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τ ☰
 * Home
 * The Tau Manifesto
 * State of the τ
 * A Parable
 * Forward to Victory!
 * A τ -stimonial
 * 10 5 Digits of τ
 * Languages
   * English
   * Español
   * Français
   * Italiano
   * Português
   * Deutsch
   * НА РУССКОМ ЯЗЫКЕ
   * 简体中文
 * Join τ Email List
 * Ebook / Tees





BUY PRINT EDITION

Buy the print edition of The Tau Manifesto at Amazon!





GET YOUR OWN TAU TEE

Celebrate Tau Day in style with a Tau tee shirt, available only for a limited
time from Teespring. Offered in both men’s sizes as well as fitted women’s.

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Read the State of the Tau 2024 update  |  Join the Tau Email List
Please enable JavaScript to render the math properly.
NO, REALLY, PI IS WRONG…
THE TAU MANIFESTO


BY MICHAEL HARTL

Tau Day is a celebration of the circle constant τ=C/r= 6.283185… Founded in 2010
with the publication of The Tau Manifesto by Michael Hartl, Tau Day takes place
annually on June 28 (6/28 in the American calendar system).

The Tau Manifesto’s introduction of τ (tau) as the “true circle constant” has
had a significant impact on geek culture, including changing the time of day MIT
announces its admissions decisions, being featured in the official Google
calculator, and being supported by a large number of computer programming
languages (including Microsoft .NET, Java, Rust, and Python).

Including the English-language original, The Tau Manifesto is currently
available in eight different languages. Its associated holiday, Tau Day, has
been featured in The Wall Street Journal and is celebrated annually on 6/28 by
thousands of math enthusiasts around the world.

To get all the latest updates on tau, read the State of the Tau update, and join
the official Tau Email List.


 * BUY PRINT EDITION
   
   Get the print edition of The Tau Manifesto at Amazon!


 * GET YOUR OWN TAU TEE
   
   Celebrate Tau Day in style with a Tau T-shirt from Teespring!


TAU VIDEOS

 * 
   Original Tau Talk (short version)
 * 
   Original Tau Talk (long version)
 * 
   The Tau Manifesto (animated version with sudgylacmoe)
 * 
   Pi Is (still) Wrong (Vi Hart)
 * 
   The Tau Manifesto (Talks at Google)
 * 
   What Tau Sounds Like (M. Blake)
   
   
   
   

ABOUT THE AUTHOR

Michael Hartl is a physicist and entrepreneur. He is the author of over a dozen
books, including Learn Enough Python to Be Dangerous and the Ruby on Rails
Tutorial, and was cofounder and principal author at Learn Enough (acquired
2022). Previously, Michael taught theoretical and computational physics at the
California Institute of Technology (Caltech), where he received a Lifetime
Achievement Award for Excellence in Teaching and served as Caltech’s editor for
The Feynman Lectures on Physics. He is a graduate of Harvard College, has a
Ph.D. in Physics from Caltech, and is an alumnus of the Y Combinator
entrepreneur program.

Michael is ashamed to admit that he knows π to 50 decimal places—approximately
48 more than Matt Groening. To atone for this, he has memorized 52 decimal
places of τ.

τ
 * τ Manifesto
 * State of the τ
 * 10 5 Digits of τ
 * A Parable
 * The τ Talks


 * BUY PRINT EDITION
   
   Get the print edition of The Tau Manifesto at Amazon!


 * GET YOUR OWN TAU TEE
   
   Celebrate Tau Day in style with a Tau T-shirt from Teespring!


 * SIGN UP FOR THE TAU EMAIL LIST »

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