Fibonacci Sequence Day: November 23

Did you know that yesterday was Fibonacci Sequence Day?

Leonardo Bonacci with graphics of his Fibonacci Sequence and the Golden Ratio | Credit: National Today

The poetry of mathematics manifests everywhere in nature, but few numerical patterns are more common than the Fibonacci Sequence. First described in 1202 by mathematician Italian Leonardo Bonacci (Fibonacci is a shortening of filius Bonacci or “son of Bonacci”), the concept involves adding 1 and 1 together, then doing the same for every successive pair of numbers.

It starts like this: 1+1 = 2, 2+1 = 3, 3+2 = 5, 5+3 = 8 and so on. Fibonacci Day is celebrated annually on November 23 because the date's numbers - 11/23 - correspond to the first numbers in the Fibonacci sequence: 1,1,2,3.

However, at the time Fibonacci was working, numbers in Europe were usually expressed by using unwieldy Roman numerals. To simplify things, Fibonacci also proposed adopting the Hindu-Arabic numerical system based on the symbols 0 through 9. Although he died sometime between 1240 and 1250, his Arabic numeral suggestion ultimately became the norm across Europe by the 15th century.

Once people became aware of the sequence, it started showing up everywhere. Nature is full of Fibonacci patterns, from DNA to hurricanes, leading some to dub the Fibonacci sequence “nature’s secret code".

Whilst the Fibonacci Sequence is a rudimentary idea, the wider implications are profound. It’s also directly related to another concept known as the Golden Ratio (believed to create visually pleasing and harmonious compositions, and has been used in famous works like the Parthenon and by artists like Leonardo da Vinci) that appears in several natural phenomenon including tree growth, the Milky Way galaxy’s spiral arms, seashells, and many others. Without the Fibonacci Sequence there even wouldn’t be a practical way to design today’s programming algorithms, says Popular Science.

Although technically not an example itself, November 23 provides the most appropriate day to celebrate the famed thinker for his contributions to mathematics.

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