Leonardo Fibonacci

Little is known of Fibonacci’s personal life. It is not known whether he was married or not.

He was known by several names including Leonardo of Pisa, Leonardo Pisano Bigollo, and Leonardo Fibonacci.

The details regarding his death are also obscure. It is generally believed he died around 1240–50.

The exact date of Fibonacci’s birth is not known. It is believed he was born sometime around 1170–75 in Pisa. His father Guglielmo Bonacci was a wealthy Italian merchant who directed a trading post in North Africa. According to some sources, his father also served as the consul for Pisa.

As a young boy, Fibonacci travelled extensively with his father. He was primarily educated in Bejaia, a Mediterranean port in northeastern Algeria where his father was posted. He studied mathematics with an Arab master.

Continuing his travels, he visited Egypt, Syria, Greece, Sicily, and Provence. His travels gave him the opportunity to interact with merchants belonging to diverse cultures and he discussed the different methods of calculation with them. He was very much intrigued by the unique numerical systems adopted in different regions of the world.

Fibonacci was particularly fascinated by the ten symbols of the Hindu-Arabic numeral system—1, 2, 3, 4, 5, 6, 7, 8, 9 and most importantly, a symbol for zero 0. At that time Roman numerals were used in Europe for performing arithmetic calculations. This method was not an easy one and had several limitations.

The young mathematician was eager to introduce the Hindu-Arabic numerical system in Europe. Upon his return to Pisa around the year 1200, he wrote a number of texts on mathematics which played an important role in reviving ancient mathematical skills. He also produced several works drawing upon his own experiences and knowledge.

In 1202, he completed ‘Liber Abaci’ which was among the first Western books to describe Hindu-Arabic numbers traditionally described as "Arabic Numerals". At that time, Hindu-Arabic numerals were known to only a few European intellectuals through translations of the writings of the 9th century Arab mathematician al-Khwārizmī. Fibonacci helped to popularize the concept in the European world. His work gained fame quickly, and soon many copies of the work were made.

The Holy Roman emperor Frederick II who had a keen interest in science and mathematics came to know of Fibonacci through scholars at his court who had corresponded with Fibonacci. These scholars included Michael Scotus, Theodorus Physicus, and Dominicus Hispanus.

The emperor interacted with Fibonacci and the mathematician corresponded with Frederick and his scholars for several years. He collaborated with the scholars to work on mathematical problems, and presented the solutions to problems posed by Johannes of Palermo, in his work ‘Flos’ (1225). He dedicated his ‘Liber quadratorum’ (Book of Square Numbers) to Frederick.

Fibonacci is best known for his ‘Liber Abaci’, in which he popularized the system of the Hindu–Arabic numerals to the Western world. He advocated the use of the ten symbols—1, 2, 3, 4, 5, 6, 7, 8, 9, and 0—and showed how the system could be implemented for practical purposes like commercial bookkeeping and calculation of interest. The book profoundly impacted European thought.

In this work ‘Practica Geometriae’, he examined the techniques used in surveying and the measurement and partition of areas and volumes among other topics in practical geometry.

His book on algebra, ‘Liber quadratorum’ (Book of Square Numbers) examined several topics in number theory and gave an inductive method for finding Pythagorean triples. This work had a major influence on later mathematicians like Fermat and Euler.