The tao of τ: bidding farewell to π?

"Pi" is absolutely amazing!

That was my reaction in grade school arithmetic class. I learned you didn't have to take a ruler and somehow measure the distance around a circle: You could simply measure the diameter and multiply by pi. C = πd, as our books presented it. It was an equation taught us long before we entered algebra, along with the even more miraculous equation for the area of a circle: A = πr².

The value of pi was usually given as 3.14, making our calculations easy. It wasn't until later -- maybe 7th grade -- that we learned that pi was an irrational number -- i.e., a number that couldn't be expressed as a fraction, and a number whose decimal expansion went on forever. Pi, therefore, could be expressed ever more precisely with each added digit, but no matter how many digits you added, it still wouldn't express with complete perfection the ratio between the diameter and the area of a circle.

Pi was an ideal, but an unattainable ideal: one that couldn't be described precisely with the numbers we had available.

People with strange mental abilities have memorized the decimal expansion of pi to incredible lengths. According to one source, a fellow from Pennsylvania named Mark Umile holds the record. In 2007, Umile recited from memory the first 15,314 digits of the pi expansion. I'm tempted to exclaim to this gentleman, "Sir, get a life!" -- but then, I have to ask, do I spend my days all that much more productively?

Anyway, this clutter of trivia has been prompted by a news story today, advising us that many mathematicians aren't happy with pi. It's not that they think it's incorrectly used, or that its value has been incorrectly calculated. They simply don't like using the diameter of a circle as the starting point for defining a universal constant.

The diameter is virtually never used in higher mathematics. All equations are expressed in terms of the radius -- one half of the diameter. So, once past grade school arithmetic, C = πd is often written C = 2πr. Consequently, mathematicians would feel more comfortable describing the constant in terms of the ratio between the circumference and the radius, rather than between the circumference and twice the radiuis.

Therefore, according to the news article, we should adopt 2π as our basic constant, and call it "tau," another Greek letter, one that is written "τ". Using tau as the constant is not only more elegant, they contend, but certain uses of pi that students begin running into once they get beyond fifth grade or so would be understood more intuitively if pi were replaced with tau. They hope to be reasonable -- they don't want to eliminate pi, they assure us, they just want to teach students to think in terms of tau, rather than pi. Start 'em off in grade school with C = τr, and their lives will be much easier as they get older.

This all sounds sort of reasonable, I suppose. It makes more sense than changing AD and BC to "CE" and "BCE." But these nice professors are explaining their views to a country whose citizens insist on seeing the world about them as one measured in miles, pecks, bushels, furlongs, quarts, and acres. You think they're going to adopt tau any more readily than they adopt liters instead of gallons? Good luck with that! I don't think they're going to buy it. Call it American exceptionalism, if you will. "That's not what they taught us when I was a boy," they'll exclaim. "Why fix it if it ain't broke?"

And the deal breaker: "If God wanted us to use tau, why did he give us pi?. I'll just stick with the good ol' time arithmetic, thank you much!"