the most exciting places to be was Toledo in Spain. This was the high point of the translation school, in which moslems, christians and jews collaborated on the translation of books from arabic, greek and hebrew. Scholars came from northern Europe to meet and work with the translators. King Alfonso X of Castile requested that the translations be made into Castilian Spanish, not Latin as had previously been the norm, to make the learning more widely accessible.  This had the side-effect of establishing Castilian as a national language, just as Dante’s decision to write in the vernacular established the Italian language in the following generation. By the end of this generation Alfonso was dead and the school was disbanded by his successor.

However, its influence was felt. This generation also saw the peak (literally) of gothic cathedral-building. The highest church nave ever was attempted at Beauvais in northern France. Part of it collapsed when the builders pushed beyond the limits of what was possible. But they rebuilt the nave, with more reinforcements, reaching a height of 48 metres.

choir beauvais cathedral

I suspect that as we go on in our story we shall see the influence of muslim architects and glassmakers in the inspiration for these breathtaking, magnificent buildings that are still to be seen across northern Europe from Britain through France to Germany. Standing inside one of these marvellous churches today we can feel the resonances, perhaps even register something of the new influences that the builders were responding to and trying to give expression to.

But back to Spain. During this generation the merchants from Catalonia, particularly Barcelona, played a greater part in the Mediterranean trade that had hitherto been dominated by Genoa, Pisa and Venice. Aragon (which included Catalonia) was extending its influence.

The Aragonese profited from an abuse of power that took place in Sicily, for example. Sicily had been another place of meeting of influences, from the muslim world, the Mediterranean and northern Europe. A generation previously a French pope had imposed a French king on the Sicilians, having fallen out with the previous incumbent and even launched a crusade against him. Once installed in Sicily, the new king Charles of Anjou started to to have ambitions, even making plans to invade Constantinople. For this he needed funds, so he taxed the Sicilians.

But sometime people are pushed too far. After Vespers on the evening of Easter Monday, March 30th 1282 outside a church in the Sicilian capital of Palermo, a French soldier made an inappropriate advance to a Sicilian lady. Her husband came to her defence and attacked him, killing him. The husband’s compatriots joined in. Within a month or so thousands of French had been killed. Charles gave up his claim to the island and with it his plans for a pan-Mediterranean empire. A relative of the dynasty he had ousted with the pope’s help was married to a prince from Aragon. And so the Aragonese came to Sicily.

Further north in Italy, the power struggles of the merchant city-states had an unintended consequence. Genoa sent a navy into the Adriatic, to challenge Venice. They defeated the Venetians and took the surviving crews of the galleys as prisoners back to Genoa. One of the prisoners was a merchant called Marco Polo, who ended up in a room in Genoa with a poet called Rustichello from Pisa. Marco told Rustichello the story of his travels along the Great Silk Road, the time he spent in the service of Kublai Khan in Cathay, and his return by sea. Rustichello wrote it all down.

Marco Polo was able to make this trip because the Mongols had joined up the known world. It was possible to travel across central Asia, and he was not the only one to take advantage of the opportunity presented to him. A couple of generations previously a friar from Flanders, William of Rubruck, had made the trip to Karakorum in Mongolia, the headquarters of the Mongol Empire. Once there, he found French and German craftsmen living and working in the town.

Clearly, some people felt that it was safe to travel to central and eastern Asia. This suggests to me that there was more to the Mongols than the mindless violence for which they are mostly remembered in the west. Both William of Rubruck and Marco Polo described with respect and admiration the organisation of the societies they met, the variety of religious beliefs (including Nestorian Christians, Saracens or muslims, and idolaters, probably buddhists) and the open-mindedness of the khans. They were both invited to participate in public discussions with adherents of other religions about the merits of their different beliefs.

This opening of communication with the east must have had consequences in the west. To hear about countries and civilisations more sophisticated than one’s own is a lot to take in. It must alter a person’s view of the world.

In the moslem world, the place to be was Cairo. After the destruction of Baghdad by the Mongols in the previous generation, many of the scholars had made their way here.

To take a couple of examples:

Ibn al-Nafis wrote a description of the circulation of the blood which overturned Galen’s view that arterial and venous blood were separate, and described how the blood mixes with air in the lungs. It could be reasonably asserted that the discovery of the circulation of the blood should be attributed to him rather than the Englishman William Harvey 350 years later.

Qutb al-din Al-Shirazi was a scholar and diplomat, originally from Shiraz in Persia, who probably met Ibn al-Nafis when he was sent on a mission to the Mamluk sultans of Egypt in 1282. He identified previous astronomical observations as transits of Venus.

Qutb al-din al-Shirazi's manuscript

Here is a page from one of al-Shirazi’s manuscripts further exploring one of the perennial problems for muslim astronomers: the movement of the planets.

During this generation the Mamluk sultans also evicted the crusaders from their last stronghold in the holy land, from Acre. The Frankish kingdom of Outremer was no more.