Today November 23 is Fibonacci Day.
This year it feels special after reading William Dalrymple's book "The Golden Road: How Ancient India Transformed the World"...
"...Five hundred years later, in 1205, Leonardo of Pisa, known by his nickname ‘Fibonacci’, returned from Algeria to Italy with his father. Fibonacci had grown up in a Pisan trading post in Bejaïa, where he had learned fluent Arabic as well as Arab mathematics. Aged thirty-two, he wrote the Liber Abaci, the ‘Book of Calculation’. It was he who first popularised in Europe the use of what were later thought of as ‘Arabic numerals’, so seeding the commercial revolution that financed the Renaissance and in time, as these ideas spread north, the economic rise of Europe.
But these numbers were not Arabic in origin. As Fibonacci and his Arab masters recognised, they were Indian. ‘When my father held the post of notary at the customs house at Bejaïa, he arranged for me to come to him when I was a boy,’ wrote Fibonacci in the introduction to his Liber Abaci.
Because he thought it useful for me, he wanted me to spend a few days there in the mathematical school, and to be taught there.
Here I was introduced to a wonderful kind of teaching that used the nine figures of the Indias. With the sign 0, which the Arabs call zephyr (al-sifr), any number whatsoever can be written. Getting to know this pleased me far beyond all else … Therefore concentrating on this method, I made an effort to compose this book, so that those seeking knowledge of this can be instructed by such a perfect method and so that in future the Latin race may not be found lacking this knowledge....
Fibonacci became probably the greatest mathematician of the European Middle Ages...
...The solution, generation by generation, was a series of numbers known as the celebrated Fibonacci Sequence. This was in turn related to the Golden Ratio, which Fibonacci realised was something which kept reappearing in nature: the spiralling of the chambers of the nautilus shell, for example, obeys this ratio. Although Fibonacci’s Liber Abaci contains the earliest known description of the sequence outside India, the sequence had been described by Aryabhata as early as the sixth century..."
