七十二律是誰創?有數學原理proof?

據說是愛因斯坦所創：

Rule of 72

The compound interest rule of 72 was discovered by Albert Einstein. Referring to compound interest, Albert Einstein is quoted as saying: "It is the greatest mathematical discovery of all time."

Albert Einstein (1879 - 1955) called the compound interest rule of 72 the 8th Wonder of the World - It can work for you, or against you. When you invest it works for you. When you borrow it works against you!

Full Article:
http://www.mortgagesaver.org/albert-einstein%27s-compound-interest-rule-of-72.htm

至於數學原理，可以參考這裡：
http://www.moneychimp.com/features/rule72_why.htm