Saturday, May 25, 2013

What is the Golden Ratio?

By George Smith


Mathematicians and artists have throughout modern history been fascinated by a special proportion known as the golden ratio, or golden section as it is also called. The special feature of this proportion is that if you divide a line into a larger and smaller section, A and B, then A is to B as the whole line is to A. Numerically it is about 1: 1.618. The golden ratio has been used by many architects as a basis for their buildings, as well as by many painters and even musicians.

No other number in the history of mathematics has inspired thinkers of all disciplines like the golden ratio. It has fascinated for at least 2.400 years since Pythagoras and Euklid in ancient Greece. Amongst the outstanding thinkers, who have pondered the golden ratio, we can mention Leonardo of Pisa, Johannes Kepler and the present day physicist Roger Penrose. It has fascinated biologists, artists, musicians, architects, psychologists and occultists alike. The 12'th century mathematician Fibonacci discovered what is today known as the Fibonacci sequence: 1, 1, 2, 3, 5, 8, 13, 21, etc. in which each new number is the sum of the two preceding. As you continue this sequence, it will accurately reach the golden ratio. One peculiar figure is the pentagram: every segment of it stands in a golden ratio relationship with some other line of the figure.

In honor of Phidias, the great Greek sculptor from about 400 BC who used the golden proportion extensively in his sculptures, the golden proportion is now commonly known as Phi, the first letter of Phidias' name. The golden ratio has also been known as the divine proportion since 1509, when Luca Pacioli published a three volume book on the golden ratio entitled "De Divina Proportione". Pacioli saw religious significance in the proportion, hence the title of his book. The book was a major influence on artists and architects for hundreds of years.

In modern times the Swiss architect Le Corbusier is famous for his use of the golden ratio. He saw the ratio and the Fibonacci sequence as representing a mathematical order of the universe, and he described them as: "rhythms apparent to the eye and clear in their relations with one another. And these rhythms are at the very root of human activities. They resound in man by an organic inevitability, the same fine inevitability which causes the tracing out of the Golden Section by children, old men, savages and the learned."

Painters, such as the 17'th century master Vermeer, have used the golden ratio extensively, so did a modern master like Salvador Dali. Dali adored Vermeer, by the way. The golden ratio and the Fibonacci sequence have also been used by composers. The modern composer Bartok, for example, based the xylophone progression in "Music for Strings, Percussion and Celeste" on the Fibonacci sequence 1, 2, 3, 5, 8, 5, 3, 2, 1. Similarly Satie and Debussy are known to have used the golden ratio as a basis for some of their compositions.

One also finds the golden ratio in nature. The arrangement of branches along the stems of plants, for instance, often follows the golden ratio.




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