How pi was almost 6.283185...

In some of his notes, Euler used π to represent 6.28... So why did we adopt 3.14...?
An equally valuable form of support is to simply share some of the videos.

The idea for this video, as well as the live shots, came from Ben Hambrecht, with the writing and animating done by Grant Sanderson.

Special thanks to:
- University Library Basel, for letting us rummage through their historical collection
- Martin Mattmüller from the Bernoulli-Euler center for helpful discussion
- Michael Hartl, author of the Tau Manifesto, for pointing us to obscure references
- Library of the Institut de France

Cinematographer: Eugen Heller

Music by Vincent Rubinetti:

Thanks to these viewers for their contributions to translations
Hebrew: Omer Tuchfeld
Korean: tebaioioo

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Various social media stuffs:

[jaredhouston]

The people who fight about tau and pi just go in circles

[johnchessant]

"It's often joked that formulas in math have to be named after the second person to prove them, because the first is always going to be Euler."
LOL!!!

[fakestory]

"have you ever heard of Euler's formula?''

" *which one?* "

[adrianmh]

"So which topic of maths did Euler influence?"
"Yes"

[CatherineKimport]

I still think we should define 🍕 = π/4 = τ/8.

🍕 can be defined as:
- the ratio of crust length to side length in an idealized pizza slice
- the ratio of pizza to box, given a perfectly circular pizza fit snugly inside a perfectly square box

[memestv]

Can you eat Pi? Yes.
Can you eat Tau? No.




Therefore we celebrate pi day.

[franzchandi]

tau should be for 3.14... and pi for 6.28... because of the # of legs

[johnchessant]

Pi Day is now both Einstein's birthday and Hawking's deathday. :(

[Knobbler]

Why is this even a thing? Just use tau when you want 2pi and use pi when you want tau/2

[qwadratix]

In Physics, pi almost never appears alone in formulae. It's 2 pi pretty much all the time.

[LoLrandmness]

Euler was one of the few actually concerned and engaged with math. My, to this date, favourite video of yours is the triangle of power, because it shows how to handle a problem, not the notation, while still hinting at how confusing bad notation can be.

[pcfilho]

Of all days, YouTube chooses to recommend me this on June 28th. I got your message, algorithm.

[arikwolf]

Pi is useful in Engineering because you measure pipes with calipers which gives the diameter.
Tau is useful in Mathematics because you draw circles with a compass which is set to the radius.
Eta* is useful in Electronics because the minimum and maximum absolute amplitude of a sine wave occur 1/4 way around a cycle.

* I think Pi/2 (Tau/4) is called Eta, but I am not sure.

[MorRobots]

3.14 has had a regular adoption due in part to the nature of practical engineering and manufacturing. I can accurately measure the diameter of a sphere or rod using a micrometer or calipers, I have to Infer the radius from that measurement. Additionally I have no practical way to find the center of a physical sphere or rod in such a way that I can take a direct measurement. I'm with grant on this one, it's not about what's right, it's about the problum at hand.

[TSPxEclipse]

I just realized that Euler probably used π=e at some point.

[johnchessant]

"...and writing a letter to the Bernoullis to boast about doing so afterwards!"
Hahahahaha

[NathanBudd]

I wish I had a circle of friends where on Pi day, they said "we should actually be celebrating 28th June"...

[KeithCooper-Albuquerque]

I often wondered where you stood on the PI vs TAU subject. Thanks for this interesting look at Euler!

[feynstein]

We should have an epic rap battle of history between Euler and Gauss.

[benjaminmeier]

Pi should be equal to 1/sqrt(3.141...), then it can be defined as the radius of the circle with area 1.