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Arabic Science II

Page history last edited by Garry Polley 12 years, 2 months ago




     Arabic science was far in advance of its Western counterparts until the scientific revolution. Contact with the Greek corpus, the development of trigonometry and the construction of observatories meant the Arabic astronomers could push the Ptolemaic model to its limits in accuracy. Influences from India (Hindu-Arabic numerals) and Babylonia allowed the development of algebra and arithmetic. Al-Khwarizimi for example, defined 'algebra' and 'algorithm', and used symbols such as 'x' for unknown quantities. He worked with equations, but they were written out in words. Al-Tusi developed trigonometry as a seperate field (Howard R. Turner, "Science in Medieval Islam"). Knowledge of Greek medicine, along with the religious imperative to help fellow man inspired the creation of hospitals with a quality of care and professionalism of staff found nowhere else in the world.




     Relying on the works from the Hellenistic Period, Arabic scholars turned toward resolving the debate between intromissionist and extromissionist theories of vision. Aristotle, in his intromissionist theory of optics, believed that light travels from the object to the eye and requires a medium in order to travel. The perception experienced is some distortion or alteration of the transparent medium caused by the object. The Atomists thought every object emits a simulacrum, or a small image of itself which peels off the object and enters into the eye. Euclid believed that a cone of vision radiated from the eye and intercepted objects which one then perceives - an extromissionist theory. Ptolemy developed a mathematical theory similar to Euclid's.


     Al-kindi, an Islamic natural philosopher who lived in the 9th century CE, argued that the intromissionist theory was not compatible with mathematics. If one looked at a circle edgewise, for example, there should be no way to tell whether it is a line or a circle. Alhazen, also known as Ibn al-Haytham, combined the intromissionist and extromissionist theories into a geometrical theory of light. He believed that the cone of vision was not physical. There would be no reason for observing the Sun to hurt the eyes, if the light originated in the eyes themselves. Alhazen hypothesized that rays are emitted from objects that give off light. He explained that only the rays that came perpendicular to the surface of the eye would enter it. He also made full use of experiments with all sorts of modifiers of natural light, including prisms. In his Book of Optics, he considered refraction, came close to a theory of magnifying lenses, and correctly explained the illusion of the changing diameter of the Sun and Moon. He made use of 'camera obscura' to study eclipses of the Sun projected onto a wall. Alhazen placed importance in the correlation of experiment and theory. His theory of light stood until Johannes Kepler replaced it in the 17th century CE.




     A similar debate as in optics occured in astronomy. Aristotle's cosmological model of rotating concentric spheres and his demand of circular motion in the heavens were irreconcilable with Ptolemy's models in general and his equant point specifically.


     One of the prominent theoretical astronomers that proposed a solution to this ongoing debate was Nasir al-Din al-Tusi, known as al-Tusi.  He implemented what is called the Tusi Couple - circles within circles, each with a uniform motion around its center, to account for the motion of the planets.  This model also proved that linear motion could result from different combinations of uniform circular motion, thus eroding the distinction between the celestial and terrestial realms. Ibn al-Shatir, a muwaqqit at the Damascus mosque, used Tusi's device to produce the most accurate model of planetary motion until the introduction of heliocentric theories. He was the first to succeed in modelling the motions of Mercury through uniform circular motion - a model later used by Copernicus.     

     Here is a model of Nasir's plantery motion.




     The most prominent Arabic observational astronomer was Al-Battani.  He wrote Kileb al-Zij, or On the Motion of the Stars. He found the solar year to be 365 days, 5 hours, 48 minutes, and 24 seconds and improved on the value of the inclination of the ecliptic. He also discovered that the values of the solar apogee and perigee change. Thabit ibn Qurra in turn, developed the theory of trepidation to explain the nonuniform precession of the equinoxes.


     Islamic astronomers also perfected the astrolabe from the original Greek design. The astrolabe, calibrated for different locations through replaceable plates, has many uses. It can tell where the celestial bodies lie in the Zodiac in a given day, give reference stars, determine latitude and longitude, and chart the rise and set of both the Sun and Moon. The Arab world was also concert to the invention of the quadrant, which is used to measure angles between stars in order to plot them effectively.




     The medical sciences also saw growth. Arabic physicians translated the works of earlier Greeks such as Galen, absorbed and modified their ideas. There were many great physicians in the Islamic tradition and many of them were prolific writers. Al-Rhazi (known as Rhazes) wrote such works as On the Fact that Even Skillful Physicians Cannot Heal All Diseases, Why People Prefer Quacks and Charlatans to Skilled Physicians, On Smallpox and Measles - which saw 40 editions between the 15th and 19th centuries in the West. He also wrote a comprehensive work Al-Hawi, in which he gathers previous thoughts on medicine and counters them with his own practical and rational opinions. Avicenna's Cannon became the reference text for medicine in the West. Ethics was also a concern. In the work of al-Ruhawi - The Physicians Code of Ethics, we find that a physician was to avoid money-grubbing and addiction, treat the poor and rich alike, answer questions patiently, give consent to demand for a second opinion, and explain all opinions to the patient.


     Ibn al-Nafis disovered pulmonary circulation. Ibn al-Khatib was the first to discuss epidemics in terms of contagion (H.R. Turner, "Science in Medieval Islam"). The greatest achievement, however, came in the form of hospitals. These included special wards for internal diseases, opthalmic disorders, orthopedic cases, surgical patients, mentally ill, and contagious diseases. Travelling clinics were organized to reach patients away from cities, and military hospitals travelled with armies. Physicians passed rigorous exams, experimented with treatments, and made detailed case write-ups available. Avicenna's Canon contains rules for experimental drug use, while al-Rhazi was notable for relying on experiment and criticizing even Galen.


Key Terms


apogee - here, the farthest distance from the Earth an object achieves during its orbit

astrolabe- ancient astronomical "computer" used to determine postition of celestial objects at a given time

perigee - here, the nearest an object comes to the Earth during its orbit

Tusi couple - circles within circles, each travelling with a uniform speed around its own center

intromissionist theory - a theory of vision, where the light travels from the object to the eye

extromissionist theory - a theory of vision, in which the eye emits a cone of radiation that reaches the object

simulacrum - a thin skin of atoms that peeled off an object and traveled into the eye

Comments (11)

jgm829@... said

at 8:41 am on Oct 2, 2008

I added some information on Islamic medicine.

Grant Berry said

at 8:57 am on Oct 2, 2008

I added info on intromissionist and extromissionist theories. There's plenty to still add, though.

liz mastroianni said

at 11:02 am on Oct 2, 2008

didnt have enough notes on anything else to add anything so just edited

Alyson Collins said

at 12:04 pm on Oct 2, 2008

Added some stuff on Arabic astronomy andcopied/put some terms down in the terms section. Don't know if I have the spelling of a few words/terms right if someone wants to check them.

jonathan stutte said

at 1:08 pm on Oct 2, 2008

didn't do much but add a little to Al-haytham

Kristy Carey said

at 1:18 pm on Oct 2, 2008

Edited and added bits and links on the astrolabe.

Larry_Crump said

at 3:22 pm on Oct 2, 2008

Um, not that I am particularly mad, but I think that this was my page to write, and given I just got on (voter registration has taken up my life), but it is pretty much written. I did, however take really in depth notes and will add anything not covered already.

Larry_Crump said

at 4:23 pm on Oct 2, 2008

I added relevant info about death and birth dates, analogies (pole and starry sky), more achievements of Al-Batani, and a section on Ibn al-Shattir. I also threw in all the inventions that the Arab world is responsible for.

Garrett McCormack said

at 3:23 pm on Oct 5, 2008

Just added a little about Arabic improvements in Greek science.

Nicole Hagstrom said

at 3:45 am on Oct 6, 2008

I divided up the page a fair bit and did more summary work. Also, did we go over Arabic medicine that day? I don't recall so, but I certainly could have just missed it.

Marek said

at 5:35 pm on Oct 17, 2008

Removed repetitions, added a bit on medicine and a key terms section

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