# Half Tau Day is Fast Approaching! Hello all! I hope you're all gearing up for $\frac{\tau}{2} = \pi$ day! I am a giant proponent of $\tau$, and you should be too. For those of you who don't know, $\tau = 2\pi$. $\tau$ is a much more natural circle constant, as a circle is, after all, defined by its radius, not its diameter. One can find an incredibly compelling argument for $\tau$ in Michael Hartl's Tau Manifesto. I know I'll be spending Half Tau Day unwillingly participating in $\pi$ activities with my blissfully ignorant peers, who I will inevitably urge to join Brilliant and educate themselves about the marvels of $\tau$!

Have a safe and happy $\frac{\tau}{2}$ day! Note by Ryan Tamburrino
4 years, 11 months ago

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I feel stupid for asking this but isn't $\pi$ day on $14$ March?

- 4 years, 11 months ago

Yeah! This $\pi$ day is special though, because it will be (in the American format of month/day/year) $3/14/15$. $\tau$ will have its revenge on $6/28/31$!

- 4 years, 11 months ago

To be honest they are equally valid, as $\pi$ is better in some situations and $\tau$ is better in others. For example: circumference = $\tau$r may be easier to deal but then you end up with an area of: $\frac{\tau}{2}$$r^{2}$. You may also look at it from a trigonometry point of view... all the trigonometric functions repeat themselves every $\tau$ radians, but then when proving that $\zeta$(2) = $\frac{\pi^2}{6}$ you need $\pi$to obtain: $\frac{sin(x)}{x} = \displaystyle\prod_{n=1}^{\infty} (1-(\frac{n\pi }{x})^2)$ and the argument continues....

- 4 years, 11 months ago

I will concede a few small victories to $\pi$, including that one that you mentioned regarding the $\zeta$ function. However, if you look at the Tau Manifesto, Hartl shows that area of a circle with $\tau$ follows other quadratic forms of other formulas from physics. So, that $\frac{1}{2}$ out in front isn't quite as unnatural as it seems.

- 4 years, 11 months ago

Maybe there ought to be a friendly Tau vs pi debate

- 4 years, 11 months ago