Our world is full of mysteries and interesting things once found out by someone. This is irrefutably true to our days. The globe is cyclic. There is a variety of sequences making our life better. Today, we will talk about one of such inventors. He found a sequence possibly facilitating the life system. Let’s check what and when National Fibonacci Day in 2021 is.

**Well, it is celebrated on 23rd of November.** The aim is to recall the importance of the invention discovered in 12th century by Leonardo Bonacci. Interestingly, the celebration date – 23 – is chosen to accord to his sequence.

## History

Leonardo was born in the Pisa Republic around 1170. His father, Guglielmo Bonacci, was a wealthy merchant and a representative of the Pisa Republic in the East. The boy lived for several years in Algiers. There, he studied arithmetic methods widely known among scholars of the Islamic world but mostly inaccessible in the West. Through communication with Western merchants, he mastered the mathematical techniques adopted in Europe. Later, he traveled extensively in the East, combining mathematical studies with commerce. His talent in mathematics was seen at the court of Frederick II. The emperor appointed the mathematician a lifelong content. It allowed him to concentrate on his studies.

In 1202, Leonardo published the main work “The Book of the Abacus”. He reissued it in 1228. It contains all the arithmetic and algebraic information of the time, set out to exceptional completeness and depth. It visibly rises above the European mathematical literature of the 12th and 14th centuries. It has much better variety and power of methods, the richness of tasks, and the veracity of solutions. Subsequent mathematicians widely draw from it both problems and methods for their solution. In the “Book of the Abacus”, he puts into circulation Arabic numerals and the zero sign for the first time in Europe. He even gives a table in which the Roman and Arabic numbers designation systems were matched. Until the publication, the Roman and Greek systems of calculus were used. The new system proposed by him was not immediately appreciated. Its adoption and dissemination were not without difficulties. **Thus, in 1280 in Florence, bankers were forbidden to use Arabic numerals.**

Simultaneously in Europe, Roman numerals were used. They are terribly inconvenient to operate both with complex mathematical and physical calculations. To say nothing about the routine work with finance and accounting. Leonardo presented Europe with Arabic numerals. They are used by the whole Western world to this day. The transition from the Roman system to the Arab one revolutionized mathematics and other sciences.

It is hard to imagine, what the world would have been like if, in the 13th century, the mathematician had not published his masterpiece and had not expounded the Arab figures to Europeans. Interestingly, we use Arabic numerals without thinking. We take them for granted. But if it were not for him, who knows how the course of history would have evolved. The representation and treatise of the Arabic numerals significantly changed medieval mathematics for the better. *Physics and mechanics also benefited from it. In many ways, the course of history, the development of European civilization and science is due to Leonardo of Pisa.*

### A series of Fibonacci numbers

Later it became clear – this sequence of numbers is important not only in mathematics, economics, technical analysis, and finance. It also appeared in botany, zoology, physiology, medicine. Even in art, philosophy, and aesthetics.

In the sequence, each element, starting with the third, is the sum of the two previous elements. The series start with the numbers 0 and 1. The order is: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233…

The ratio of the two neighboring elements of the series tends to the Golden Section, i.e. to 1,618… The uniqueness of this number is that it is one of the solutions of the equation x + 1 = x2. Think about the meaning of this simple square trinomial. If you do not see the beauty and mystery, then you are not the friend of mathematics.

**The Golden Section and The application value of the Fibonacci series deserve a separate article.** The elements of the sequence are used to calculate moving averages (not to mention the growth of the population of rabbits). Many masterpieces of world art contain the Golden Section.

The name of Leonardo of Pisa will be mentioned in our world more than once. Especially, in any publication on the topic of finance.

## Meaning

What does Fibonacci Day mean to Americans? It means that they get acquainted with this invention. They meet to discuss some misunderstood issues. People go out and make a theme picnic. Moreover, if they have children, they introduce them to the basics of mathematics. So, it’s easy to find out what day Fibonacci Day in 2021 is, by talking with Americans.

### Definition

The question When is Fibonacci Day in 2021 is linked directly with his invention. But what is the use of his theory in nature?

*Shells of snails are wrapped according to the Fibonacci sequence rule. Similarly, the shells of a nautilus obey the same rule.* The only difference is that the shells of a nautilus grow on a three-dimensional spiral. Meanwhile, the shells of snails are two-dimensional.

Moreover, in 1993, Robert Fisher published a book under the working title “Applications and Fibonacci Strategies for Traders” in Wiley & Sons. It described Leonardo’s basic discoveries and inventions in application to complex strategies of the profitable trading. The book is still popular.

## Traditions

Many years, this date is celebrated over the world with a huge success related to the invention essence. **How to celebrate it in 2021:**

- Recall the scientist’s biography and his theories in math.
- If you don’t know it yet, then introduce the whole information about his life and progress to your mind.
- Have you got children? Let them get acquainted with first steps in mathematics! Let it be Fibonacci sequence. The rule is easy to understand even by children.
- Visit thematic conferences, meetings, and debating societies held from 8 am to 22 pm yearly on
**23 of November**.

### National Fibonacci Day Facts

- Complex and surprising properties of the sequence have always been of interest to various mathematicians. Many of them came to the conclusion that the numbers of these series represent the encrypted code of nature.
*The golden number was found during the study of the ancient pyramids constructions.*The number 1.618 plays a central role in all external and internal proportions of the pyramids. Some scholars are inclined to think these pyramids were built by ancient Egyptians with only one purpose – to transfer their knowledge to subsequent generations.

Numeric series surround us constantly. Often, we don’t pay attention to this fact. If you want to enjoy your life, start by noticing tiny objects surrounding us.