Golden Ratio

Some of the greatest mathematical minds of all ages, from Pythagoras and Euclid in ancient Greece, through the medieval Italian mathematician Leonardo of Pisa (Fibonacci) and the Renaissance astronomer Johannes Kepler, to present-day scientific figures such as Oxford physicist Roger Penrose, have spent endless hours over this simple ratio and its properties. But the fascination with the Golden Ratio is not confined just to mathematicians. Biologists, artists, musicians, historians, architects, psychologists, and even mystics have pondered and debated the basis of its ubiquity and appeal. In fact, it is probably fair to say that the Golden Ratio has inspired thinkers of all disciplines like no other number in the history of mathematics.
Mario Livio, The Golden Ratio: The Story of Phi, The World's Most Astonishing Number

The golden ratio is an irrational number, approximately 1.6180339887. Mathematician Mark Barr proposed using the first letter in the name of Greek sculptor Phidias, phi, to symbolize the golden ratio. The Golden Ration is often reffered to as Phi.

This ratio can been seen throughout nature and in acient greek design.

File:Divina proportione.png
File:Divina proportione.png