Feb 172016


Today is the birthday (1201) of Khawaja Muhammad ibn Muhammad ibn Hasan Tūsī (Persian: محمد بن محمد بن الحسن طوسی‎‎), better known as Nasīr al-Dīn Tūsī (Persian: نصیر الدین طوسی‎)‎; or simply Tusi in the West, a Persian polymath and prolific writer – an architect, astronomer, biologist, chemist, mathematician, philosopher, physician, physicist, scientist, and theologian. The Muslim scholar Ibn Khaldoun (1332–1406) http://www.bookofdaystales.com/ibn-khaldoun/ considered Tusi to be the greatest of the later Persian scholars.

Tusi was born in the city of Tus in medieval Khorasan (in north-eastern Iran) and began his studies at an early age. In Hamadan and Tus he studied the Qur’an, Hadith, Shi’a jurisprudence, logic, philosophy, mathematics, medicine and astronomy.

He was apparently born into a Shī‘ah family and lost his father at a young age. Fulfilling the wish of his father, the young Tusi took learning and scholarship very seriously and travelled far and wide to attend the lectures of renowned scholars and acquire the knowledge, an exercise highly encouraged in his Islamic faith. At a young age he moved to Nishapur to study philosophy under Farid al-Din Damad and mathematics under Muhammad Hasib. He met also Farid al-Din ‘Attar, the legendary Sufi master who was later killed by Mongol invaders and attended the lectures of Qutb al-Din al-Misri.


In Mosul he studied mathematics and astronomy with Kamal al-Din Yunus (d. 1242). Later on he corresponded with Sadr al-Din al-Qunawi, the son-in-law of Ibn al-‘Arabi, and it seems that mysticism, as propagated by Sufi masters of his time, was not appealing to his mind and once the occasion was suitable, he composed his own manual of philosophical Sufism in the form of a small booklet entitled Awsaf al-Ashraf “The Attributes of the Illustrious”.

As the armies of Genghis Khan swept his homeland, he was employed by the Ismailis and made his most important contributions in science during this time when he was moving from one stronghold to another. He was captured after the invasion of the Alamut castle by the Mongol forces.


Tusi wrote about 150 works, of which 25 are in Persian and the remaining are in Arabic,[12] and there is one treatise in Persian, Arabic and Turkish. These include:

Kitāb al-Shakl al-qattāʴ Book on the complete quadrilateral. A five volume summary of trigonometry.

Al-Tadhkirah fi’ilm al-hay’ah – A memoir on the science of astronomy. Many commentaries were written about this work called Sharh al-Tadhkirah (A Commentary on al-Tadhkirah) – Commentaries were written by Abd al-Ali ibn Muhammad ibn al-Husayn al-Birjandi and by Nazzam Nishapuri.

Akhlaq-i Nasiri – A work on ethics.

al-Risalah al-Asturlabiyah – A Treatise on the astrolabe.

Zij-i ilkhani (Ilkhanic Tables) – A major astronomical treatise, completed in 1272.

sharh al-isharat (Commentary on Avicenna’s Isharat)

Awsaf al-Ashraf a short mystical-ethical work in Persian

Tajrīd al-iʿtiqād (Summation of Belief) – A commentary on Shia doctrines.

Talkhis Al Mohassal(summary of summaries).

During his stay in Nishapur, Tusi established a reputation as an exceptional scholar. “Tusi’s prose writing, which number over 150 works, represent one of the largest collections by a single Islamic author.

Tusi convinced Hulegu Khan to construct an observatory for establishing accurate astronomical tables for better astrological predictions. Beginning in 1259, the Rasad Khaneh observatory was constructed in Azarbaijan, south of the river Aras, and to the west of Maragheh, the capital of the Ilkhanate Empire.

Based on the observations in this for the time being most advanced observatory, Tusi made very accurate tables of planetary movements as depicted in his book Zij-i ilkhani (Ilkhanic Tables). This book contains astronomical tables for calculating the positions of the planets and the names of the stars. His model for the planetary system is believed to be the most advanced of his time, and was used extensively until the development of the heliocentric model in the time of Nicolaus Copernicus. Between Ptolemy and Copernicus, he is considered to be one of the most eminent astronomers of his time.


For his planetary models, he invented a geometrical technique called a Tusi-couple, which generates linear motion from the sum of two circular motions. He used this technique to replace Ptolemy’s problematic equant for many planets, but was unable to find a solution to Mercury’s motion, which was solved later by Ibn al-Shatir as well as Ali Qushji. The Tusi couple was later employed in Ibn al-Shatir’s geocentric model and Nicolaus Copernicus’ heliocentric model. He also calculated the value for the annual precession of the equinoxes and contributed to the construction and usage of some astronomical instruments including the astrolabe.

Ṭūsī criticized Ptolemy’s use of observational evidence to show that the Earth was at rest, noting that such proofs were not decisive. Although it doesn’t mean that he was a supporter of the motion of the earth, as he and his 16th-century commentator al-Bīrjandī, maintained that the earth’s immobility could be demonstrated, but only by physical principles found in natural philosophy. Tusi’s criticisms of Ptolemy were similar to the arguments later used by Copernicus in 1543 to defend the Earth’s rotation.

About the essence of the Milky Way, Ṭūsī in his Tadhkira writes: “The Milky Way, is made up of a very large number of small, tightly-clustered stars, which, on account of their concentration and smallness, seem to be cloudy patches. Because of this, it was likened to milk in color.” Three centuries later the proof of the Milky Way consisting of many stars came in 1610 when Galileo used a telescope to study the Milky Way and discovered that it is really composed of a huge number of faint stars.


In his Akhlaq-i-Nasri, Tusi put forward a basic theory for the evolution of species that has a few components that pre-echo Darwin. He begins his theory of evolution with the universe once consisting of equal and similar elements. According to Tusi, internal contradictions began appearing, and as a result, some substances began developing faster and differently from other substances. He then explains how the elements evolved into minerals, then plants, then animals, and then humans. Tusi then goes on to explain how hereditary variability was an important factor for biological evolution of living things:

The organisms that can gain the new features faster are more variable. As a result, they gain advantages over other creatures. . . . The bodies are changing as a result of the internal and external interactions.

Tusi then discusses how organisms are able to adapt to their environments:

Look at the world of animals and birds. They have all that is necessary for defense, protection and daily life, including strengths, courage and appropriate tools [organs]. Some of these organs are real weapons. For example, horns-spear, teeth and claws-knife and needle, feet and hoofs-cudgel. The thorns and needles of some animals are similar to arrows. Animals that have no other means of defense (as the gazelle and fox) protect themselves with the help of flight and cunning. Some of them, for example, bees, ants and some bird species, have united in communities in order to protect themselves and help each other.

Tusi next explains how humans evolved from animals:

Such humans [probably anthropoid apes] live in the Western Sudan and other distant corners of the world. They are close to animals by their habits, deeds and behavior. The human has features that distinguish him from other creatures, but he has other features that unite him with the animal world, vegetable kingdom or even with the inanimate bodies. Before [the creation of humans], all differences between organisms were of the natural origin. The next step will be associated with spiritual perfection, will, observation and knowledge. All these facts prove that the human being is placed on the middle step of the evolutionary stairway. According to his inherent nature, the human is related to the lower beings, and only with the help of his will can he reach the higher development level.

In chemistry and physics, Tusi stated a version of the law of conservation of mass. He wrote that a body of matter is able to change, but is not able to disappear:

A body of matter cannot disappear completely. It only changes its form, condition, composition, color and other properties and turns into a different complex or elementary matter.

Tusi was the first to write a work on trigonometry independently of astronomy. In his Treatise on the Quadrilateral, gave an extensive exposition of spherical trigonometry, distinct from astronomy. It was in these works that trigonometry achieved the status of an independent branch of pure mathematics distinct from astronomy, to which it had previously been linked.

In his On the Sector Figure, appears the famous law of sines for plane triangles.

a/sin A = b/sin B = c/sin C

He also stated the law of sines for spherical triangles, discovered the law of tangents for spherical triangles, and provided proofs for these laws.


In February 2013, Google celebrated his 812th birthday with a doodle, which was accessible in its websites with Arabic language calling him al-farsi (the Persian). Arils are the seeds, which act as a garnish.

Pomegranate soup, or āsh-e anār, is a Persian and Mesopotamian dish (āsh) made from pomegranate juice and seeds, yellow split peas, rice, spices, and vegetables. It likely has ancient roots. It is generally more flavorful if you can find pomegranate syrup, but the pure juice will do.


Pomegranate Soup


2 tbsp extra virgin olive oil
1 cup fresh parsley, chopped
¾ cup fresh cilantro, chopped (or mint)
1 cup fresh spinach, chopped
1 leek, washed and sliced thin
8 cups light stock
⅓ cup fresh lemon juice
½ cup basmati rice, uncooked
⅓ cup yellow split peas, soaked overnight
¼ cup pomegranate syrup
2 tbsp sugar
freshly ground black pepper
pomegranate arils to garnish


Heat the olive oil in a large, heavy stock pot on medium heat. Add the parsley, cilantro, spinach and leek, and sauté for 10 minutes to wilt. Do not allow them to take on color.

Add the stock and lemon juice and bring to a simmer. Add the rice and split peas. Cook on a low heat until the rice is done (about 30 minutes). The split peas will cook at about the same time.

Add the pomegranate syrup and sugar. Season to taste with salt and pepper and simmer for another 10 minutes.

Pour the soup into deep bowls and garnish with about 1 tablespoon of pomegranate arils per bowl.

Serve with flatbread.

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