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Friday, March 14, 2008

The Pi Day

In the blogger's world, a date is usually just something to identify the beginning of a new blog. The fact that 3/14 is known as the International Pi Day just came to my attention. As someone who fancies himself always interested in math things, I have to add this post to honor this day though there's not much direct connection between pi and freaque waves. Of course, being in the late afternoon now I missed the Pi minutes which is 1:59 am on 3/14 (1:59 pm will do, but that's 13:59 for many). Anyway, today is the 20th anniversary of the celebration of Annual International Pi day.

Additionally scientists generally remember that this day is also the birthday of Albert Einstein. Not much of a phyicist myself, this is of less significance to me but still worth to mention while I am at it.

What's the big deal of of pi? Well, multiply pi to the diameter of a circle gives the circumference and multiply pi to the square of the radius gives the area of the circle which are the things we memorize since elementary school days. This interesting site here reminded me that Pi was discovered by Archimedes in the 2nd century BC and this old joke: "Pi r-squared? No, pie are round. Cake are squared."

Have a happy Pi day! (In a few hours, it will be "Beware the Ides of March!")


It is of interest to take a look into the history. It may not be entirely true to say that Archimedes "discovered" Pi. According to the NOVA site:
In Archimedes' day, close approximations of pi had been known for over 1,000 years. An Egyptian document dated to 1650 B.C., for example, gives a value of 4 (8/9)2, or 3.1605. Archimedes' value, however, was not only more accurate, it was the first theoretical, rather than measured, calculation of pi.
So Archimedes was the first one to provide more accurate value for Pi. The efforts to obtain more and more accurate Pi value have been continued ever since as this site show:

Ptolemy (c. 150 AD)3.1416
Zu Chongzhi (430-501 AD) 355/113
al-Khwarizmi (c. 800 ) 3.1416
al-Kashi (c. 1430) 14 places
Viète (1540-1603) 9 places
Roomen (1561-1615) 17 places
Van Ceulen (c. 1600) 35 places

I was particularly interested in the not so very well-known, but a great Chinese mathematician nevertheless, by the name

my prefered translation is Tsu Chung-Tze, which they say "about whom next to nothing is known." But he was well accomplished in mathematics, astronomy, and mechanical devices among other things during the Northern and Southern Dynasties period in Chinese history. I found from this site here, that there was some indication on how it was done in getting the value equivalent to Pi by Tsu in the 5th century A.D. China:

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