In the screenplay I'm writing, one of the characters, a photographer, is obsessed with something called the golden ratio, which is also called phi, or sometimes the golden mean and other names. Though it is endlessly fascinating, I won't even explain what it is, because, well, I discovered this afternoon, when I was doing some research, that the golden ratio is what The Da Vinci Code is based on!
Okay, I will explain a little of it, only because it's so interesting. The golden ratio is the ratio where the relationship of the smaller portion to the bigger portion is the same as the relationship of the bigger portion to the whole. It is an irrational number (1.618 and on and on forever). But not only is it an irrational number, it is the most irrational number possible. It is the irrational number that is farthest away from a rational number.
And it appears over and over in nature; in the way seeds arrange themselves in a flower, the pattern of leaves on a stem, the way stalks of celery grow, the spiral of a snail shell, the chronology of rabbit offspring. Because of this, people in many cultures and religions have regarded it as a sacred and powerful number, close to the source of life. All kinds of religious symbols are based on it, from Vesica Pisces (the Christian fish) to the Flower of Life (a pattern made of interlocking circles which contains all the Platonic solids, and the Tree of Life, which is used in Kabbalah.
Renaissance artists were very into phi. It's used as a compositional device in paintings, sculptures, and buildings by Leonardo, Michelangelo, and others. Which I guess is why it figures in The Da Vinci Code. I didn't read the book, didn't see the movie. Wasn't interested.
It's good I found out now, before I'm too attached to it in my story. (I was a little attached.) I spent most of the rest of afternoon researching something else for my photographer character to be obsessed with. I think I have something better than phi. Well, not better than phi, but better for the character to be obsessed with.
The thing about phi is that the photographer was going to be covered with all these great tattoos of the various geometric symbols. There's an amazing 5-pointed star criss-crossed with hundreds of lines making it look like a crystal. Damn.