Jabir ibn Hayyan

The previous post mentioned the man who discovered the combination of chemicals that dissolved gold. He could not have done that haphazardly; he had to have gained extensive knowledge of chemicals first. As it turns out, his works include the oldest known system for classifying chemicals.

His name was Abū Mūsā Jābir ibn Ḥayyān, and he lived in the 8th century...we think. To be fair, he does not get mentioned until the 10th century by a  Baghdad bibliographer who said Hayyan was a disciple of the Shi'ite Imam Ja'far al-Sādiq (who died in 765; Haiyan's writings refer to al-Sādiq as "my master"). That biographer assured his audience that Jabir existed, and made a list of his works, although many later Shi'ite biographers never mentioned Hayyan, and it is considered unlikely that he wrote the many hundreds of texts attributed to him.

Someone had to create the writings attributed to Hayyan, however, and perhaps the name was a pseudonym used to avoid the potential negative publicity because it looked like alchemy, which was rejected by many. Also, the works attributed to him are so many and varied that it is difficult to believe they were the work of one man. He may have inspired a "workshop" of students and followers who produced many of the works. Despite the confusion about his existence, a 271-page biography was written in the 20th century, and is readable at the Library of Congress website (if you can read Arabic, that is).

The body of work includes many techniques that are familiar to any high school student who has taken Chemistry: precipitation, crystallization, and distillation. It also teaches procedures for making apparatus (see the illustration) and equipment, for improving the quality of products such as steel, and how to reduce oxidation in metals. We learn from them how to dye and waterproof cotton and leather, the purification of gold, and how to treat cinnabar to extract pure mercury.

You may notice, in large sheets of glass used for, say, store fronts, that there is a greenish hue (most visible if you look at the edge of the glass sheet). Hayyan's writings explain how manganese oxide can be added to glass production to eliminate the greenish hue, resulting in a perfectly clear pane. These writings provide most of what is known about chemical analysis until the 16th century.

I want to go back to the question of Haiyan's identification. One of his writings implies an association with a certain family, the Barmakids. His 10th century biographer, Ibn al-Nadīm (c. 932–995), reports that Hayyan was devoted to Jaʿfar ibn Yaḥyā al-Barmakī, an Abbasid vizier. You may not recognize that name, but I promise you that you have heard of him. In fact, I promise 1001% that you have heard of him. With that teaser/clue, I'll see you tomorrow.

The Hourglass

Detail, Allegory of Good Government
Ambrogio Lorenzetti, 1338

The hourglass has become a symbol of medieval technology, one of our first attempts to quantify and measure time. We know it existed in the 14th century, from a 1338 fresco by Ambrogio Lorenzetti (c.1290 - 1348) in which the allegorical figure of Temperance holds one (Temperance, after all, is about taking a "measured" response to something, rather than uncontrolled actions). In 1345, an English merchant's receipts show that he paid for "twelve glass horologes" in Flanders, establishing that they were probably already prevalent and in demand.

Sailors found the sand-filled hourglass a definite improvement over its predecessor, the clepsydra* (the water clock), which was affected too much by the swaying of the ocean. When Magellan (c.1480 - 1521) circumnavigated the globe, his fleet had 18 hourglasses per ship, with a page dedicated to turning each one to keep accurate time.

They were also preferable in the early Middle Ages to clocks, because they did not rely on complicated and delicate machinery that needed frequent maintenance.

Where and when was the hourglass invented? A story that it was invented in the 800s by a monk at Chartres named Liutprand has no evidence to support it. The clue to the origin may be in the construction. The earliest hourglasses used marble dust for the sand. Also, the hourglass required expertise in glass-blowing. The likeliest location for these two features of the hourglass to be brought together is Italy, particularly Venice, where glass-blowing was a highly developed art and marble was readily available.

By the end of the 14th century, hourglasses were so common that the Goodman of Paris, writing a guidebook for his young wife in the 1390s, included a recipe for preparing the sand/dust for an hourglass:

Take the grease which comes from the sawdust of marble when those great tombs of black marble be sawn, then boil it well in wine like a piece of meat and skim it, and then set it out to dry in the sun; and boil, skim and dry nine times; and thus it will be good.

Not only must the hourglass have become common, but its construction was clearly something that could be contributed to by a regular household.

*clepsydra is from the Greek and means "water thief"; they could be very elaborate, but were naturally susceptible to humidity and temperature.

Æther or...

[I am on a brief vacation, so here is a post from the past. This post first appeared 25 August 2012.]

Speaking of æther...*

In Greek mythology, Æther was the offspring of Erebus (deep shadow) and Nyx (night). Despite springing from dark parents, the word is related to the verb that means "to incinerate";** "æther" was used to refer to pure fresh air, something more pure than ordinary air; in fact, a pure air that was breathed by the gods.

Plato's Timæus (which was very popular for medieval scholars, as I've mentioned before) and his student Aristotle both considered æther crucial to the structure of the universe. Aristotle called it the "fifth element" and described its superiority over earth, air, fire and water because it did not have their limiting properties (hot or cold, wet or dry) and was unchangeable. It was also called quintessence which means "fifth essence/element."

The Greek philosopher Plotinus (c.205-270) taught that there was a supreme "One" that existed prior to all created things, was synonymous with "Good" and "Beauty," and was like a light shining in a void. To the medieval Christian mind, Plotinus was describing God, and therefore was one of those non-Christian philosophers worth listening to. Plotinus said æther was immaterial and could be moved through; he also said there was no such thing as empty space.

Small wonder then that the Middle Ages filled the area above the earthly atmosphere, the space through which the celestial spheres rotated and planets and stars moved, with æther. Æther could not be disproved, and the vacuum of space was as difficult to imagine for the Middle Ages and later as "zero" was for the Romans earlier. The 17th century philosopher Robert Fludd fused Plotinus and Genesis when he explained:

The middle region of the universe, created on the second day, has various names because of the action of the light-stuff as it extended downwards; for, taken by itself, with regard to its own particular material, it is called the Middle Spirit, after the dispersal of darkness: compared to the upper sky, that is, to light-stuff, or mixture of light-stuff and spirit, it is called Ether... [Robert Fludd, The Technical, Physical and Metaphysical History of the Macrocosm and Microcosm, 1617-1624]

The scientific theories were there for all to read and understand.

To be totally honest, the "ether" being tested for in the Michelson-Morley experiment was not conceptually the same æther discussed so extensively in classical and medieval times, but the descent from one to the other clearly runs through the philosophical writings of Western Civilization. Æther was here to stay, until modern technology could eliminate it from our worldview.

*With a nod to Brian Koberlein (on Google +) for shamelessly stealing this idea and his title.
**The name Æthiopia was coined because the inhabitants were black-skinned, as if burnt by the sun.

Gravity

Climbing Lucifer in Dante's Inferno

A long time ago (it seems) I touched on gravity and said "there was no working theory of gravity yet; just a feeling that substances could be heavier or lighter." Theories of gravity did not need Newton to become useful to understanding the world.

Still, if the inhabitants of this globe knew it was a globe, they had to come to terms with how things stayed on it. John Mandeville wrote a book of travels in the 14th century in which he addresses this issue:

from what part of the earth that men dwell, either above or beneath, it seemeth always to them that dwell that they go more right than any other folk. And right as it seemeth to us that they be under us, right so it seemeth to them that we be under them. [Mandeville, Voyage and Travels, chapter xx]

The Middle Ages understood that objects inclined toward the earth itself, wherever they were upon its spherical surface. In fact, gravity was sometimes described as "kindly inclining."

Dante (1265-1321) in his Inferno has his traveler and guide (Virgil) descend through the levels of Hell—not a metaphorical journey, but descending deeper and deeper below the surface of the Earth—finally reaching the gigantic body of Lucifer embedded in the ice. They start climbing down his body when, at his groin region (the bottom-most part of the world), down becomes up, and they have to reverse their orientation. They are now climbing up to his feet.

Was Dante just speaking metaphorically? Did he understand gravity as it operates at the center of the Earth?

Maybe he did. Vincent of Beauvais (c.1190 - 1264) wrote an encyclopedia that was very popular in the Middle Ages. It is not unexpected that Dante would have been very familiar with it. Vincent was well aware of the spheroid nature of the Earth, and that objects fell directly to Earth no matter where they were on the surface. In his Speculum Naturale ["Mirror of Nature"], he explains as much of the world as he can in 3,718 chapters spread across 32 books. In Book vi, he tells the curious what would happen to a stone dropped into a hole that goes straight through the globe to the other side. He says that it would not fight gravity and rise to the other side, but would stay at the center.

The acceptance of a terrestrial globe forced scholars and philosophers to re-think the action of falling bodies and their relationship to the Earth. Common sense led them to arrive at the proper effects of gravity, even if they did not have the science or mathematics to understand the cause of gravity.

Making Parchment

The term parchment is often applied to any animal skin used for writing on, but historically it was used for sheep or goat skin. Cow or calf skin was also used, but was turned into vellum. Very fine vellum came from very young calves, or even still-born calves. These pages were smaller than the pages that could be made from adult animals.

Although vellum is from the same word as calf, Latin vitellus, parchment has nothing to do with the material. It derives from Pergamum, where it is said parchment was invented during a dearth of the export of papyrus out of Alexandria.* According to Pliny (27-79 BCE), this was under King Eumenes; he does not distinguish, however, if this was Eumenes I (263-241 BCE) or Eumenes II (197-158 BCE).

The person who turned animal skins into parchment in the Middle Ages was called a parchmenter. The parchmenter needed to pick skins carefully. The hair of the animal was a consideration, since the skin below would match it. Black-furred animals would yield darker parchment, less suitable for writing on.

Making parchment in the Middle Ages was fairly straightforward. The skin was placed in cold water for at least a day to clean off any blood and dirt. A lime solution was next, to eliminate the hair. For a week, the skins would be stirred with long wooden poles a few times each day. After the lime bath, they would be stretched on a wooden frame, with thread or leather thongs attached through numerous holes around the edge to ensure that it stretched and dried flat. The skin would be scraped with a curved blade to remove any remaining hair. The occasional oval hole seen in parchments was not the result of bookworms. Imperfections from tick bites in the living animal produced holes in the skins that would expand during the stretching and drying process.

Scraping the parchment was an ongoing process. By the 12th century, scraping skins to tissue thinness was common. Extensive rubbing with chalk and pumice helped produce a smooth surface that would take ink without spreading through the imperfections in the surface.

After the treatment, it was removed from the frame. It was soft and supple enough to roll up until needed, when it was cut into sheets that were usually sold by the dozen.

*Supposedly, Alexandria was using so much of the papyrus reed that it was being over-harvested; they simply could not afford to export any.

Medieval Meteors

Woodcut showing meteorite coming to Ensisheim.

Today is the anniversary of the first meteorite the exact date of whose fall to Earth has been recorded. It was in 1492, around noon, when a young boy heard an explosion and observed a rock fall from the sky, burying itself in a wheat field outside the town of Ensisheim in what is now France (but was then Austria). The sound of the explosion was heard up to 150 kilometers away. Townspeople came to investigate and found a 127-kilogram triangular rock in a pit a meter deep. They retrieved it from its trench and immediately started chipping pieces from it, until a local authority stopped them, ordering the rock to be delivered to the steps of the local church and preserved pending an investigation.

But that was far from the first meteor or meteorite recorded.* The Journal for the History of Astronomy in 1978 published "Meteors, Meteor Showers and Meteorites in the Middle Ages: From European Medieval Sources." The article lists every meteoritic phenomenon it could find by carefully scouring historical texts, and includes items such as:

453 or 454 — Tres magni lapides (three big stones). Three meteorites fell in Thrace 

518 — Alius ignis . . . instar scintillarum (another fire sparklike). A meteor. Date uncertain. Theophanis Chronographia 

557 — Discursus stellarum (moving stars). A shower lasting the whole night that caused terror. Date uncertain. G. Cedrenus

There are several pages of entries. Meteoric phenomena could be seen as good or evil, often depending upon their proximity to events in the lives of the observers.

As for the Ensisheim Meteor, it currently resides in the Ensisheim museum and is toasted every year by The Brotherhood of Saint-Georges of the Guardians of the Meteorite of Ensisheim. Maximilian I (1459-1519), son of Holy Roman Emperor Frederick III, visited the rock shortly after its fall and declared it a wonder from Heaven. He took some chips for himself and a friend. After years of people taking parts of it away, the rock is now roughly spherical and has been reduced to about 56 kilograms. I guess everyone wanted to have their little piece of Heaven.

*A meteor (first coined in the 16th century, from a Greek word meaning "lofty") is a rocky object that streaks through the atmosphere, heating up via friction and creating a streak of light; a meteorite is a meteor that reaches the ground. A small percentage of meteorites are composed of nickel and iron.

Anthemius of Tralles

Anthemius of Tralles (c.474-c.557) was mentioned as one of the builders (along with Isidore of Miletus) of the new Hagia Sophia. We know much more about him than that, however, both about his talents...and his annoying pranks.

We have an anecdote about how he avenged himself on his neighbor, Zenon, by fashioning leather tubes that he ran to the joists of an upper room of Zenon's house, where Zeno used to entertain guests. We are told that Anthemius would, by running steam through the tube, create loud noises and vibration in he room, frightening the guests into thinking there was an earthquake. Also, he would flash incredibly bright light into Zenon's eyes with a concave mirror.

Possible? Well, he did write a treatise "On burning-glasses"; we don't have the treatise anymore, but enough of it existed in 1777 to be included in a work called Concerning wondrous machines by an L. Dupuy. He apparently studied and wrote on properties of mirrors and lenses, and supposedly described a camera obscura. He explained how to construct an ellipse using string, and he wrote a book on conic sections.

This intellectual excellence ran in the family. His father, Stephanus of Tralles, was a physician with five sons. Two of them followed in their father's footsteps, Dioscorus staying in Tralles and Alexander finding fame in Rome.  The rest pursued different professions. Metrodorus became a grammarian in Constantinople; Olympius became an expert in Roman jurisprudence.

Anthemius' knowledge of conic sections and parabolas would have supported both his work on optics (known to the later "Second Ptolemy" Alhazen ibn al-Haytham) and his architectural aspirations when designing the dome of the new Hagia Sophia. He was able to create what is called a "pendentive": a design that allows a dome to be built onto a square base.

His success with Hagia Sophia led to him being also chosen—probably by Emperor Justinian—to design flood defenses at Dara in northern Mesopotamia.

The Flying Monk

Did a monk of the 11th century accomplish the first manned flight? There is reason to believe so.

In the Gesta Regum Anglorum [Deeds of the English Kings] of William of Malmesbury, we read of a monk named Eilmer in Malmesbury Abbey who launched himself from the Abbey's tower with a set of home-made wings. According to the story, he glided more than a furlong (a furlong is 220 yards, or just over 200 meters). Then, suddenly realizing how precarious his position was, he panicked, lost control, and crashed, breaking both legs. He had extreme difficulty walking for the rest of his life.

How likely is this story to be true? Let's first consider what we might call "incidental" evidence. William is not just reporting a legend: although he lived after Eilmer, he was in the same Abbey, and very likely got the story from elders who knew Eilmer and had witnessed the experiment first-hand.

William also records a curious detail: that Eilmer ever after claimed his failure was due to not constructing a tail for his device. This suggests that Eilmer really did study birds in flight, and realized that a tail is also important to steer and brake for landing. Unfortunately for the history of manned flight, the abbot forbade him or anyone from repeating the crippling experience.

But was such a flight possible? Several historians have weighed in, and even the United States Air Force is willing to accept it. The conditions that make it believable are as follows:

The Abbey was situated at a cliff edge over the Avon River that would have created strong updrafts. Eilmer would have seen how jackdaws use the strong updraft to glide and soar without the need to flap. The tower would have been about 80 feet high, giving him additional altitude for catching an updraft. If Eilmer were a small man, calculations suggest that a light and strong frame of willow or ash, covered with parchment or light cloth, would only need an area of 100 square feet to support his weight. William says the wings were attached to Eilmer's hands as well as feet—this supports the notion that they covered a larger area than just wings attached to arms.

Local legend says his landing spot is an area now called "Oliver's Lane." (Ralph Higden's Polychronicon—mentioned here—erroneously referred to Eilmer as Oliver, and the name stuck.) Given the constant wind conditions and the distance he is supposed to have flown, Oliver's Lane is precisely where modern calculations based on wind currents place his likely landing spot. The gliding flight would have lasted about 15 seconds.

He lived a long time afterward, becoming known for scholarship. His writing on astronomy existed and was well-known into the 16th century, but has been lost since. Also lost to history is the tavern "The Flying Monk" in Malmesbury, which has since been replaced by a shopping center.

Asking Questions

Image from Adelard's translation
of Euclid's Elements of Geometry

Being inquisitive is the first step to learning.* In the early Middle Ages, the presence of many classical authorities circulating in Latin, such as Aristotle and Plato, eliminated the need for inquiry in the opinions of many.

The 12th century saw an influx of more works, many of them Greek writings (preserved by Arabs) or Arab writings. The widening of philosophical and scientific horizons by this wave of knowledge caused many scholars to re-think what had been established.

Adelard of Bath (c.1080-c.1152) was an English philosopher who was in a position to translate into Latin for the first time many of the Greek and Arabic works becoming available to the West. After studying at Tours and teaching at Laon in France, he traveled for seven years through Italy, Sicily, Syria and Palestine. He translated Al-Kwarizmi's astronomical tables and Euclid's Elements of Geometry from Arabic, wrote works on the abacus and on his love of philosophy, and a book called Questiones Naturales (Natural Questions) in which he tackled, in dialogue form, 76 questions about the world. One of his themes is the choice of using reason rather than merely accepting authority.

For what should we call authority but a halter? Indeed, just as brute animals are led about by a halter wherever you please, and are not told where or why, but see the rope by which they are held and follow it alone, thus the authority of writers leads many of you, caught and bound by animal-like credulity, into danger. Whence some men, usurping the name of authority for themselves, have employed great license in writing, to such an extent that they do not hesitate to present the false as true to such animal-like men. [...] For they do not understand that reason has been given to each person so that he might discern the true from the false. [Questiones Naturales, VI]

To be clear: Adelard's science is not ideal: his periodic table of elements contains only four substances, which are mixed in various proportions to create all materials. Some animals see better by day or night because of either white or dark humor in their eyes. We see because an extremely light substance (Plato's "fiery force") is created in the brain, gets out of the brain through the two eyes, swiftly reaches an object and learns and retains its shape, then returns to the brain through our eyes so that we "see" what is in front of us. A mirror, whose surface is smooth, bounces back the fiery force, which on returning to us picks up our image on its way and allows us to see our reflection.

Still, his works were copied and distributed, and influenced much of what was to come. His assertion of reason over blind acceptance of classical authorities was an important milestone in scientific thought. Many of his ideas are seen again in the writings of Robert Grosseteste, Roger Bacon, and Hugh of St. Victor. Once the printing press was perfected, Adelard's translation of Euclid became a standard text for a hundred years.


*One of the followers of this blog is part of a group trying to promote inquiry-based learning in young people. Visit Prove Your World to learn more.

Figuring out the Sun

[DailyMedieval is on semi-hiatus for the holidays, and I am re-cycling some older posts. For Christmas I received A Short History of Nearly Everything by Bill Bryson. I have just read the section on the brilliant Lord Kelvin, who estimated the age of the Earth at as high as 400 million years. Interestingly, he kept revising his estimate, from 400 million to 100 million to 50 million and, finally, to 24 million. The difficulty in adhering to his longer estimates, for him and others in the burgeoning field of geology, was not that they could not imagine the Earth being older, but that for the Earth to be that old, the Sun would have to be around—and their best estimates of how the Sun worked could not imagine the nuclear forces that would allow it to produce heat continuously for hundreds of millions of years. This reminded me of the post for 10 June 2012.]

How Does the Sun Work?

Robert Grosseteste (c.1175-1235) is considered by some to be the founder of modern English intellectualism. Among other topics, he focused (pun intended) on light. One of his works sought to explain how the sun produced heat.

He first explained the three methods of heat generation:

1. An object that is hot
2. Motion/Friction
3. The scattering of rays

He determined that Method 1 cannot apply here. For heat to transfer from a hot object, there must be a medium through which it travels, and that medium will heat up during the transfer of heat. Clearly everything between the sun and us does not heat up.

He decided that Method 2 was also insufficient to explain the heat, because the motion that creates heat is caused by two substances moving in opposite directions—for instance, rubbing your hands together to warm them up—and the sun's circular motion does not act upon a second substance moving in an opposite direction: everything up there moved from east to west.

Method 3, he decided, must pertain. He reminds his reader that Euclid explained how a concave mirror can focus the sun's rays to cause a fire. He stated that the sun's rays falling upon the earth are scattered, but reflection by a mirror or refraction by a (clear) spherical body can change the direction of the rays, focusing them via the medium of the dense air and generating heat. For him, this had much to do with the denseness of the medium: he stated that the same amount of light falls on a mountaintop and scattering can be observed there, but the thinness of the medium of air disallows the generation of heat.

Avicenna

In 1527, when the healer and alchemist Paracelsus wanted to display his contempt for tradition, he burned a book in the town square in Basle, where he had been appointed to the university by the town council. That book, allegedly, was The Canon of Medicine by Avicenna. Paracelsus had gone too far in rejecting what was still considered a fundamental work in western medicine. He was ejected from his post at the University, and from the town itself. Avicenna was too respected, even 500 years after he wrote his books.

Abū ʿAlī al-Ḥusayn ibn ʿAbd Allāh ibn Sīnā, called by the West Avicenna (c.980-1037), was mentioned here in the context of medicine. About 40 of the 240 surviving texts that he wrote (of a total of about 450!) deal with medicine. The encyclopedic Book of Healing and the Canon became standard textbooks for centuries.

The Canon assembled the best known medical knowledge to date, including Galen (129-c.200 CE) and Hippocrates (c.460-c.370 BCE) and adding a great deal of information that seems new to Avicenna. For instance:

The 'Qanun' is an immense encyclopedia of medicine. It contains some of the most illuminating thoughts pertaining to distinction of mediastinitis from pleurisy; contagious nature of phthisis*; distribution of diseases by water and soil; careful description of skin troubles; of sexual diseases and perversions; of nervous ailments. [George Sarton, Introduction to the History of Science]

Another reason why Paracelsus would want to burn Avicenna: Paracelsus was advertising his reputation as an alchemist, and believed that with salt, sulphur and mercury you should be able to produce anything. Avicenna, however, was completely opposed to the idea of alchemy, rejecting the notion that man could improve on Nature.

One could still work with Nature, however. Besides dealing with disease and injury (such as explaining how to judge how much healthy tissue could be removed during an amputation or the removal of cancerous tumors), Avicenna promoted restoring health, not just treating disease. He believed in the importance of physical exercise, of a good diet, and of a healthful environment.

Among other innovations, he lays the groundwork for modern ophthalmology, even suggesting that the optic nerves cross over each other. He laid out careful ground rules for the preparation, administration, and testing of drugs.

It has been called "one of the most significant intellectual phenomena of all times."** The Canon of Medicine is an essential part of any curriculum that studies the history of medicine.

*tuberculosis
**Swiss tuberculosis expert, Arnold Klebs

The Rotating Earth

Nicholas Oresme

While re-examining Aristotle, Jean Buridan used observation and brainpower to anticipate some of the ideas we attribute to Galileo and Newton. He carried his ideas further when he put his mind to the question of the Earth's movement.

For most scholars of the Classical and early Medieval eras, the Earth was fixed, and the Heavens rotated around the Earth once each day. Buridan didn't like this: the Heavens are so much larger than the Earth; why would God design such an inelegant system? Moving the Earth would be easier.

Ptolemy knew this could not be, because if the Earth were rotating, there would be a constant rushing of wind as the air of the atmosphere passed over the land underneath it. Buridan scoffed at this: the atmosphere would be rotating just as the land does. There was no reason to dismiss the idea that Earth rotated daily.

For Buridan, however, empirical evidence was crucial. Of course, his predecessors argued, the Earth clearly does not move; we can see that. Buridan, however, likened the situation to being in a boat on a river. An observer on a second boat that was tied to the bank would see the first boat moving, but if the observer on the second boat could not see the surrounding landscape, then he would not know which of the boats were moving. The problem, Buridan knew, was that without an outside frame of reference, one cannot tell if it is the Earth or the Heavens that is moving. He needed an experiment, and he thought of one.

...and that's when he made his mistake.

Here was his idea: shoot an arrow straight up above your head. If it comes back down where you are standing, then the Earth is stationary. If the Earth rotated under it, then the arrow would come down somewhere off to the side.

He didn't realize that the same property that moves the atmosphere along with the ground would carry the arrow along as well. It would be Buridan's most brilliant student, Nicholas Oresme (c.1325-1382), who would realize and state that the arrow moves along with the Earth and atmosphere. Lacking a way to definitively prove his ideas, however, Oresme would ultimately fall back on the Bible for guidance on this issue.

Defeating Eternity

How long has the universe existed? Has it been around forever? Did it have a beginning? Could it have a beginning? These questions troubled the ancients.

Aristotle in his Physics tried to answer this through reason. Everything that comes into being does so from something that already exists; matter is made from matter, after all. The matter of the universe would have to come into being from some underlying matter; it couldn't come from nothing. For the matter of the universe to come into being, some matter must have existed before it. This statement is ridiculously self-contradictory, and therefore could not be taken seriously. The universe must have always existed.

Others supported Aristotle. Critolaus (c.200-c.118 BCE) couldn't believe that human beings would ever stop simply procreating into eternity. In the Early Medieval Period, Proclus (412-485) produced De Æternitate Mundi (On the Eternity of the World) with 18 proofs.

This belief was about to collide headlong with Christianity, however. The Bible makes it clear that there was a moment of Creation. That being the case, the universe cannot have been eternal.

John Philoponus (490-570) was a prolific and controversial writer who realized that Aristotle needed to be questioned on some things. Although he would be condemned after his death as heretical for interpreting the Trinity as three gods instead of one God, he was known in his lifetime for defending the Biblical necessity of a universe with a starting point. He wrote "Against Proclus" in which he challenged every one of Proclus' arguments. The basis for his argument is simple, and referred to now as the Traversal of the Infinite. If the existence of something relies on the existence of something else prior to it, then you need to account for the existence of the prior thing. That prior thing would rely on the existence of something before that, and so on. You have to have an infinite series of assumptions that something existed before the thing that came afterward, and never actually explain where any of the substances came from. The world could not possibly be infinite, and must have been created by a divine being.

The Ring of Fire vs. The Flood

15th century portrayal of Ptolemy's map

Prior to the Age of Exploration, human beings in the western hemisphere did not attempt to travel long distances by sea and discover distant lands.* This was partially because ships that could handle a very long voyage were not able to be built or provisioned easily for such a journey.** Another reason is that the world was "known" to be shaped so that long voyages were fruitless.

Eratosthenes (c.276-c.195 BCE) had established in the Classical Era the spherical nature of the Earth through simple and clear experimentation; no one disputed that. (His math on Earth's diameter was probably a little off: the unit of measurement he used probably gave him an Earth 4000 miles larger around than it is.) What was up for debate was the question of what existed "over the horizon."

Aristotle (384-322 BCE), upon whose scholarly shoulders the Middle Ages tried to stand, loved symmetry. It made sense to him that there were five zones (from the Greek word meaning "girdle") around the Earth. The extreme top and bottom were icy cold and uninhabitable. Just inside of them were the temperate zones where humans and animals lived—note: he believed both temperate zones were inhabited. In the middle it was so hot—and clearly, the further south you go from Greece and the Mediterranean the hotter it got—that it was uninhabitable. Pliny (23-79) said that this central zone was so hot that it was actually a ring of fire and was unlivable and impassable, so we would never be able to visit the people living in the southern hemisphere.

Wait, said Christianity. That can't be. The Flood covered the whole world, and when the waters receded, the Ark of Noah came to rest on Mt. Ararat in Turkey, from which all the animals strolled away and repopulated the world. If the ring of fire at the equator is impassable, how can there be animals living beyond it? Worse, if there are people living in the southern temperate region, how are we going to reach them with the Word of God?

Proving that classical scholars did not always agree, Ptolemy presented different problems in geography. His Geography was translated and made available to Western Europe in 1406. His map (depicted above in a 15th century version printed in Ulm) showed that all you had to do was sail far enough south to reach the southern lands in the world, but he also extended the bottom of Africa eastward, enclosing the Indian Ocean. This meant you could not sail to the Indian Ocean and therefore to India, but would forever have to use the Silk Road (and incidentally pay tolls at every border crossing, something sailors get to avoid).

The Age of Exploration changed all this. In 1473, Aristotle was proved wrong with a Portuguese ship exploring the west coast of Africa passed south of the Equator. In 1488, another Portuguese ship sailed around the Cape of Good Hope and reached the Indian Ocean. India and the east were accessible by ship after all, and the Portuguese quickly established those shipping routes.

Ptolemy's Geography was erroneous in another way. He estimated the Earth's circumference at thousands of miles smaller than Eratosthenes. Since no one cared to duplicate Eratosthenes' experiments and determine the distances involved, Ptolemy might have been taken as truth by some. His estimates of the size of a spherical Earth would put Asia thousands of miles closer to Europe by sailing west. With Portugal dominating southern routes to the East, was it Ptolemy's miscalculation that prompted Spain's Columbus to try a bold plan to establish a different and (he thought) shorter route?

*Perhaps some day we'll get to some of the rare cases of accidental discovery of previously unanticipated lands.
**I have been aboard replicas of Columbus' ships; they are frighteningly small considering the journey they made.

Pre-Inertia

Expositio & questiones manuscript

Jean Buridan (c.1300-c.1361) was a University of Paris scholar who was not afraid to tackle some of the big scientific and philosophical issues of the day. That meant, in some cases, taking a critical look at one of the most revered figures in science and philosophy, Aristotle. Buridan, like William of Ockham (c.1288-c.1348),  believed in the observable reality around him, and believed that observation of the world was the key to understanding it. Challenging Aristotle could be risky, but as more and more scholars observed the world around them, they realized that Aristotle's theories needed amendment. He wrote Expositio & questiones (Expoition and questions) to analyze Aristotle's work.

For example, Aristotle believed that an object set in motion—let's say, a rock thrown by a human hand—continues to move after it has left the hand because there must be some continuous external force exerted on it. He theorized that, in the same way a hand swished through water creates little eddies and swirls in the water around it, so the rock's movement is continued by eddies and currents of the air. If there were no movement in the medium that helped carry the rock forward, he believed, the rock would stop its forward course (and presumable drop the the ground). The currents eventually faded, allowing the rock to end its forward flight.

Buridan was not satisfied with this. Building on the work of others (such as John Philoponus and Avicenna, both of whom deserve their own entries some day), he believed that there must be a property in the rock itself that accounts for its action once it has left the motive force of the hand. He called this property of the object impetus (from Latin impetere, literally "to rush toward, to attack").

The property or quality of impetus was clearly changeable. To hurl a heavy rock required you to give it more impetus than to hurl a pebble. Also, impetus was obviously used up over time, allowing the rock to cease its movement and fall. He also explained that a falling object gained impetus the longer it fell (are you paying attention, Galileo?). Unlike Aristotle, who believed that the medium of air in which the object moves helps it along, Buridan saw the air as resistance, causing the object to use up its impetus.

He expanded this theory by looking up. A question had bothered some philosophers for ages: why don't the planets slow down? Will they move forever? Buridan extrapolated his theory to say that a thrown rock in a vacuum would experience no resistance and its impetus would last indefinitely. If the planets were moving in a vacuum...

Well, actually, he couldn't go that far. He agreed with Aristotle that a vacuum couldn't exist in space, since there was no container to keep matter from rushing into the empty area. If above our atmosphere were filled with quintessence, however, Aristotle's "fifth element" that was pure, unchangeable, and frictionless, then the impetus imparted to the planets by whatever initial agency would continue to move forever! The idea of an eternal universe was supportable by science!

Doctor Profundus

I have written about the Oxford Calculators, four men at Oxford University in the second quarter of the 14th century who made great strides in science and philosophy by treating things like heat and light as if they were quantifiable, even though they did not have ways to measure them. They engaged in "thought experiments" and used mathematics to determine the validity of their points. They were not always right in the end, but they were meticulous in their approach. One of the four was so esteemed that he was called Doctor Profundus, the "Profound Doctor."

Thomas Bradwardine (c.1290-1349) had a reputation as a precocious student at Balliol College. We know he was there by 1321, and later took a doctor of divinity degree. A gifted scholar and theologian, he wrote theories on the Liar Paradox and other logical "insolubles." The Liar Paradox is the statement "I am a liar." For it to be true, the speaker must be a liar; but if it is a true statement then the speaker is not lying. Resolving with logic how such statements can be understood had been tackled for centuries. Bradwardine's work Insolubilia presented complex solutions for puzzles/statements like this.

Like many university men of his day, Bradwardine followed an ecclesiastical career path. After serving as chancellor of the university, he became chancellor of the diocese of London and Dean of St.Paul's. He was also chosen to be chaplain and confessor to Edward III (mentioned in this blog numerous times), celebrating victory masses after campaigns of the Hundred Years War and being entrusted with diplomatic missions. The only time he did not have Edward's support was when John Stratford, Archbishop of Canterbury, died. Bradwardine was elected archbishop by the canons of Canterbury, but Edward opposed the choice, preferring his own chancellor at the time, John de Ufford. When de Ufford died of the Black Death (this was in 1349), Edward allowed Bradwardine to assume the position. Bradwardine had to travel to Pope Clement VI in Avignon for confirmation. but on his return, he succumbed to the Black Death on 26 August. He had been archbishop for 40 days.

That career would not have secured his place in history, however, even with his work attacking the Pelagian heresy. As one of the Oxford Calculators, he developed the "mean speed" theorem and the Law of Falling Bodies before Galileo. He studied "star polygons" (how regular polygons "tile" or fit together in patterns) before Kepler. He developed mnemonic techniques to improve mental abilities, explaining them in De Memoria Artificiali (On Artificial Memory).

One of his theories involved the vacuum of space. Aristotle felt that a vacuum needed a container, because an open space would automatically become filled by matter outside that space flowing into it. Therefore, according to Aristotle, no vacuum could exist above the world, because there was no container beyond the world to maintain the vacuum. Bradwardine was not satisfied with this. The infinity of space was a hot topic in the Middle Ages and Renaissance. His De causa Dei (On the Causes of God) argued that God Himself was infinite, and therefore space beyond our world extended infinitely. (This was different from suggesting that God created separately a space that was infinite.) He also suggested that this infinity could include other worlds that God could create and rule over.

Robert Grosseteste

Robert Grosseteste (c.1170-1253) has been mentioned in several posts. His early life, beyond having been born into humble beginnings in Stowe, is unknown. One of our first notes about him is by Gerald of Wales (mentioned here), who recommended him in 1192 for a position in the household of the bishop of Hereford, William de Vere, because of Grosseteste's ability in liberal arts, canon law, and some medicine. He remained in de Vere's household until de Vere's death in 1198, after which Grosseteste drops out of the historical record almost completely.

We are sure he is the Robert Grosseteste who was appointed to the diocese of Lincoln in 1225 and concurrently as archdeacon of Leicester in 1229. The double-duties apparently made him ill within a few years, and he pared down to the position of canon in Lincoln Cathedral, and started lecturing in theology at Oxford on the side. According to Thomas of Eccleston, Franciscan chronicler for the years 1224-1258, Grosseteste joined the Franciscan school at Oxford around 1230.

Association with Oxford and reduced ecclesiastical responsibilities allowed him time for scientific theorizing and writing.

He began producing texts on the liberal arts, and mainly on astronomy and cosmology. His most famous scientific text, De luce (Concerning Light), argued that light was the basis of all matter, and his account of creation devotes a great deal of space to [...] God’s command, ‘Let there be light.’ Light also played a significant role [in] his epistemology, as he followed the teachings of St. Augustine that the human intellect comes to know truth through illumination by divine light. Grosseteste’s interest in the natural world was further developed by his study of geometry, and he is one of the first western thinkers to argue that natural phenomenon can be described mathematically. [source]

From De Sphera, on astronomy

For all his scientific interest, however, his first intellectual love was theology and the direction of the church. He clashed with the papacy several times, leading later scholars to try to label him an early Protestant. But correction is not insurrection (even though his influence can be seen in the writings of a true proto-Protestant, John Wycliffe). Now he is considered a valuable insight into the theology of his time, not a rebel.

There are 120 works attributed with confidence to him. They have not all been translated and examined yet. Focus has been on his theological and philosophical works, but many writings still exist only in manuscript form. His still-unedited scientific works may reinforce the current belief that he proves that pre-Renaissance scientific progress was further advanced than previously thought.

He died on 8 October, 1253, and was buried in a memorial chapel in Lincoln Cathedral.

Postscript: If you are curious about his Latin texts, seek
here.

The Father of Modern Optics

For a long time, there were two competing theories about how the eyes see—both wrong.

Alhazen ibn al-Haytham

Aristotle believed in what is called the intromission theory: the idea that actual physical forms enter the eye to plant images in your head. Euclid and Ptolemy believed in the theory of extromission: the idea that rays from the eyes went out and "scanned" or "detected" objects. Scholars and philosophers for centuries came down on one side or the other. It wasn't until the 11th century that a better theory came along.

Alhazen ibn al-Haytham (965-c.1040) was a Muslim who wrote about many topics. Originally he was a theologian, trying to address and reconcile the issues between the Shi'ah and Sunnah sects. He made his most lasting contributions, however, in the fields of astronomy, mathematics and optics. His Kitab al-Manazir (Book of Optics) changed the study of optics forever. He rejected both previous theories, arguing that there was no time for the eye to emit rays that could travel to a distant star and back to the eye instantly the way they would have to when first opening the eyes. He also refused to believe there was any mechanism that allowed forms to enter the eye. Instead, he opted (ha ha) for light coming from external objects to enter the eye, carrying an image of the object being looked at.

His theory of light's involvement in sight came when he realized that bright and dim light both affected visual perception, and that bright light left after-images on the eye. Also, it was obvious that perceiving color depended upon having sufficient light. He even invented the camera obscura in order to learn more about how light worked.

...and he did it while in prison.

Alhazen's diagram of the eye, with terms we still use

Earlier in his career, he became overconfident in his knowledge and made the mistake of claiming it would be possible to devise a way to control the annual spring flooding of the Nile. (Although born in Basra, Iraq, he lived his adult life in Cairo.) Hearing this, Caliph al-Hakim bi-Amr Allah, the sixth ruler of the Fatimid dynasty, ordered him to do so. When al-Haytham realized he wasn't able to perform this enormous feat of engineering, he tried to simply retire from the profession. The angry Caliph sent his men for al-Haytham, who feigned madness in order to avoid a death sentence for disappointing his all-powerful ruler. He was placed under house arrest, and devoted the remainder of his life to the sciences for which he is now known. Because of the experiments he conducted in order to test his theories, mirroring what would be known as the scientific method, some think of him as the "first scientist."

Hermann of Reichenau

Hermann, with crutch & Salve Regina

Hermann of Reichenau (1013-1054) was born to Count Wolverad II and his wife Hiltrud in Upper Swabia. He was severely disabled at birth, and had to be carried around in a specially built chair. A 1999 article tried to diagnose him based on contemporary reports.

Using the biography written by his disciple Berthold, [an] unbiased analysis of the symptoms described [...] is worked out: [...] Intellectual functions were unaffected. [...] Muscle disease is considered possible, but motor neuron disease - either amyotrophic lateral sclerosis or spinal muscular atrophy - seems to be the most convincing diagnosis. [C Brunhölzl, Thoughts on the illness of Hermann von Reichenau]

Because of his condition, he was nicknamed "Contractus" or "the Lame." When he was seven years old, his parents handed him over to the cloister school of the nearby Benedictine monastery on Lake Constance, where he studied under Abbot Berno. Berno was a well-known figure at the time for, among other things, his reforms in liturgical music. Hermann became a monk in 1043 and, upon Abbot Berno's death in 1048, became Berno's successor as abbot.

Despite Hermann's extreme difficulty in moving and even speaking, he was considered a devoted monk and brilliant scholar. He wrote a great deal on music, mathematics, and astronomy. As well as a treatise on the science of music, he wrote two of the best-known of the medieval liturgical songs, the Alma Redemptoris Mater (Loving Mother of the Redeemer), and the Salve Regina (Hail Holy Queen).*

Among his other accomplishments, he is credited with speaking Arabic, because through his writings he made available to the Latin West many scientific discoveries that were previously only widely known in the Arab world. This knowledge of Arabic, however, is only an assumption. His biographer, Berthold, never mentions knowledge of Arabic, which would be unusual omission for such an accomplishment. The monastery was a center of learning in the area, and very likely held copies of works by Gerbert of Aurillac, who learned much from Arabic sources in Spain.

Hermann wrote two works on the astrolabe, previously unknown in Europe, and described a portable sundial. His works on mathematics used Roman numerals. Although this precluded the use of decimals, he still achieved some remarkable results. In his Epistola de quantitate mensis lunaris (Letter on measurement of lunar months), he tries to find the average length of a lunar month. In decimal notation, it is 29.530851 days. Hermann did not only not have decimal notation, he didn't have minutes and seconds. In his time, the hour was divided into "moments" and "atoms." He calculates the length of the lunar month to be 29 days, 12 hours, 29 moments, 348 atoms, which turns out to be exactly right.

He also wrote a history called Chronicon ad annum 1054 (Chronicle to the year 1054). The original is lost, but a 1529 edition saved the unique historical knowledge inside. After Hermann's death, it was continued by Berthold; Berthold died in 1088, but the duty was taken up by others up until 1175.

Hermann died on 24 September. In 1863, he was beatified (a step toward being recognized as a saint). As Blessed Hermann of Reichenau, he is considered the patron of unborn babies, and his Feast Day is celebrated on 25 September.

*A popular English version of Salve Regina was prominent in the Whoopi Goldberg film "Sister Act."

Locks Through the Ages

Locks are mentioned as far back as the Old Testament. The book of Nehemiah, which describes events in the second half of the 5th century, makes mention in chapter 3 of repairing the gates of the City of Jerusalem, saying that they "set up the doors thereof, and the locks thereof, and the bars thereof." Whatever they meant by locks, they were clearly a part of the security different from bars and doors.

Late Medieval lock from Newcastle-upon-Tyne

We know that the Romans had barbed spring padlocks made of iron. A barbed hasp of metal under tension would catch on a hook inside the padlock, and a key would push in at the hook, releasing the barb so that the hasp would spring open.

A pin-tumbler lock—that uses internal pins (sometimes) of varying lengths that require a matching key pattern before they are in the proper alignment to allow the lock to open—was first patented in 1784 patent by Joseph Bramah. The modern version with which we are familiar today was patented in 1848 by Linus Yale Sr., and then modified by Linus Yale Jr. in 1861.

Mechanism of Egyptian pin-tumbler lock from Nineveh

Chances are that none of these gentlemen was aware that a 2700-year-old pin tumbler lock has been found in the Khorsabad palace in Nineveh.* It is made of wood. The key had four pins; it would be inserted into a channel in the bolt and lifted up to raise four tumblers up and out of the way so that the lock could be opened.

Between Khorsabad and Yale, the pin-tumbler lock was used all over Europe and Asia, changing very little in mechanics, but a lot in art design. As metal-smithing became more refined, the locks and keys became more complex. Locks and keys also became works of art, designed to fit visually with their intended purpose.

In medieval Europe, with men going off to war, important keys—to doors, chests that held valuables, coffers that held the lord's seal (needed for official documents) would be left with the trusted lady of the castle, the chatelaine (from Latin castellan, the "lady of the castle"). The symbol of the chatelaine became a cord or belt from which hung several keys. This led to the term "chatelaine" (still in use) to mean a chain or dangling clip used to organize items, such as a small pair of sewing scissors on a long chain.

*If you care to do your own searches on this topic, you'll frequently find the oldest lock is said to be 4000 years old or from 4000 BC. Since the references agree it was found in Khorsabad palace, which was built by Sargon II, who ruled 721-705 BCE, I have to assume online sources have been careless in their reporting of its age. Smith College is a little more careful with its description.