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## Pi is (still) wrong

See this video, by Vi Hart:

This link was passed on to me by my friend Marcello. I’ve been bold enough to make up words such as eigenaxis and eigenpoint, but it takes real courage to suggest redefining π, even when you’re right!

After seeing the video, you can go here and here to learn more about what is being proposed.

Don’t click on comments until you’ve seen the video. Ms. Hart does a better job presenting the proposal than any of us can.

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• Anonymous

There was a little flutter of activity after Marcello privately sent a few of us this link. Nick Cox wrote, “I love this stuff. I watched the video and then stayed up late browsing the links. I am going to look for Hoyle’s 1962 book.” He also suggested Stata should do its bit by adding tau() and c(tau) to accompany the already existing pi() and c(pi), but I don’t know whether he was serious.nnMy contribution was,nn”At first, I thought she was going to go in the physics direction, and say that in a properly laid out university, π would be 3. With a little curvature, the supreme being could have arranged that. What was S/He thinking?nn”But instead it went in a unexpected direction for me and I must say, she’s right. From now on, I’m using tau.nn”Mathematically speaking, she’s also right about eiτ = 1 being a substitute for eiπ = -1 Still, I’ll miss it because both of the popular imaginary units were in it, i and -1. I’ve always argued, and I’m not alone, that -1 is every bit as imaginary as sqrt(-1), as neither one really exists, and both exist in mathematics solely as a contrivance to make calculations, the results of which always come back to the real numbers, by which I mean the positive ones, and zero. That’s real with a lowercase r.nn”Concerning Reals with a capital R, I’ve never been convinced that they are real, even the positive ones. This idea about there being an infinite number of numbers between any two numbers strikes me as not only unreasonable, but likely not true. I suspect that physicists will ultimately discover that space itself is discrete. We’ll lose calculus, but I always found its proofs slippery. And anyway, I’d enjoy the reversal of roles. Right now, the calculists claim truth and they cast people who worry about calculable functions, like me, as producing approximations. If space is discrete, they’ll be the ones producing approximations. And tangents will be secants.”n

• Nick Cox

I’d put the main point in another, slightly different way. nnNo one is proposing to re-define pi. nnPi remains exactly what it was. The proposal is just to use 2 pi, to call it tau, because often that makes matters simpler and easier to understand.nn

• Andy

I have pi tattooed on my back. The idea was i couldn’t get tired of it because no matter what changed, pi was constant. But this video and apparently this movement are obviously spot on. I kind of wish my tattoo was of tau. I am a long-time math tutor and you just rocked my world. Thanks.

• Op_cris

interesting! and a very little observation – a flaw in the beginning of this video (0:15), the notation in ratio is put wrong, it is b/a of course – she correctly states the definition, just noted it wrong

• Jpvfiu

she must have tiger blood in her veins…..Pi-winning!!

• “No one is proposing to re-define pi.”
At least, not since the attempt by the Indiana state legislature in 1897 ( http://www.agecon.purdue.edu/crd/localgov/second%20level%20pages/indiana_pi_bill.htm )

• Nick Cox

Several people are still working away in a campaign: see lots of good detail in http://www.harremoes.dk/Peter/Turnpage1.pdf
which at this writing was dated March 3, 2012