Roger Bacon's "Opus Majus"

Roger Bacon was born about 1219 into a wealthy family in England. He attended classes at Oxford University, where he learned a love of science from masters such as Robert Grosseteste and Adam Marsh. About 1240 he joined the Franciscans, which might have stifled his interests. There was a prohibition on the order against publishing without special permission from the superiors. This was in place because of a work published previously that was considered heretical.

Bacon looked for support and patronage from the papal legate to England, telling him that educational reform was needed. This was one Gui Foucois, although in England he was known as Cardinal Guy de Foulques. The cardinal was not interested in providing financial aid, but was interested in his work and ideas. Unfortunately, without money, Bacon could not afford the writing materials and scientific equipment to produce what he wanted to send.

Then, in 1265, the situation changed. Guy de Foulques was elected Pope Clement IV. Another request to the new pope returned the same result: Clement wanted the information, but would not send money. Bacon could only assemble a shorter work than he wanted to. The result was the Opus Majus or Opus Maius (Latin: "Greater Work"). Its seven sections (which included some of his earlier writings along with new materials) are:

•The Four General Causes of Human Ignorance (believing in an unreliable source,  sticking to custom, ignorance shared by others, pretending to knowledge)
•The Affinity of Philosophy with Theology (concludes that Holy Scripture is the foundation of all sciences)
•On the Usefulness of Grammar (a study of Latin, Greek, Hebrew, Arabic)
•The Usefulness of Mathematics in Physics (in this section he proposes changes to fix the Julian calendar)
•On the Science of Perspective (the anatomy of the eye and brain; light, vision, reflection and refraction, etc.)
•On Experimental Knowledge (a review of alchemy, gunpowder, and hypothesizes microscopes, telescopes, eyeglasses, machines that fly, and ships driven be steam)
•A Philosophy of Morality (philosophy and ethics)

It was sent to Clement in late 1267 or early 1268; however, Clement died in 1268. We do not know if he even had opportunity to read what he had requested.

"The Science of Perspective" was about optics. In that section, he discussed the anatomy of the eye, and how light is affected by distance, reflection and refraction. He also goes into mirrors and lenses. Most of this knowledge of optics came from Alhazen's Book of Optics, previously discussed here, and Robert Grosseteste's work on optics based on Al-Kindi, of whom I have never written before; I think there's my next topic.

For more on Bacon, use the search feature in the blog.

Eyeglasses

Back here we spoke about the manufacture of glass, but when and where did glass come to be used for enhancing and correcting vision?

Ptolemy (c.100-170CE) wrote in his Optics about glass shaped so that it enlarged an image. His ideas were expanded on by the "Father of Modern Optics," Hasan Ibn al-Haytham, whose Book of Optics (c.1021) spread through Europe at (coincidentally?) about the same time that we get records of "reading stones."

A reading stone is a glob of transparent substance, flattened on the bottom but with a curved top, making it in essence a convex lens. It was (still IS, actually) meant to be placed on and slid along a line of text, causing the letters below to expand and be more easily read. I call it a "substance" because it wasn't necessarily glass. Early ones were ground from quartz, and they can be had today in glass or plastic.

Several lens-shaped items of quartz have been found in Viking graves on Gotland in Sweden, some mounted in silver. They date to the 11th or 12th centuries. They might be reading stones, although several are not shaped to be good at focusing.

But when were lenses put into a frame for enhancing vision? In 1301, in Venice, there were guild regulations governing the sale of eyeglasses. The Dominican friar Giordano da Pisa delivered a sermon in February 1306 in which he said:

It is not yet twenty years since there was found the art of making eyeglasses, which make for good vision... And it is so short a time that this new art, never before extant, was discovered. ... I saw the one who first discovered and practiced it, and I talked to him.

 So far as we can trace, then, eyeglasses were first made in Italy around 1290.

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 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."