al-Kindi - الكندي

Yaqub ibn Ishaq al-Kindi

Abu Yusuf Yaqub ibn Ishaq al-Kindi (175 AH/873-800 CE) (185 AH – 256 AH / 805 – 873 CE) There is a five-year discrepancy in the calculation of his age. His full name is Yaqub ibn Ishaq ibn al-Sabbah al-Kindi, Abu Yusuf. He belonged to the Kinda tribe, whose homeland was in the southwestern region of Najd. He is known to the Latins as Alkindus. He was born in Kufa, and his father was its governor. It is said that Yaqub al-Kindi memorized the Quran and many of the Prophet’s hadiths by the age of fifteen while living in Kufa with his wealthy family after the death of his father, the governor of Kufa, who left him and his siblings a great deal of money. Yaqub wanted to learn more about the sciences of his time, so he decided to travel with his mother to Basra to study Kalam (Islamic theology), a science among the Arabs that was comparable to philosophy among the Greeks. Al-Kindi spent three years in Basra studying, during which he learned everything he needed to know about Kalam. He then completed his studies under the most famous scholars in Baghdad, where he and his mother moved to a house to further his education and knowledge, as Baghdad during the Abbasid era was a sea of ​​diverse sciences. He began frequenting the House of Wisdom library, which was established by Harun al-Rashid and flourished during the reign of his son al-Ma’mun. He would spend entire days there reading books translated from Greek, Persian, and Indian languages. However, his thirst for knowledge did not stop at reading translated books; he wished to be able to read books that had not been translated in their original languages. Therefore, he began studying Syriac and Greek under two teachers who came to his home to instruct him. Yaqub mastered these two languages ​​after two years and began to pursue his dream. He formed his own team and established a school of translation that relied on a beautiful style that did not alter the meaning of the translated text but made it easy to understand, free from awkwardness and weakness. He built a library in his home that rivaled the House of Wisdom in its size, and people began to frequent his house for learning and his library for reading. His fame spread throughout the land when he was only twenty-five years old. Caliph Al-Ma’mun invited him for a meeting, was impressed by him, and they quickly became friends. Later, Al-Kindi developed a new methodology for the sciences, reconciling religious and secular knowledge. He possessed extensive knowledge of Greek science and philosophy. He lived during the reigns of three Abbasid caliphs: Al-Ma’mun, Al-Mu’tasim, and Al-Mutawakkil. He also lived alongside the three Banu Musa brothers, who were astronomers, and the astronomer Sind ibn Ali. He attained a high position with Al-Ma’mun and Al-Mu’tasim, to the extent that Al-Ma’mun entrusted him with translating the works of Aristotle and other Greek philosophers. Al-Mutawakkil also employed him as a calligrapher, but due to his philosophical views and the slander of some envious individuals, Al-Mutawakkil ordered the confiscation of all his books. However, they were all returned to him. Al-Kindi recognized the importance of mathematics in worldly sciences, so he developed a methodology that established the use of mathematics in many sciences. Mathematics is a fundamental science that is incorporated into engineering, logic, arithmetic, and even music. Al-Kindi used mathematics and the Greek musical scale invented by Pythagoras to create the first scale for Arabic music, naming the musical notes. He was also the first to describe the principles of what is now known as the theory of relativity. While traditional mechanics scientists (Galileo and Newton) considered time, space, motion, and objects as absolute values, Al-Kindi said that these values ​​are relative to each other, as well as relative to their observer. Al-Kindi is also nicknamed the philosopher of the Arabs, and many consider him the founder of Arabic-Islamic philosophy. Cardano considered him one of the twelve geniuses who appeared in the world. He was a polymath; in addition to his fame as a philosopher, he was a scholar of mathematics, astronomy, physics, medicine, pharmacology, and geography. Like most scholars of his time, he was a polymath: a mathematician, physicist, astronomer, and philosopher, in addition to being a musician, as Al-Kindi is considered the creator of the first scale for Arabic music.
His scientific contributions:
He wrote four books on the use of Indian numerals. He also made significant contributions to spherical geometry to assist him in his astronomical studies. He observed the positions of the stars and planets—especially the sun and moon—in relation to the Earth and their natural effects and the phenomena that arise from them. He presented serious and bold ideas in these studies, and on the origin of life on Earth, which led many scientists to acknowledge Al-Kindi as a profound thinker of the highest caliber. In chemistry, he opposed the idea that precious metals such as gold could be extracted from base metals. He wrote a treatise on this subject, which he titled “Treatise on the Invalidity of the Claims of Those Who Claim to Make Gold and Silver and Their Deceptions.” In astronomy, al-Kindi did not believe in the influence of the planets on human affairs, and he rejected the predictions made by astrologers based on the movements of celestial bodies. He focused his attention on the scientific study of astronomy, celestial bodies, and their observations. Some historians consider him one of the eight leading figures in the science of astronomy in the Middle Ages for his contribution to the development of the astronomical observatory in Baghdad. Al-Kindi made significant contributions to physics, particularly in geometrical and physiological optics, and authored a book on the subject that later influenced Roger Bacon, Witelo, and others. Al-Kindi was also a skilled engineer, and his writings and theories were consulted in construction projects, especially in the construction of canals, as was the case when digging canals between the Tigris and Euphrates rivers.
In his book on light, al-Kindi indicated that light travels in straight lines, resulting in direct vision if the medium allows light to pass through it. Vision through glass is possible because it is transparent, meaning that glass allows light to pass through in straight lines, thus providing clear vision, unlike opaque objects that do not allow light to pass through. Al-Kindi studied the effect of long distances on vision and the deviation of angles in the theoretical effect on vision when light passes through two different transparent media, and the occurrence of optical illusions. This indicates that al-Kindi understood the reflection and refraction of light, explained the phenomenon, and defined the angles, albeit without precise measurements. He left all of this to his successor, Ibn al-Haytham, who was able to quantify these phenomena.