The golden ratio (golden number, golden section, and other names) is an amazing principle that happens normally in nature. Nautilus seashells, butterflies, sunflowers, pine cones, pineapples, and countless other plants and animals have designs that can be mathematically described by the golden ratio. I think it is also particularly interesting that the human body was put together following the golden ratio. The placement of the eyes, the ears, and the lips are all on golden ratios. The first knuckle of your fingers is on the golden ratio of the tip to the second knuckle and the second knuckle is on the golden ratio of the entire length of that finger.
In architecture, the pyramids are a perfect example of the golden ratio as is the Greek Parthenon and Notre Dame Cathedral. Renaissance artists called it the Golden Proportion and the Last Supper and the Mona Lisa are examples where da Vinci used strict usage of the golden ratio. The vessels of the Ming and other Chinese dynasties placed the widest width of their vases exactly at the golden ratio of the height of the vessel.
It wasn't until the 14th century that an Italian mathematician named Fibonacci discovered the mathematics behind the ratio. Today, those formulas are used in nearly every technology. One of my favorite uses of Fibonacci ratios is in stock and commodity trading.
Jeff is right, though, that the use of the golden ratio in woodturning is completely optional and thank heavens that every vessel doesn't use the ratio or the turnings would all start to look alike. Using the raio doesn't make the vessel 'right' or 'wrong', necessarily. But just as putting the horizon in the vertical center of a photograph is just plain wrong, a vase with the widest part at the vertical midpoint is equally wrong. In photography, you'll often hear of dividing the height and width into thirds and the intersection of the lines is where the points of interest should be located. The 'thirds' is simply a quick way to get close to the golden ratio.
I will try to make some time to do a tutorial on how the Golden Ratio can be used in designing a vessel that uses ratios to determine height vs width, placement of elements, sizing the mouth and base, and any other things I can think of.
In the meantime, if you'd like to learn more about the Golden Ration, you can reach a great site by
CLICKING HERE.
One good thing about using the Golden Ratio is that if your vessel is ever being critiqued, the individual doing the review has been selected because of a history of good design practices and that would almost always imply that they have a good understanding of the Golden Ratio. You won't have to tell them that you used it - they will automatically recognize it.
Lloyd