Happy Tau Day 2015! Interest in the true circle constant (τ = C/r = 6.283185…) and The Tau Manifesto continued unabated this year, highlighted by a surge of attention on the “Pi [Half Tau] Day of the Century” (3/14/15). (Tau will have its revenge on 6/28/31—party at my place!) As one of the leaders of the “opposition”, I was invited to the Pi Day festivities at the Exploratorium in San Francisco—the organization that originally created Pi Day—but I was on vacation in Barcelona at the time and was unable to attend. (I know, rough life!) That the invitation was proffered in the first place is an excellent sign, though, as it serves as proof that even the Paladins of Pi recognize tau as a legitimate rival.
Here are some of the highlights since last year’s Tau Day:
I gave a well-received 15-minute talk at the BIL Conference (Los Angeles regional). BIL was founded as a sort of counter-conference to TED, and it was my pleasure to have the opportunity to prepare a condensed version of the original Tau Talk suitable for a general audience.
Inspired by feedback from the BIL talk, I’ve updated The Tau Manifesto with some new material, including added emphasis on an important observation: while there are infinitely many two-dimensional shapes with constant diameter, there is only one (the circle) with constant radius.
In case you missed it, tau/2 at Google evaluates to 3.14159… This got a big ovation at the BIL Conference talk!
In advance of Half Tau Day, Taylor University hosted the Indiana Mathematical Association of America Spring Section meeting, which featured the Great Tau/Pi Debate of 2015. Check it out, and decide for yourself who makes the better argument!
Robin Whitty continued to use tau freely in on his site Theorem of the Day. In fact, he’s concluded that tau is now well-known enough among his readers that it doesn’t require additional explanation, writing that “Four out of the last 10 theorems I’ve posted at theoremoftheday.org have featured tau and I’ve now given up adding (=2pi) on the assumption that everyone should know by now!”
Joseph Thiebes has created some tau-inspired merchandise at Tau Stuff, featuring several different tau pendant designs.
To improve his trigonometry course, mathematics teacher Phil Smith modified a couple of open-source math textbooks to use tau, and has posted the results online at Tau for Trigonometry. Thanks, Phil!
Jose Luis Garcia del Castillo from Fathom Information Design reports on the success of a second “tau fiesta” called ¡FiesTau!, which involved the “whole office playing Taupardy!, our own Jeopardy-inspired Tau quiz game written in Processing [a programming language that supports tau].” They’ve even released the source of Taupardy!, so now anyone can play! Fathom Information Design is also the maker of Peep in Tau, an app that lets you search for a number of your choice in the digits of tau.
Joseph Lindenberg shares an analogy he’s found useful in explaining tau to the uninitiated:
Using tau instead of pi makes math clearer, and thus easier to understand.
Using pi is like having a weird car whose odometer and speedometer display half-miles and half-miles-per-hour, while all the road signs show miles and miles-per-hour.
(The road signs of math are naturally in units of tau.)
So you constantly have to convert between what your car says and what the road signs say. 55 mile-per-hour speed limit? Make sure your speedometer needle doesn’t go over 110. But instead of nice round numbers like 55, imagine the sign says 68.7 miles-per-hour. So your speedometer needle shouldn’t go above… how much? Your trip odometer reads 35.7. So you’ve traveled… how many miles?
Sometimes you must multiply by 2. Sometimes you must divide by 2. And before doing either, you must always stop and decide which to do in this particular case. If you’re driving in heavy traffic, or bad weather, or you’re lost, you don’t want that distraction. The same is true if you’re lost while trying to learn trigonometry.
Thanks for all the support! For me, that makes for a very happy Tau Day.
Michael Hartl
Founder, Tau Day
Author, The Tau Manifesto
Happy Tau Day, everyone! This was a huge year for $\tau$, with continued adoption in programming languages and classrooms, appearances in a couple of prominent webcomics (xkcd & SMBC), and a big endorsement from Google. I also received an amazing parable about pi and tau from a precocious high-school student—seriously, give it a read.
Here’s a list of some of the highlights since Tau Day 2013:
$\tau$ made an appearance in an installment of the wildly popular webcomic xkcd, which proposes “pau” ($1.5\pi$) as a compromise between pi and tau. Be sure to hover over the image to see the bonus joke: “Conveniently approximated as $e+2$, Pau is commonly known as the Devil's Ratio (because in the octal expansion, '666' appears four times in the first 200 digits while no other run of 3+ digits appears more than once).” (UPDATE: An alert reader points to a discussion at explain xkcd that casts some doubt on one of the claims made in the bonus joke.)
$\tau$ made an appearance in an installment of the wildly popular webcomic Saturday Morning Breakfast Cereal (SMBC), which features a proud father bragging that his two-year-old child correctly calculated the “pi–tau constant” (i.e., 2). Be sure to click the big red button to see the bonus panel, in which the pi–tau constant appears as the comically obfuscated expression $K_{\pi\mathrm{-}\tau} = \sqrt{\left(e^{\ln (\tau/\pi)}\right)^2}$.
Google’s online calculator added support for $\tau$. For example, watch as Google correctly evaluates sin(τ/8).
Mathbreakers, a 3-D math exploration game, incorporated tau into its game world for teaching radian angle measure. Check out the Rainbow Radians demo video and the Mathbreakers Kickstarter campaign.
The Modula-2 programming language, originally developed by Niklaus Wirth and currently being revised by Benjamin Kowarsch and Rick Sutcliffe, now includes tau in its standard library.
The piClock iPhone & iPad app, which finds the current time inside the digits of mathematical constants, has added a “now with tau” badge and invites you to “double your pi-leasure and take a turn with tau.”
An 18-year-old high-school student from Oxfordshire, England, wrote a clever parody of $\pi$, published here with his permission: A Parable by Oliver Sayeed.
David Taylor of prooffreader.com published the über-nerdy and awesomely numerological post “Pi vs. tau: Ultimate Smackdown”. (Spoiler alert: tau wins.)
Scientific American published the excellent article “Why Tau Trumps Pi” by Randyn Charles Bartholomew. The URL still reveals the original title, “Let’s Use Tau—It’s Easier Than Pi,” and I can’t believe I didn’t think of the tagline “Tau is easier than pi” myself. Brilliant!
I’ve been gratified by the continued enthusiasm for $\tau$ since the launch of The Tau Manifesto in 2010. I especially appreciate the support of Robert Palais, Joseph Lindenberg, Peter Harremoës, Robin Whitty, Vi Hart, and all the tauists who’ve reached out about $\tau$ in the past four years. Here’s to another great year ahead for $\tau$!
—Michael Hartl, Tau Day 2014
It’s been a big year for $\tau$. When I launched The Tau Manifesto back on Tau Day 2010, I hoped that $\tau$ might strike a chord, but its popularity has exceeded my wildest expectations—due in large part to the efforts of the many ardent tauists who picked up $\tau$ and ran with it. Now three years on, activity surrounding both the constant and the notation continues apace. In honor of Tau Day 2013, I’ve listed below some of the highlights from the last year. Enjoy, and Happy Tau Day!
Michael Hartl
Founder, Tau Day
Author, The Tau Manifesto
Note: I’d like to thank Joseph Lindenberg, Robert Palais, Robin Whitty, and Peter Harremoës for their help in compiling this list.