Fibonacci

Leonardo Bonacci, known as Fibonacci, was an Italian mathematician who lived around the year 1200. He came from the Republic of Pisa and is often called the best Western mathematician of the Middle Ages.

Fibonacci helped introduce the numbers we use today, called the Indo–Arabic numeral system, to Europe. He wrote a famous book in 1202 called Liber Abaci, which means "Book of Calculation." This book showed how to use these new numbers for everyday math problems.

In his book, Fibonacci used a special list of numbers now called the Fibonacci numbers. These numbers start with 0 and 1, and each new number is the sum of the two before it, like 0, 1, 1, 2, 3, 5, and so on. This idea has become important in many areas of math and nature.

Biography

Fibonacci was born around 1170 in a place called Bugia, which is now Béjaïa in Algeria. As a young boy, he traveled with his father, a merchant, and learned about numbers using the Hindu–Arabic numeral system. This system was much easier for calculations than the Roman numerals used in Europe at the time.

Fibonacci traveled around the Mediterranean and learned from many merchants. In 1202, he wrote a book called Liber Abaci, which helped introduce the Hindu-Arabic numerals to Europe. Later, he advised Emperor Frederick II on mathematics and was honored by the Republic of Pisa for his work.

Liber Abaci

Main article: Liber Abaci

In the Liber Abaci (1202), Fibonacci introduced a new way of writing numbers called the modus Indorum, or the method of the Indians. Today, we call this the Hindu–Arabic numeral system, which uses ten digits, including a zero, and positional notation. The book showed how useful these numbers were for everyday tasks like keeping track of money, changing weights and measures, and calculating interest. This made business much easier and helped grow banking and accounting in Europe.

Although the original 1202 manuscript is lost, a copy from 1228 shows how Fibonacci compared these new numbers to older ones like Roman numerals. The book also taught how to use these numbers for tasks such as changing currencies and figuring out profits, as well as discussing special kinds of numbers like irrational numbers and prime numbers.

Fibonacci sequence

Fibonacci solved a problem about how rabbit families grow, which led to a special list of numbers now called Fibonacci numbers. In this list, each number is the sum of the two numbers before it. Fibonacci started his list with 1, 2, 3, and went up to the thirteenth number, which is 233. Indian mathematicians had used this idea even earlier, way back in the sixth century. Fibonacci did not talk about the golden ratio, which is what we get when we divide one number in the list by the number before it.

Legacy

In the 19th century, a statue of Fibonacci was placed in Pisa, and today it can be found in the western gallery of the Camposanto, a historical cemetery on the Piazza dei Miracoli.

Many mathematical ideas are named after Fibonacci because of their link to the Fibonacci numbers. These include the Brahmagupta–Fibonacci identity, the Fibonacci search technique, and the Pisano period. Beyond math, Fibonacci’s name is also used for things like the asteroid 6765 Fibonacci and the art rock band The Fibonaccis.

Works

Fibonacci wrote several important books. One of his most famous works is Liber Abaci, written in 1202, which focused on calculations. Another book, Practica Geometriae from 1220, covered useful geometry skills for measuring land and objects. He also wrote Flos in 1225, which gave solutions to math problems. One of his other works, Liber quadratorum, discussed special math equations and was dedicated to Emperor Frederick II. Two of his other books, Di minor guisa and a Commentary on Book X of Euclid's Elements, are unfortunately lost today.