Happy Tau Day 2019, everyone! On this June 28 (6/28 in the American calendar system), thanks for joining me in the annual celebration of the true circle constant, $\tau = C/r = 6.28\ldots$
A special thank-you goes out to anyone wearing an Official Tau Shirt today. You can post pics or any other tau-related material on Instagram #TauDay or Twitter #TauDay.
The tau news I’m most excited about this year is a full translation of The Tau Manifesto into Spanish by tau supporter Juan Guijarro Ferreiro. You can find the result, El Manifiesto Tau, on the Tau Day website. ¡Muchísimas gracias, Juan!
Some pi partisans occasionally brag about how “Pi Day” (3/14) is the birthday of Albert Einstein, so it’s perhaps worth noting that Tau Day is the birthday of another great 20th-century physicist: Maria Goeppert Mayer, who won a Nobel Prize in Physics for her groundbreaking work on the nuclear shell model.
Long-time tau supporter Joseph Lindenberg has pointed out that Tau Day is also the birthday of famed entrepreneur and literal rocket scientist Elon Musk.
On this 9th annual Tau Day, please join me in wishing happy birthday to Professor Goeppert Mayer and Mr. Musk!
Tau Manifesto reader Jason Brown passed along a delightful tau essay that I’d somehow missed all these years: “My Conversion to Tauism” by Stephen Abbott, which appeared in the magazine Math Horizons in 2012. Professor Abbott is a mathematician at Middlebury College and author of the outstanding textbook Understanding Analysis, making his endorsement especially gratifying. I particularly appreciated this line from the essay:
“The Tau Manifesto” is an entertaining read, so entertaining in fact that you don’t immediately notice how utterly compelling it is.
Thanks, Professor Abbott! I’m glad you liked it. :-)
My friend Alex Wood reports on an exchange involving an Internet trivia game:
My girlfriend, reading me trivia questions: “According to a manifesto written by Michael Hartl—”
Me: “Tau”
You’re internet trivia famous, man 😂
Continuing a theme set by xkcd & SMBC, on October 13, 2018, the comic strip Sally Forth prominently featured tau:
Thanks to alert reader and long-time tauist Skona Brittain for the heads-up!
Speaking of SMBC, tau also makes a cameo appearance in the strip “Mega-Pi” about a proposed mathematical constant equal to two million pi (i.e., one million tau).
The popular Unity video game engine now includes tau as a pre-defined constant, thereby joining languages such as Python, Processing, and Modula-2. (Still waiting for Ruby to join the party, though!)
Finally, here’s a short summary of some of the high-profile celebrations of Tau Day from last year.
Joseph Lindenberg passed along this report of the Museum of Science in Boston holding a Tau Day fundraiser, with a benefactor offering to match donations. (The campaign is from last year, but appears to be active, so I think you can still donate if you like.)
The Museum of Science also sponsored tau-themed yoga classes at 6:28, both a.m. and p.m.!
Speaking of the Boston area, the official MIT Twitter account sent out a tweet in honor of Tau Day:
Thanks, MIT! Now if only either of my own almae mātrēs would show tau such love…
The hugely popular science-themed YouTube channel SciShow (5.7 million subscribers as of this writing) featured an outstanding “Happy Tau Day!” video. Thanks to SciShow for the support!
Swiss open-access academic publisher SciPress ran a Twitter poll on Pi vs. Tau in which, appropriately enough, tau was around twice as popular as pi!
(I neither retweeted nor voted in the poll, so that’s about as unbiased as a Twitter poll can get!)
That’s it for this year! Thanks again for all the enthusiasm and support for this quirky little project.
Happy Tau Day, everyone!
Happy Tau Day 2018, everyone! Thanks for joining me in this annual celebration of the true circle constant, $\tau = C/r$.
I hope you’re all prepared with twice as much pie. 😋🥧🥧
As is my usual custom, I’ve prepared a State of the Tau update summarizing the various tau happenings over the past year.
I’ve substantially revised and updated “Getting to the bottom of pi and tau”, especially the section on hyperspheres, including a brand-new section on recurrences. It’s more mathematically challenging than the rest of The Tau Manifesto, but of course this can be a feature. Go ahead and take a look if you’re in the mood for a challenge!
June 28, 2017 proved to be the most eventful Tau Day since the original Tau Talk in 2011. First of all, I was hosted by Googler Kevin Oberlies and the other gracious folks at Google’s Los Angeles office as part of their “Talks at Google” series. The result is a beautiful HD update to the 2011 version of the talk:
After finishing the presentation, I and some fellow tauists adjourned for lunch, where the Google dining staff had prepared a special surprise for us—tau-themed cupcakes!
Perhaps the greatest highlight of the day was finally meeting Bob Palais, author of the original “π Is Wrong!” article that planted the seed for The Tau Manifesto back in 2001. Bob attended the talk at Google and then came to a Tau Day party I hosted that evening. Here we are in our matching Tau Shirts:
We celebrated late into the night with twice as much pie. Thanks to everyone who made Tau Day 2017 so memorable!
In March 2018, just before Half Tau Day, I was pleased to learn (via Joseph Thiebes) about a fun new tau meme making the rounds online. Created by mathematician Diego Vera, it’s titled “The Virgin Archimedes’ Constant vs. The Chad Hartl–Palais Constant”, and is based on the famous Virgin vs. Chad meme template. Here it is, lightly edited to keep in line with Tau Day’s family-friendly G rating:
You can find Diego’s original version (rated PG for language) here. Thanks to Diego for the great meme work, and to Joseph for giving me the heads-up about it!
Did you know that the great Leonhard Euler almost settled on using $\pi$ to mean $C/r$ instead of $C/D$? Oh, how much confusion that would have spared us! Check out this fascinating video on the subject:
Recognition of tau as the true circle constant continues to grow. OG tauist Wyatt Green sent this encouraging field report:
I just wanted to report to you that my dad emailed me this link: “Forget Pi Day. We should be celebrating Tau Day.”
Tau Day has crossed the barrier from esoteric geek conversation to links that family members forward to each other. I feel this is a special accomplishment—a breakthrough into the mainstream.
I also learned via a tweet from Sarah Jeong about an article at The Verge called “Stop celebrating Pi Day, and embrace Tau as the true circle constant”. It’s exciting to see this idea taking root!
Here are the full attributions for reference:
Finally, as usual I’ve relaunched sales of the Official Tau Shirt for a limited time (through Monday, July 2 at 8 p.m. Pacific). It’s an international phenomenon! For example, Johann Swanepoel from South Africa writes:
See attached, me proudly wearing my Tau shirt at the weekly parkrun in George, Western Cape, RSA.
Thanks to Johann and all the other tauists around the globe for making Tau Day and The Tau Manifesto a continuing source of amusement and joy!
Happy Tau Day!
Till next year,
Michael Hartl
Founder, Tau Day
Author, The Tau Manifesto
Happy Tau Day, everyone!
We’ve come a long way since the launch of The Tau Manifesto in 2010, and this year saw continued progress and interest in τ, the true circle constant.
In case you’re short on time, here are three quick action items:
There are many ways to celebrate Tau Day, of course, and I hope you’re having fun.
I’m celebrating this year by giving an updated version of the original Tau Talk at Google’s Los Angeles office in beautiful Venice, California. Joining me there will be original “π Is Wrong!” author Bob Palais as a special guest!
The Google event is closed to the public, but (as noted in the action items above) anyone in the Los Angeles area is welcome to join me and fellow tau enthusiasts for the official Tau Day 2017 party.
The plan, as usual, is to eat twice as much pie!
Just in time for Tau Day 2017, Scientific American has published “The Tao of Tau”, an exploration of the use of the letter tau in science, engineering, and mathematics. The article opens with an acknowledgment of the true circle constant:
“It is lamentable that there’s no famous dessert named ‘tau,’” Michael Hartl told me recently at a sunny, stylish café in Venice, California. He reluctantly admitted that pi, the constant approximately equal to 3.14, has this one advantage over tau, a number he introduced to replace it.
Read the whole thing there. Congratulations to author Elizabeth Landau on a job well done!
One of the most exciting tau events this year involves the Python programming language, one of the most popular and powerful languages in use today.
Although nowadays I’m better known for my contributions to the Ruby community, Python was actually the first programming language I really loved.
It is therefore with great pleasure and pride that I announce the inclusion of tau in the latest version of Python. That’s right—after some lively debate, the BDFL of Python, Guido van Rossum, decided to include tau as part of the official math library in Python 3.6:
>>> from math import tau
>>> tau
6.283185307179586
Go forth and wield tau, O brave Pythonistas!
Another welcome tau contribution came via the son of reader Bobby Cieszki, who created a haunting parody of Kid Cudi’s song “Day ‘N’ Nite” called “Tau N Pi”. Give it a listen—it’s really quite extraordinary.
Last year I mentioned that two breweries (Hawkshead Brewery in the UK and Crooked Stave here in the US) had collaborated to bring the world Key Lime Tau beer. Sounds great, right?
Alas, I soon discovered that it is rather hard to come by.
Well, tauist Richard Soderberg took this as a challenge. He diligently tracked down a vendor, and procured for me a generous supply.
Verdict: Deliciously sour, and worthy of its name!
Thanks, Richard!
Tom Magliery reports on an art project he created involving a collage of numbers—found in the wild, so to speak—assembled to form the digits of tau:
Cool!
On Pi Day (or, as I prefer to call it, Half Tau Day), Los Alamos National Labs acknowledged tau in its Bradbury Science Museum newsletter article called “Celebrate Pi Day on March 14 (3.14)”:
Pi and controversy (Didn’t see that coming, did you?)
Back in 2001, Bob Palais, a math professor at the University of Utah, wrote an opinion piece for The Mathematic[al] Intelligencer called “π is Wrong!” Apparently, the counterargument against pi is that it is often used as 2π for equations, so why not just use 6.28 instead of 3.14?
That call reemerged again in 2010, when Michael Hartl wrote a book [sic] called The Tau Manifesto making a similar argument and offering up the name of “tau” as the shorthand of 2π or just τ as its symbol.
He’s called for an annual Tau Day on June 28 (6/28 on the American calendar) to raise awareness of the tau concept.
In case you don’t have enough interest to absorb the contents of his book [sic], Michael’s website includes two videos explaining the concept of tau in both short (14 minutes) and long (51 minutes) versions to bring you up to speed.
Alert reader Wouter Vink passed along this remarkable sighting of tau in an article from a Dutch newspaper:
I can’t read Dutch, but this has to count as a good sign. Tau continues to be an international phenomenon!
Tauist Ryan Brancheau has launched a tau Kickstarter to make European-style oval magnets with 6.28 in the middle and further digits around the side. Let’s see if we can get Ryan’s project to tip!
Finally, as usual I’ve relaunched Tau Shirt sales as part of the Tau Day celebrations.
To paraphrase Yogurt from the movie Spaceballs:
Merchandising! Merchandising! Where the real money from the Manifesto is made!
Supporting tau is a labor of love, of course, and it isn’t exactly a major profit center. But you keep asking for tau shirts, so I keep selling them!
Thanks to all the tauists out there who continue to make this quirky project so much fun. Hope to see you at the party.
Happy Tau Day!
Michael Hartl
Founder, Tau Day
Author, The Tau Manifesto
Happy Tau Day, everyone! It’s hard to believe it’s already been six years since The Tau Manifesto launched and the real battle against pi’s supremacy began.
I don’t keep careful statistics, but I can confidently state that awareness of tau is enormously widespread. As an active member of the Caltech alumni community, for example, I frequently meet Caltech undergraduates, and they’ve virtually always heard of Tau Day.
Similarly, I’ve found in the programmer community that a fair fraction have heard of tau. In my own little corner of tech, every so often someone will freak out upon realizing that the author of the Ruby on Rails Tutorial and The Tau Manifesto are the same person. Indeed, today I hope to blow more than a few such minds, because I’ve just launched the new edition of the Ruby on Rails Tutorial book—on Tau Day!
One cool thing is seeing people wearing the Official Tau Shirt, which as usual is available for a limited time (sales expire tomorrow). For example, my mother reported seeing one on an elementary school student in Orange County, California, last year. And just a couple of weeks ago I was driving through downtown Los Angeles when I saw a woman wearing a Tau Shirt. I recognized her as my friend Carol Hoffstedt, so I rolled down the window and said, “Hey, Carol! You win!” I mean, what are the odds!?
As in previous years, people continue to amaze me with the incredible variety of creative projects inspired by tau. For example, an alert tauist passed along this remarkable Tau Day Sonnet, written for Tau Day last year:
As a big fan of the sonnet form myself, I can hardly imagine a better Tau Day present than this. Well, maybe beer (see below).
A second tauist, this one at MIT, told me about a “Tau Day Hack” involving “Tau on the Cow” (don’t ask me exactly what it means!):
I’m glad to see MIT picking up the tau ball and running with it—and challenge my fellow Techers at Caltech to do the same. (Hint, hint!)
Finally, the ever-enthusiastic Joseph Lindenberg passed along this fantastic bit of tau culture found in a most unexpected place: a specialty beer from Hawkshead Brewery called Key Lime Tau!
The [Key Lime Tau] beer, originally a collaboration brew with Crooked Stave (USA), is our take on a key lime pie. It was brewed on both sides of the Atlantic, hence two ‘pies’ and is 6.28% in strength.
6.28% in strength! How can you not love that?!
Alas, it looks like Key Lime Tau beer is pretty hard to come by, and I haven’t yet procured any for myself, but for next year I’ll do my best to fulfill the promise implicit in this lovely poster, and drink Hawkshead Key Lime Tau on International Tau Day!
Until next year—Happy Tau Day!
Michael Hartl
Founder, Tau Day
Author, The Tau Manifesto
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.