pi or what

[thundercrack]

can someone tell me what that number is that is a natural occurring feature, as mentioned in the divinci code, petals on a sunflower, measurement of pyramids and other things which I have no doubt you will enlighten me with. I thought it was pi, but obviously that is circumferance and diameter calculations.
thanks, alf.

[behappy87]

It's the golden ratio, given by the greek number phi. It comes up in a lot of places...in art it is often used for canvas sizes (i.e. where one side is length one, and the other phi), as it is said to be aesthetically pleasing...as for the petals on a sunflower thing - that's fibonacci's sequence ( 1, 1, 2, 3, 5, 8, 13, 21, 34...you calcule the nth number from adding the (n-1)th and (n-2)th)...fibonacci's sequence and the golden ratio are very closely related, each term in the sequence can be expressed in an equation involving phi...here are some links if my explanation wasn't very good...

http://en.wikipedia.org/wiki/Fibonacci_number

http://en.wikipedia.org/wiki/Golden_ratio

Oh, and the actual number is 1.6180339....., or exactly one plus square root of 5 all over 2.

[jake-the-peg]

Facts and myths about the golden ratio:

http://www.sciencenews.org/articles/20070630/m athtrek.asp