Pi Day 3.14= π

Amy from messymiddle.com 

Today is Pi Day, celebrated all over the world. This is one of those things that almost everyone agrees upon and an idea like that is worth celebrating in these crazy times.  The number for π is 3.141592, so you can see how last year’s π day 3.14.15 at 9:26:53 was really a big deal, called  by many the Ultimate Pi Day.  But this year's is worth celebrating again. Math is both so real and unreal, constant and changing, but π is not.  It is always the ratio of the circumference of the circle to its diameter—big circles, tiny circles, and medium circles, all circles.

The symbol for Pi is π, the sixteenth letter of the Greek alphabet.  It is easily found on the symbols insert page of Word and probably most other word processing systems.  Guess what, the ancient Greeks did not use the symbol π to signify the ratio of a circle’s circumference to its diameter.  Nor did the Arabs, Chinese, or the Romans. It was more than two thousand years after Archimedes studied circles that π began to be used.  And it was in the year 1706 that William Jones first used π in its modern understanding.  But Jones’s use of it did not catch on.  It was Leonhard Euler, who really got the symbol going.  In 1736, after shifting around in the use of π and other Greek letters, Euler began using π in his papers and letters to denote the ratio of circumference to diameter.  This time it caught on.  Johann Bernouli who had been using a different symbol soon started using π in his correspondence with Euler.  And then when Euler used it in his Introductio in analysin infinitorum published in 1748, well as they say, the rest is history. 

But interestingly, it is also Albert Einstein’s birthday—March 14, 1879, and today would be his 137^th birthday.  137 is itself a prime number and I found a curious fact about 137 on the web this morning.  It is “the only known primeval number whose sum of digits equals the number of primes "contained." 137 is the largest prime factor of 123456787654321. The reciprocal of the fine-structure constant of electromagnetism is close to 137.”  Now that is really something, isn’t it?

So today we can celebrate π day along with the birthday of one of the greatest geniuses of the 20^th century.  It’s raining and overcast here in New York, but I am smiling and seeing the sun—after all it is π day and that only comes along once a year.