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Lecture: Roman, Byzantine and Arab Worlds

The story of the expansion of Rome is a military adventure, but it is also a technological adventure. As the western half of the Empire fell to the barbarian invaders, Byzantium preserved Greek and Roman methods. By the 9th century, Arab scholars had not only reclaimed this knowledge but moved it forward. Technology during this era of "Late Antiquity" was used to hold together an empire and recover lost knowledge.


The Roman Republic, according to legend, was founded in 509BC with the overthrow of the monarchy. During the 5th and 4th centuries BC, Rome expanded from the center of the Italian peninsula, both northward to defeat the Etruscans and southward to the Greek colonies. I find it interesting that in this expansion, Romans always saw themselves as defending from attack rather than conquering and expanding.

Farming was the main activity of many in the Republic, and we can see some of the techniques by reading Cato. He was one of the first to write texts in Latin rather than Greek (the language of the intellectual world at the time), and he wrote a book on farming called De Agri Cultura. Among the advice he offered was the use of compost and manure to ensure good yields, ploughing deeply so that surface roots don't form on olive trees, and the use of amurca (olive oil sediment) as a pesticide. It is all practical - there is no reference to science even though Cato himself was a learned man. In additional to providing practical techniques, Cato's book glorified the role of the farmer in Roman life.

That said, many Roman men spent time soldiering, even if they were farmers. As Rome expanded, competition occurred with goods for the new regions (Sicilian grain, with its lower price, is one example), and farming became a more difficult way to earn a living. Military technological advancements were often achieved by improving on Greek technologies. One example is the javelin, a throwing spear. Javelins were the first line of attack in a Roman battle, but they didn't always kill. The head was designed to twist on the shaft as the point entered a shield. This meant the javelin couldn't be recovered, but it also meant it was hard for the enemy to remove, which they had to do to make the shield useful again. The enemy thus spent valuable time trying to pull out javelins while the Roman army attacked with swords. The Greek catapult was improved, adding pins and holes to improved accuracy. Catapults were basically siege engines, whose purpose was to beat down the walls of a fortification.

The Roman Empire

As the Republic became an Empire (around 27 BC), Roman technologies focused on construction that tied Rome's disparate territories together while demonstrating Rome's glory. The centralized government could order and pay for major projects.

aqueductAqueducts served multiple purposes. Designed to carry water from distant snowpacks to lowland towns, they were built to a high standard. Stone arches supported clay-lined channels above, which could then be diverted into different areas of town. In Rome itself, which was comprised of about 33% wealthy villas, 33% horrible slums, and 33% public areas, water to each could be controlled. In a drought, slums were cut off first, because people who lived there could go to the public areas, such as fountains and baths. Water to these areas could be reduced if the elite villas needed more. Thus the technology reinforced, and a very practical and evident way, the class structure of Rome. In rural areas, the huge rows of arches crossing the landscape reminded people that they were part of a huge empire, to which they owed their loyalty.

Aqueducts, and monumental Roman buildings, could be so large because of the use of concrete. Although not invented by the Romans, Roman concrete (a mix of quicklime, pozzolana ash and pumice stone) could be poured into forms and used as a core to support masonry.

Roman roads also tied the empire together, and were intended for moving troops quickly from place to place. (This is why we still find Roman roads under fields and rural areas - they were not built to connect towns or trade.) Originally the roads were made of wooden planks, on which troops could march and equipment could be rolled. But plank roads were subject to warping over time - they weathered badly. The Romans developed a sophisticated technique for building roads and streets, first digging out a trench, then layering it with different-sized gravel and stones, with large fitted stones on the surface. The roads were obviously intended to last forever, just like the Empire. Roman street

One major street innovation was standardization. In Roman towns, carts and wagons could clog the streets, so stepping stones were inserted across the streets at the corners. This made it possible for pedestrians to keep their feet clean crossing from sidewalk to sidewalk (another Roman invention). Since they were placed at set intervals, cart wheels had to go between them. The distance between stepping stones meant that all carts and wagons had to be the same size, and able to pass each other. This was a technological method for enforcing social habits, creating a better situation for all.

The ultimate Roman technology to me, though, is the geared waterwheel.

Might as well learn this now - I'm into waterwheels. And mills. And textile manufacturing. But that will come later!

Vitruvius is the font of information for historians on Roman waterwheels and many other constructions. He was a Roman officer and an engineer. His De Architectura is one of the few surviving written works on architecture from this time (it was rediscovered in 1414 by Renaissance collector Poggio Bracciolini). In his works, he drew and described technologies in use at the time, such as water clocks, cranes and catapults. We know about Greek technologies (such as Archimedes' screw) because he described them. And archaeology has helped us see how the mills worked:

Grist mill animation (www.riverlorian.com)
Descriptive text

Why was massive flour production so important? Because in addition to feeding the military, we have those slums. Roman cities had many slaves and many poor, who posed a continual threat to the order of the empire. Keeping them fed was part of what historians call "bread and circuses" - Rome providing basic food and entertainment to prevent revolt.

Ptolemy's Map

How did the Romans know their place in the world, and expand so confidently? Hellenistic mathematicians and geographers Eratosthenes (3rd century BC, 3-volume Geographica lost but pieced together in excerpts from other sources) and Claudius Ptolemy (AD 2nd century, work rediscovered in the late 13th century by Maximus Planudes) had developed sophisticated world maps. Eratosthenes correctly calculated the circumference of the earth and provided a map, dividing the world into polar, temperate and tropical zones. Ptolemy improved the projection and added current knowledge. Here are their maps, in 19th century versions:

Eratosthenes map Ptolemy's map

The Roman Empire declined in AD 5th century, having been subjected to poor leadership, barbarian migrations, and religious turmoil. The first of these, poor leadership, has a possible technological aspect, at least according to early 20th century historian Rudolf Kobert and popularized in 1965 by historian S.C. Gilfillan. Lead was a common element in the Roman world. It was used as a foundation for face makeup (to make skin white), a material for cups and tableware, and as a durable lining for water pipes. These uses meant that the wealthy Romans were the most exposed to lead. The cups in particular would have been a problem, since wine would cause the lead to leach out of the cup into the wine. In contrast, poorer people didn't wear makeup, used ceramic tableware, drank water from clay pipes, and tended to drink water or milk (an antidote for lead, as it happens) instead of expensive wine. The theory is that the elite class was slowly poisoned.

In 1984 historian John Scarborough pointed out that this theory had become popular as a replacement for that of Victorian historian Edward Gibbon, who had blamed the fall of the Empire on Christianity. I can certainly see why 1965 would be the time when it would be popular - during that time we were discovering the damage that man-made chemicals were doing to our environment and our health. So this is yet another example of how what historians look at varies according to the issues of their own time. While the lead-poisoning theory has been discredited in recent years, in the case of certain individuals (I'm thinking of a couple of particularly insane emperors), it may have been a factor. The popularity of the theory also shows the continuing disbelief that such a huge and well-organized empire as Rome could ever fall.

But fall it did, as Germanic peoples moved in to the Empire. This was a migration taking centuries, and in fact many Germanic tribes collaborated with Rome and protected the borders. But population pressure proved too great, as many groups pushed their way west due to climate factors in Asia. The culture they brought with them was quite different, and their technological achievements difficult to document. They tended to be rural farmers or hunters or woodspeople, living off the land. Terrified Roman sources tell us that they had no respect for concrete buildings, or engineering, or churches, or baths (or bathing, for that matter). They were mostly illiterate, and brought in an oral culture. Many Greek and Roman scientific works "disappeared" - some had been traded by Greek and Roman merchants to places eastward, some were acquired by the Church and were kept in monastic libraries, and some simply vanished. Those finding their way east were preserved in the eastern Roman Empire, which had always been primarily Greek and had separated from the west in the 4th century. This Byzantine Empire was ruled by a strong emperor with deep ties to the Christian Church, and the classical and Hellenistic tradition of scholarship could be said to have devolved to the Byzantine Empire for several centuries.

Empire map

Byzantium had its own technological innovations. The pendentive dome over the Hagia Sophia church (AD 2nd-3rd century) was another technological innovation. The technique of modeling a dome over a square space by cutting out a sphere would not be duplicated again in Europe until the Renaissance. They developed rafted grain mills that could be used on rivers and moved as needed, and counter-weighted trebuchets that were better than catapults. The infamous Greek fire, which was likely a pressurized fuel propellant flame-thrower on a large scale, was used in naval warfare. It was feared throughout the known world, and the chemical composition of the mixture was a state secret. Greek fire could also be sealed in pots for highly effective grenades.mosaic

Mosaics had been invented by the Greeks many centuries before, but in the late Roman Empire they took on different characteristics due to new methods. Although in Western Rome, mosaics were mostly created as floors in villas, in Byzantium they covered walls and ceilings because the use of mosaics was in churches, and you didn't want religious icons walked upon. Mosaics are made up of small pieces of colored substance. The earliest mosaics used colored stone, at first natural pebbles but by the Romans, engineered stone. In Byzantium, they began to import colored glass from Italy, and developed pastes made of glass, which allowed the light to dance through the mosaic. Mother of pearl, gold leaf, and silver added even more sparkle. Sponsored by the Christian state, mosaics got larger and more beautiful throughout Byzantium.

Abbasid mapDuring these centuries a new power arose in the east, Islam. In converting to the new religion in the 7th century, many commercial tribes in Arabia and beyond repeated a pattern of collaboration and adaptation for the sake of trade. The ongoing commercial contact between Arab traders and those in Mesopotamia, Egypt and the Hellenistic Empire meant that books, ideas and inventions diffused throughout the emerging Islamic Empire. By the 9th century, the cultural and scientific center of this empire was Baghdad, heart of the Abbasid Caliphate, where Persian and Arabic scholars pored over the works of classical Greece and Rome. Like the researchers at Alexandria centuries before, these scholars were funded by the state to engage in their research. Some historians believe that state funding leads to more "pure" research - abstract explorations into the natural world, without practical intent. That would be science rather than technology, even though the knowledge might later influence technology.

Islamic scholars thus studied and advanced classical knowledge. In medicine, they divided hospitals into wards to prevent cross-infection, and taught medical students in the hands-on environment. They engaged in advanced surgical techniques, inhalant herbs for pain and anesthesia, and the application of sulfur for skin complaints. Al-Rāzī (known as Rhazes in Europe) was one of the most famous physicians of the day. His De variolis et morbillis (A Treatise on the Smallpox and Measles) showed the difference between these two diseases, and his Kitāb al-ḥāwī, the “Comprehensive Book,” surveyed Greek, Syrian and early Arab medicine. His books contained not only factual information, but his own experiences as a physician.

Another Abbassid specialty was an improved astrolabe. We think astrolabes were used in ancient Greece, at least in a simpler design. And we know they were used in Europe in the Middle Ages, after improvements were made by the Arabs. View this 9-minute TED talk on the astrolabe, because it not only tells how an astrolabe works, but also what we've lost now that we don't use it.

Trouble viewing? See it on the TED Talk site.


Empires need vast resources to maintain them, but they also create vast resources. These cultural resources were funded by centralized states and merchants who can trade goods safely within their zones. They may include vast networks for moving armies, but they also can be cosmopolitan, recognizing and appreciating contributions from other cultures. Within such an environment, the collection of knowledge can be financed by empires with vision, who want to connect themselves to both the past and the future. Thus, when western Rome fell, Byzantium was able to preserve Roman as well as ancient Greek knowledge. And under the Abbasid caliphs it became apparent that a centralized state can provide good support for scientific endeavor - even today there is an appreciation that government is often the best benefactor for scientific experimentation and learning. With a longer view, it is possible to recognize the benefit of such sponsorship, beyond immediate profits.