# Bye Bye Pi — It’s Tau Day Today (VIDEO)

Move over, pi, it’s tau’s day today.

Yes, forget everything else you’ve heard. The big news for June 28 is that it’s is Tau Day, whose organizers, celebrators and assorted others say that a constant called tau, τ (the Greek letter “t”) should take over from pi, π (the Greek letter “p”).

Tau is worth about twice as much as pi, about 6.28 — hence today being Tau Day — and, according to mathematicians, it makes more sense and is easier to use when making calculations. Says self-proclaimed anti-pi propagandist, educator and former theoretical physicist Michael Hartl:

“When I say pi is wrong, it doesn’t have any flaws in its definition – it is what you think it is, a ratio of circumference to diameter. But circles are not about diameters, they’re about radii; circles are the set of all the points a given distance – a radius – from the centre.”

By defining pi in terms of diameter, he said, “what you’re really doing is defining it as the ratio of the circumference to twice the radius, and that factor of two haunts you throughout mathematics.”

Bob Palais of the University of Utah gets the credit for first saying that “pi is wrong” in a 2001 Mathematical Intelligencer article. Dr. Hartl authored the Tau Manifesto to make tau’s case and also created Tau Day. He notes the passion of tau adherents:

“What’s amazing is the ‘conversion experience’: people find themselves almost violently angry at pi. They feel like they’ve been lied to their whole lives, so it’s amazing how many people express their displeasure with pi in the strongest possible terms – often involving profanity.

“I don’t condone any actual violence – that would be really bizarre, wouldn’t it?”

I have to say hearing that pi — 3.1415926…, the ratio of any circle’s circumference to its diameter —  could be pushed out of the way by another constant was a bit of a shocker. Hours in mathematics class learning formulas, working through proofs and making all kinds of calculations (something I have to say, I enjoyed — I was quite good at math until I hit calculus) have left me thinking that learning about pi is de rigueur.

Here’s a video about how what tau sounds like:

Here’a video about Daniel Tammet, who recited pi from memory to 22,514 decimal places in a time of 5 hours, 9 minutes on March 14, 2004, a real homage to pi whose days, it seems, could well be numbered.

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Photo by the author.

### 31 comments

Wait. What? Did it say Schrödinger on that piano??

I'd rather eat cake, anyway.

Very interesting tune tho. I found it rather relaxing until he got too many instruments going.

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that's all good for the circonference, but what about the surface?
What about π by the square of r?

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Glad I don't have to learn geometry again.

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Glad I am not the only math whiz who hit the wall at calculus! After watching the vids, and rereading, I get it though: "circles are not about diameters, they’re about radii". Never would have thunk that, but it is true.

Besides, aren't there better things to do with one's time then remember such hideously infinte numbers? I gots better fun things for my brainy! But hey - whatever floats your boat!

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Thank you for the article.

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thanks for sharing.

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Yea Tau! Day!
But will I remember next year?

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Thanks for this great article.

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goodbye pi pie pai but i have to say this one thing: "at my age, these "changes can make an aging hippy/yippy CRAZY"..... have a good day eating PIE................

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Interesting, thanks! Does these mean there'll be new formulae....

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