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## Pi Day Is Coming — But Tau Day Is Better241

PerlJedi writes "A few months ago, a Tweet from Randal Schwartz pointed me to a YouTube video about 'Triangle Parties' made by Vi Hart. My nerdiness and my love of math made it my new favorite thing on YouTube. Now, with Pi Day coming up later this week, I thought it would be an appropriate time to point people to another of her YouTube videos: Pi is Wrong. The website she mentions at the end, Tauday, has a full explanation of the benefits of using Tau rather than Pi. Quoting: 'The Tau Manifesto is dedicated to one of the most important numbers in mathematics, perhaps the most important: the circle constant relating the circumference of a circle to its linear dimension. For millennia, the circle has been considered the most perfect of shapes, and the circle constant captures the geometry of the circle in a single number. Of course, the traditional choice for the circle constant is pi — but, as mathematician Bob Palais notes in his delightful article "Pi Is Wrong!", pi is wrong. It's time to set things right.'"
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## Pi Day Is Coming — But Tau Day Is Better

• #### Cant eat a slice of Tau to celebrate. (Score:5, Insightful)

on Monday March 12, 2012 @02:12PM (#39329047)
Thing is, we like pie. Being able to eat a Pi sized slice of Pi at 1:59 on 3.14 is a geeky excuse to consume treats.
• #### Re:Breaking derivatives (Score:2, Insightful)

on Monday March 12, 2012 @02:25PM (#39329287)

No, it doesn't. Just using a different scale (x = 2y).

• #### tau is wrong (Score:2, Insightful)

on Monday March 12, 2012 @02:32PM (#39329423)
Division is harder than multiplication. Given the choice between sometimes multiplying by 2, and sometimes dividing by two, we should pick the constant that forces the multiplication. Also, e^(pi * i) is nicer than e^((tau / 2) * i).
• #### Re:Cant eat a slice of Tau to celebrate. (Score:5, Insightful)

on Monday March 12, 2012 @02:45PM (#39329667) Homepage Journal

With Tau, you can have two pies.

• #### Re:Triangle Panties (Score:4, Insightful)

on Monday March 12, 2012 @03:03PM (#39329925)

It is? Like what? There's a lot of greek symbols that are used for different things, so you have to look at what domain you're in before you make any assumptions about their values. This also applies to latin symbols.

Quick: what is i? Well, that depends. If you're a mathematician, it's the square root of -1. However, if you're an electrical engineer, the answer is the AC current. In EE, j is the square root of -1. Omega, theta, tons of symbols like these are reused in different domains for different things.

Offhand, I don't remember tau being used for anything else in mathematics (specifically geometry), so it seems as good a symbol as any. According to Wikipedia, there's a handful of mathematical uses for tau already, but they seem pretty esoteric (or obsolete, in the case of the golden ratio, which more commonly uses phi). It is used for a bunch of things in physics and biology, but those are different domains, so that's pretty irrelevant. You don't use pi (the circle constant) much in biology either, I imagine.

However, there are some greek letters that are barely used, so maybe one of those would be better. Upsilon, for instance, only has one use listed in Wikipedia's list of greek letters used in math, science, and engineering, to represent an elementary particle. Only physicists would ever see that (I don't think I ever saw that in college, as I was a EE major), so maybe that'd be a better choice than tau.

• #### Re:Triangle Panties (Score:5, Insightful)

on Monday March 12, 2012 @03:07PM (#39329975) Homepage Journal

And, I think it's perhaps a little wrongheaded anyway. The area of a circle is pi*r^2. That'd become tau*r^2/2... You took the 2 out of one place and put it in another. And it does nothing for spheres: Volume = (4*pi*r^3)/3 = (2*tau*r^3)/3; Surface area = (4*pi*r^2) = (2*tau*r^2).

And besides, tau's already claimed as the "time constant" variable, so n'yah!

• #### Re:tau is wrong (Score:5, Insightful)

on Monday March 12, 2012 @03:50PM (#39330575)

Sure there is: e^(tau * i) + 0 = 1.

Hey, it's really not any more ridiculous than "... + 1 = 0".

• #### Re:tau is wrong (Score:5, Insightful)

on Monday March 12, 2012 @08:17PM (#39333833)

Umm, no!

e^(pi*i) = -1 implies e^(tau*i) = 1

e^(tau*i) = 1 does not imply e^(pi*i) = -1

The tau version follows from the pi version. The pi version does not necessarily follow from the tau version, because the tau version would still be true if e^(pi*i) = 1.

So the tau version is missing some very important information.

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