Phi AKA the Golden Ratio AKA 1.61803398875
Ancient Greeks noticed that when a line is divided into two unequal sections, the ratio of the longer part to the shorter is in the “golden proportion” if it equals the ratio of the whole line to the longer section.
First dubbed the “divine proportion” by a 15th-century friar who argued that it was the most esthetically pleasing ratio, by the 20th century the number–now called phi–had developed a cult following among scientists and amateurs for its reported appearance in nature and art. Spirals based on the ratio can be seen in microscopic protozoa, mollusks and galaxies of stars, as well as the arrangements of petals in a rose or seeds in a sunflower. The architect Le Corbusier deliberately used it in his designs, as did artists like Salvador Dali and German Renaissance painter Albrecht Durer.