During the period of the Caliphs the learned men of the Christians and the Jews were not only held in great esteem but were appointed to posts of great responsibility, and were promoted to the high ranking job in the government… He (Caliph Haroon Rasheed) never considered to which country a learned person belonged nor his faith and belief, but only his excellence in the field of learning.
Dr. William Draper
After the fall of the Western Roman Empire at the end of the 5th century, the western and central part of Europe was swept down by many barbarian tribes and fall into the so-called Dark Ages for some five centuries. During this time, the centers of the world’s art and science moved to the east—to the eastern Roman Empire, which managed to survive the attacks, China and India, where great civilizations grew and spread, and into the mighty Arabic empire. The period 9th-13th century was full of extraordinary activity in science and technology in the Arabic empire. In the 8th century, the Abbasid dynasty took over the rule of the vast Muslim world and moved the capital to the newly-founded city of Baghdad. Over the next five centuries, the city would become the world’s center of education and culture.
The Abbasid Caliphs were very interested in clocks and ingenious devices. There are many recorded contributions to the area of automatic machines from this period. The Arabic automata technology, as well as many other Arabic technologies, had as a basis the Greek automata tradition of mainly two engineers, namely Philon of Byzantion and Heron of Alexandria. Several Arabic scientists are known to have worked in the field of automata—Abu Musa Jabir ibn Hayyan from the 8th century, the so-called pseudo-Archimedes and Banu Musa brothers from the 9th century, Al-Muradi and Al-Khazini from the 11th century, Hibat Allah ibn al-Husayn and Ridwan Al-Khurasami from 12th century, and Al-Jazari from early 13th century.
Banu Musa brothers—Moḥammad, Aḥmad, and Ḥasan ibn Musa ibn Shakir, were Persian scholars who lived and worked in Baghdad in the 9th century, under caliph Al-Ma’mun and his successors, who recognized their abilities and enrolled them in the House of Wisdom, an institution created by him as a center for collecting, translating and studying books from other lands. Moḥammad was the most productive of the brothers, and he took a general interest in all the sciences, Ahmad was the engineer of the family, and Hasan was the geometer.
The works of the Banu Musa brothers encompass both translations and original contributions in the fields of geometry, astronomy, mechanics, and music. While they took Greek works as a starting point, they went well beyond anything achieved by Hero, Philo, and Archimedes. Their preoccupation with automatic controls distinguishes them from their Greek predecessors, including the Banu Musa’s use of self-operating valves, timing devices, delay systems, and other concepts of great ingenuity. They wrote almost 20 books, but only several survived to our time.
One of them, A Book on the Description of the Instrument Which Plays by Itself (al-Āla allatī tuzammir bi-nafsihā), written about 850 CE, describes the first music sequencer, an example of an early type of programmable machine. The instrument is a mechanical hydraulic organ that operates automatically by the action of weight and water pressure. The air pushed by the hydraulic pump is compressed in a sphere to power a flute with nine holes. The holes are opened and closed by eight levers, the ends of which make contact with the fixed raised pins arranged on the lateral surface of a revolving cylinder so as to produce a well-known melody.
The Banu Musa even proposed a mechanism of an automated flutist, an embryonic stadium of the first musical humanoid automaton:
If we want to create a humanoid flutist, we simply have to incorporate the whole device in the body of the statue, fix the flute in its mouth and disguise the levers as fingers and adapt it to his arms. Furthermore, we have to bend back these levers inside the body of the statue so that they reach the pins fixed on the revolving cylinder. Finally, we put in place the air conduits in the body of the statue and direct them towards the mouth of the flute. We can also hide the entire mechanism so that only the flutist who is playing can be seen.
Another book by the brothers, Kitab al-Hiyal al-Naficah (“The Book of Ingenious Devices”), written about 830 CE, the only surviving work by Aḥmad, describes 100 inventions. Some of the devices described in the book were inspired by the works of Hero of Alexandria and Philo of Byzantium, as well as ancient Persian, Chinese, and Indian engineers. Most of the devices described in the book, however, were original inventions by the Banu Musa brothers. The list of devices includes beakers, pitchers, jars, basins, troughs, boilers, whistles, pipettes, flasks, fountains, lamps, bellows, a dispenser, and a grab.
Let’s examine Model 97 from The Book of Ingenious Devices, describing a lamp, known as “the lamp of the God” (see the lower drawing). It features a wick that comes out by itself and the oil flows by itself and everyone who sees it thinks the fire has consumed nothing whatsoever from the oil and from the wick.
The pulley (k) which is in it for the chain to be passed over it, and the weight (s) to which one end of the chain is fixed. We position the pipe into which the air passes from the lamp into the oil reservoir in the column (jb). The chain goes through into the hollow of this pipe. And we install another small pulley (h) above the top of the pipe and lead over it the chain in the way we have illustrated so that chain terminates, as we have illustrated, at a float (t). Float (t) should be double the weight of weight (s), although the float rides above the oil. Between the reservoir containing the oil and the lamp, we make another hole (a) like hole (j) and we lead out from hole (a) and pipe (ae) that terminates at the mouth of the bird. The bird’s beak should be above the hole (f) in the lamp so that when the oil flows through pipe (ae) it discharges into hole (f) and enters the lamp. It should be clear that when we pour the oil into the hole (l) it enters pipe (ls) and flows through pipe (wz) into the reservoirs in which the pipe is. Float (t) rises, weight (s) sinks, and in sinking pulls the chain, which rotates pulley (k), and the toothed wheel (y) rotates with it. Toothed wheel (mx) slides, together with the wick in direction (x). We pour the required amount of oil, the lamp (fb) fills with oil, and we light the wick while we are observed. The oil diminishes until hole (j) is uncovered and the air enters the reservoir through hole (j) and the oil runs from the reservoir into the lamp through pipe (ae), and the oil drips from the bird’s beak until the end (j) of the pipe is closed. When the oil diminishes in the reservoir, float (t) sinks, pulling the chain, weight (s) rises, pulley (k) and toothed wheel (y) rotates, and the rod to which we attached the wick moves in the direction of the mark (x) and the wick therefore emerges.