Optics (Ptolemy)

Last updated
A 16th-century engraving of Ptolemy. Ptolemy 16century.jpg
A 16th-century engraving of Ptolemy.

Ptolemy's Optics is a 2nd-century book on geometrical optics, dealing with reflection, refraction, and colour. The book was most likely written late in Ptolemy's life, after the Almagest , during the 160s. [1] The work is of great importance in the early history of optics. The Greek text has been lost completely. Fragments of the work survive only in the form of a Latin translation, prepared around 1154 by Eugene of Palermo, based on an Arabic translation which was presumably based on the Greek original. Both the Arabic and the Greek texts are lost entirely, and the Latin text is "badly mangled". [2] The Latin text was edited by Albert Lejeune in 1956. The 1996 English translation by Mark Smith is based on Lejeune's Latin text.

Contents

Textual history

The work is known to have been received by Arabic scholars working on optics in the 10th and 11th century, specifically Ibn Sahl (c. 984) and Ibn Al-Haytham (Alhazen), author of the influential Book of Optics (c. 1020). There are only three known references to the existence of the Greek text of the work, dated to the 4th, 6th and 11th centuries. The latest of these, produced by Simeon Seth, may however only be at second hand, so that it is uncertain whether the Greek text was still available in the medieval period, and the relation of the Arabic text available to Alhazen is unknown. On the other hand, the content of the Latin text produced by Eugene can to some extent be compared to the Arabic text available to Alhazen: both were structured in five books, and both are missing the first book entirely and the fifth book in part. [3] By contrast to the garbled state of the Arabic text and the complete loss of any Greek or Arabic manuscripts, the preservation of Eugene's Latin text is very good, the text being extant in 13 manuscripts, the oldest of which date to the early 14th century. [4]

Eugene's text was influential in the late medieval and Renaissance-era development of optics, even though its importance was overshadowed by the publication of the Latin translation of Alhazen's De aspectibus at the turn of the 13th century. Ptolemy's Optics is mentioned by Roger Bacon and Regiomontanus planned a printed edition (which was never published). The scientific progress made in the 16th and 17th centuries rendered the work so completely obsolete that it was considered a lost work by the mid-18th century. Manuscripts of the Latin text were recovered by philologists in the late 18th century, and in the 1820s there were once again preparations for the work's publication, which again came to nothing. A first edition finally appeared in 1885, prepared by Gilberto Govi. The first and still authoritative critical edition of the text is that of Lejeune, published in 1956.

Contents

Refraction of light at the interface between air and water. Ptolemy's Optics contains the earliest surviving table giving the relationship between the angle of incidence (th1) and the angle of refraction (th2) Snells law2.svg
Refraction of light at the interface between air and water. Ptolemy's Optics contains the earliest surviving table giving the relationship between the angle of incidence (θ1) and the angle of refraction (θ2)

The work contains the earliest surviving table of refraction from air to water, for which the values (with the exception of the 60° angle of incidence), although historically praised as experimentally derived, appear to have been obtained from an arithmetic progression. [5]

However, according to Mark Smith, Ptolemy's tables were based on real experiments. His "adjustment" of the data, using arithmetic progression, is essentially the method of regularizing irregularly-changing values, which was often used by astronomers. This was done in order to organize and make sense of the tables' data in a rational way. [6]

Ptolemy also presents a theory of vision. In his view, rays (or flux) are emitted from the eye. The rays are sensitive, and convey information back to the observer's intellect about the distance and orientation of surfaces. Size and shape were determined by the visual angle subtended at the eye combined with perceived distance and orientation. This was one of the early statements of size-distance invariance as a cause of perceptual size and shape constancy, a view supported by the Stoics. [7]

Ptolemy offered explanations for many phenomena concerning illumination and colour, size, shape, movement and binocular vision. He also divided illusions into those caused by physical or optical factors and those caused by judgmental factors. He offered an obscure explanation of the sun or moon illusion (the enlarged apparent size on the horizon) based on the difficulty of looking upwards. [8] [9]


See also

Related Research Articles

<span class="mw-page-title-main">Ibn al-Haytham</span> Arab physicist, mathematician and astronomer (c. 965 – c. 1040)

Ḥasan Ibn al-Haytham, Latinized as Alhazen, was a medieval mathematician, astronomer, and physicist of the Islamic Golden Age from present-day Iraq. Referred to as "the father of modern optics", he made significant contributions to the principles of optics and visual perception in particular. His most influential work is titled Kitāb al-Manāẓir, written during 1011–1021, which survived in a Latin edition.

<span class="mw-page-title-main">Ptolemy</span> 2nd-century Roman mathematician, astronomer, geographer

Claudius Ptolemy was a Roman mathematician, astronomer, astrologer, geographer, and music theorist, who wrote about a dozen scientific treatises, three of which were of importance to later Byzantine, Islamic, and Western European science. The first is the astronomical treatise now known as the Almagest, although it was originally entitled the Mathēmatikē Syntaxis or Mathematical Treatise, and later known as The Greatest Treatise. The second is the Geography, which is a thorough discussion on maps and the geographic knowledge of the Greco-Roman world. The third is the astrological treatise in which he attempted to adapt horoscopic astrology to the Aristotelian natural philosophy of his day. This is sometimes known as the Apotelesmatika but more commonly known as the Tetrábiblos, from the Koine Greek meaning "Four Books", or by its Latin equivalent Quadripartite.

<span class="mw-page-title-main">Roger Bacon</span> Medieval philosopher and theologian

Roger Bacon, also known by the scholastic accolade Doctor Mirabilis, was a medieval English philosopher and Franciscan friar who placed considerable emphasis on the study of nature through empiricism. In the early modern era, he was regarded as a wizard and particularly famed for the story of his mechanical or necromantic brazen head. He is sometimes credited as one of the earliest European advocates of the modern scientific method, along with his teacher Robert Grosseteste. Bacon applied the empirical method of Ibn al-Haytham (Alhazen) to observations in texts attributed to Aristotle. Bacon discovered the importance of empirical testing when the results he obtained were different from those that would have been predicted by Aristotle.

<i>Almagest</i> Astronomical treatise by Claudius Ptolemy

The Almagest is a 2nd-century Greek-language mathematical and astronomical treatise on the apparent motions of the stars and planetary paths, written by Claudius Ptolemy. One of the most influential scientific texts in history, it canonized a geocentric model of the Universe that was accepted for more than 1,200 years from its origin in Hellenistic Alexandria, in the medieval Byzantine and Islamic worlds, and in Western Europe through the Middle Ages and early Renaissance until Copernicus. It is also a key source of information about ancient Greek astronomy.

<span class="mw-page-title-main">Gerard of Cremona</span> Italian translator and astrologer

Gerard of Cremona was an Italian translator of scientific books from Arabic into Latin. He worked in Toledo, Kingdom of Castile and obtained the Arabic books in the libraries at Toledo. Some of the books had been originally written in Greek and, although well known in Byzantine Constantinople and Greece at the time, were unavailable in Greek or Latin in Western Europe. Gerard of Cremona is the most important translator among the Toledo School of Translators who invigorated Western medieval Europe in the twelfth century by transmitting the Arabs' and ancient Greeks' knowledge in astronomy, medicine and other sciences, by making the knowledge available in Latin. One of Gerard's most famous translations is of Ptolemy's Almagest from Arabic texts found in Toledo.

<span class="mw-page-title-main">Science in the medieval Islamic world</span> Science developed and practised during the Islamic Golden Age

Science in the medieval Islamic world was the science developed and practised during the Islamic Golden Age under the Umayyads of Córdoba, the Abbadids of Seville, the Samanids, the Ziyarids, the Buyids in Persia, the Abbasid Caliphate and beyond, spanning the period roughly between 786 and 1258. Islamic scientific achievements encompassed a wide range of subject areas, especially astronomy, mathematics, and medicine. Other subjects of scientific inquiry included alchemy and chemistry, botany and agronomy, geography and cartography, ophthalmology, pharmacology, physics, and zoology.

<span class="mw-page-title-main">Moon illusion</span> Optical illusion involving the Moon

The Moon illusion is an optical illusion which causes the Moon to appear larger near the horizon than it does higher up in the sky. It has been known since ancient times and recorded by various cultures. The explanation of this illusion is still debated.

<span class="mw-page-title-main">Emission theory (vision)</span>

Emission theory or extramission theory or extromissionism is the proposal that visual perception is accomplished by eye beams emitted by the eyes. This theory has been replaced by intromission theory, which is that visual perception comes from something representative of the object entering the eyes. Modern physics has confirmed that light is physically transmitted by photons from a light source, such as the sun, to visible objects, and finishing with the detector, such as a human eye or camera.

<span class="mw-page-title-main">Plato Tiburtinus</span>

Plato Tiburtinus was a 12th-century Italian mathematician, astronomer and translator who lived in Barcelona from 1116 to 1138. He is best known for translating Hebrew and Arabic documents into Latin, and was apparently the first to translate information on the astrolabe from Arabic.

<span class="mw-page-title-main">Catoptrics</span> Study of the relationship between light and mirrors

Catoptrics deals with the phenomena of reflected light and image-forming optical systems using mirrors. A catoptric system is also called a catopter (catoptre).

<span class="mw-page-title-main">Ibn Sahl (mathematician)</span> Mathematician (c. 940-1000)

Ibn Sahl was a Persian mathematician and physicist of the Islamic Golden Age, associated with the Buyid court of Baghdad. Nothing in his name allows us to glimpse his country of origin.

<span class="mw-page-title-main">History of optics</span>

Optics began with the development of lenses by the ancient Egyptians and Mesopotamians, followed by theories on light and vision developed by ancient Greek philosophers, and the development of geometrical optics in the Greco-Roman world. The word optics is derived from the Greek term τα ὀπτικά meaning 'appearance, look'. Optics was significantly reformed by the developments in the medieval Islamic world, such as the beginnings of physical and physiological optics, and then significantly advanced in early modern Europe, where diffractive optics began. These earlier studies on optics are now known as "classical optics". The term "modern optics" refers to areas of optical research that largely developed in the 20th century, such as wave optics and quantum optics.

<i>Geography</i> (Ptolemy) Treatise on cartography by Claudius Ptolemaeus

The Geography, also known by its Latin names as the Geographia and the Cosmographia, is a gazetteer, an atlas, and a treatise on cartography, compiling the geographical knowledge of the 2nd-century Roman Empire. Originally written by Claudius Ptolemy in Greek at Alexandria around AD 150, the work was a revision of a now-lost atlas by Marinus of Tyre using additional Roman and Persian gazetteers and new principles. Its translation into Arabic in the 9th century and Latin in 1406 was highly influential on the geographical knowledge and cartographic traditions of the medieval Caliphate and Renaissance Europe.

<span class="mw-page-title-main">Latin translations of the 12th century</span>

Latin translations of the 12th century were spurred by a major search by European scholars for new learning unavailable in western Europe at the time; their search led them to areas of southern Europe, particularly in central Spain and Sicily, which recently had come under Christian rule following their reconquest in the late 11th century. These areas had been under Muslim rule for a considerable time, and still had substantial Arabic-speaking populations to support their search. The combination of this accumulated knowledge and the substantial numbers of Arabic-speaking scholars there made these areas intellectually attractive, as well as culturally and politically accessible to Latin scholars. A typical story is that of Gerard of Cremona, who is said to have made his way to Toledo, well after its reconquest by Christians in 1085, because he

arrived at a knowledge of each part of [philosophy] according to the study of the Latins, nevertheless, because of his love for the Almagest, which he did not find at all amongst the Latins, he made his way to Toledo, where seeing an abundance of books in Arabic on every subject, and pitying the poverty he had experienced among the Latins concerning these subjects, out of his desire to translate he thoroughly learnt the Arabic language....

Abdelhamid Ibrahim Sabra (1924-2013) was a professor of the history of science specializing in the history of optics and science in medieval Islam. He died December 18, 2013. Sabra provided English translation and commentary for Books I-III of Ibn al-Haytham's seven book Kitab al-Manazir, written in Arabic in the 11th century.

Eugenius of Palermo was an amiratus (admiral) of the Kingdom of Sicily in the late twelfth century.

<i>Book of Optics</i> 11th century treatise on optics by Ibn al-Haytham

The Book of Optics is a seven-volume treatise on optics and other fields of study composed by the medieval Arab scholar Ibn al-Haytham, known in the West as Alhazen or Alhacen.

<span class="mw-page-title-main">Islamic world contributions to Medieval Europe</span> Influence of Islamic civilisation on Medieval Europe

During the High Middle Ages, the Islamic world was at its cultural peak, supplying information and ideas to Europe, via Al-Andalus, Sicily and the Crusader kingdoms in the Levant. These included Latin translations of the Greek Classics and of Arabic texts in astronomy, mathematics, science, and medicine. Translation of Arabic philosophical texts into Latin "led to the transformation of almost all philosophical disciplines in the medieval Latin world", with a particularly strong influence of Muslim philosophers being felt in natural philosophy, psychology and metaphysics. Other contributions included technological and scientific innovations via the Silk Road, including Chinese inventions such as paper and gunpowder.

The natural sciences saw various advancements during the Golden Age of Islam, adding a number of innovations to the Transmission of the Classics. During this period, Islamic theology was encouraging of thinkers to find knowledge. Thinkers from this period included Al-Farabi, Abu Bishr Matta, Ibn Sina, al-Hassan Ibn al-Haytham and Ibn Bajjah. These works and the important commentaries on them were the wellspring of science during the medieval period. They were translated into Arabic, the lingua franca of this period.

Euclids <i>Optics</i> Book by Euclides van Alexandrië

Euclid's Optics, is a work on the geometry of vision written by the Greek mathematician Euclid around 300 BC. The earliest surviving manuscript of Optics is in Greek and dates from the 10th century AD.

References

  1. Smith 1996, p. 3.
  2. Smith 1996, p. 5.
  3. Smith (1996), p. 3, referencing Lejeune (1956), p. 27.
  4. Lindberg 1975.
  5. Boyer 1959.
  6. Smith 2015, pp. 116–118.
  7. Ross & Plug 1998.
  8. Ross & Ross 1976, p. 377.
  9. Sabra 1987.

Bibliography