## Pi Day Is Coming — But Tau Day Is Better 241

PerlJedi writes

*"A few months ago, a Tweet from Randal Schwartz pointed me to a YouTube video about 'Triangle Parties' made by Vi Hart. My nerdiness and my love of math made it my new favorite thing on YouTube. Now, with Pi Day coming up later this week, I thought it would be an appropriate time to point people to another of her YouTube videos: Pi is Wrong. The website she mentions at the end, Tauday, has a full explanation of the benefits of using Tau rather than Pi. Quoting: 'The Tau Manifesto is dedicated to one of the most important numbers in mathematics, perhaps the most important: the circle constant relating the circumference of a circle to its linear dimension. For millennia, the circle has been considered the most perfect of shapes, and the circle constant captures the geometry of the circle in a single number. Of course, the traditional choice for the circle constant is pi — but, as mathematician Bob Palais notes in his delightful article "Pi Is Wrong!", pi is wrong. It's time to set things right.'"*
## Agreed (Score:5, Funny)

## Re:Agreed (Score:5, Funny)

Being English, old-fashioned and inaccurate, I prefer to celebrate Pi Day on July 22nd.

## Re:Agreed (Score:5, Interesting)

## Re: (Score:2)

22/7 is misleading, in that people often think it's an exact value. I actually had math teachers in middle school who claimed as much, and refused to understand the term "transcendental number".

## Re:Agreed (Score:5, Interesting)

## Re: (Score:2)

tauday.com's manifesto is actually pretty compelling.

## Re: (Score:2)

## Re:Agreed (Score:5, Funny)

For now I don't really see the practical use of remembering Pi to that extent.

Chicks.

## Re: (Score:2)

And the next digit is zero. Memorised when I was 14 (25 years ago), I still remember quite a bit (and no, I don't recall it every day just to refresh my RAM).

I didn't use any method, just sheer determination (although I do remember it by sound more than anything, and I can't recall it in other languages without having to hum it to myself in my native language).

The brain is a strange thing... and I'm definitely not going to bother learning Tau by heart...

## Re: (Score:2)

## Re: (Score:3)

Because that's not the standard [wikipedia.org].

## Re: (Score:3)

Dude, you put the more significant digits first.

Pi is now 201203.14 (201.203,14 with European punctuation).

## Re: (Score:2)

Actually with European punctuation it is 14/3 - 2012 which is around 2008BC or something

## Re: (Score:2)

Pi is now 201203.14 (201.203,14 with European punctuation).

Depends upon which part of Europe you are from. In the English speaking part it would be 201,203.14

## Re: (Score:3)

“European punctuation” is an unfortunately generic term, if one includes the digit group separator in that definition, as you just did. While all of continental Europe (as well as the entire South America!) indeed uses comma as decimal separator, digit group separator varies. For example, Germans, Greeks, Italians and Swedes would group digits with dots, while Czechs, we Finns, as well as French and Poles would use spaces. (Thin) space is also used in some applications elsewhere in the world, du

## Re: (Score:2)

What, pi is 14.3? When did that happen?

It is a consequence of neutrinos going faster than light- all the laws of the universe are now backwards. And yes, Pie is now 14.3... or as an estimation 7 divided by 22.

## Re: (Score:3)

[whistling to self] hope no-one notices how I spelt pie... [/whistling to self]

## Cant eat a slice of Tau to celebrate. (Score:5, Insightful)

## Re: (Score:2)

## Re: (Score:2)

I'm trying to imagine Pi Carols...

Oh Pie Tree, Oh Pie Tree,How lovely is your crust baked...

Rudolf the red cherry piedeerWe three fillings, of orient are,figs, plums, kiwis stored in a jar

Timer Bells, Timer BellsTime to open the oven

## Re: (Score:3)

Wow, is your secretary some kind of frustrated geek or something?

I didn't even know there

werePi carols.## Re: (Score:2)

Hmmm maybe not Pi Carols but there are at least two Carol Pi's in the US according to Whitepages.com

## Re: (Score:2)

>Wow, is your secretary some kind of frustrated geek or something?Yes. Nice voice though.

>I didn't even know there were Pi carols.Google is your friend, or not. You may not want to know. For starters: try this. [teachpi.org]

## Re: (Score:3)

## Re:Cant eat a slice of Tau to celebrate. (Score:5, Insightful)

With Tau, you can have two pies.

## More for Particle Physicists (Score:3)

With Tau, you can have two pies.

Actually, if you are a particle physicist you can have a lot more - one tau can decay into 5 pis (although 3 is more common).

## Down with Pi !!! (Score:2)

I just watched the "tau" video and ... I actually agree with it. Making it the ratio of diameter/circumference instead of radius/circumference was a dumb move.

While we're at it can we swap the + and - on our electronic circuits?

## Re: (Score:2)

Bah, they're both boring. Let me know when it's Summer Glau Day.

## Re: (Score:3)

*According to wikipedia, this is the ONLY way to properly contemplate existence, unless, of course, my edit was edited.

## Re: (Score:2)

## Wait what? (Score:2)

## Re: (Score:2)

## Re: (Score:3)

Well with everyone so interested in the Mayans with thought; Oh, the Mayan calendar is 13 months long. We're gonna make ours 1 better you see? 14 is 1 better than 13. Our new calendar goes to 14!

## Triangle Panties (Score:2, Funny)

Darn.

I read that wrong.

I say we stick with pi. It's too labor-intensive to rewrite all the textbooks to read "tau" instead of "2*pi" and reteach everyone the new formulas.

## Re:Triangle Panties (Score:5, Insightful)

And, I think it's perhaps a little wrongheaded anyway. The area of a circle is pi*r^2. That'd become tau*r^2/2... You took the 2 out of one place and put it in another. And it does nothing for spheres: Volume = (4*pi*r^3)/3 = (2*tau*r^3)/3; Surface area = (4*pi*r^2) = (2*tau*r^2).

And besides, tau's already claimed as the "time constant" variable, so n'yah!

## Re: (Score:2)

The area of a circle is pi*r^2.

For most people, yes.

For some (including me), however, it will always be pi.d^2/4, for the simple reason that you can't easily measure an object's radius (measuring d then halving doesn't count). Seeing it that way might be ugly/wrong from a mathematical standpoint but practically speaking it seems more natural.

## Re: (Score:3)

(measuring d then halving doesn't count)

This is where I stopped reading your post.

## Re:Triangle Panties (Score:4, Insightful)

It is? Like what? There's a lot of greek symbols that are used for different things, so you have to look at what domain you're in before you make any assumptions about their values. This also applies to latin symbols.

Quick: what is

i? Well, that depends. If you're a mathematician, it's the square root of -1. However, if you're an electrical engineer, the answer is the AC current. In EE,jis the square root of -1. Omega, theta, tons of symbols like these are reused in different domains for different things.Offhand, I don't remember tau being used for anything else in mathematics (specifically geometry), so it seems as good a symbol as any. According to Wikipedia, there's a handful of mathematical uses for tau already, but they seem pretty esoteric (or obsolete, in the case of the golden ratio, which more commonly uses phi). It is used for a bunch of things in physics and biology, but those are different domains, so that's pretty irrelevant. You don't use pi (the circle constant) much in biology either, I imagine.

However, there are some greek letters that are barely used, so maybe one of those would be better. Upsilon, for instance, only has one use listed in Wikipedia's list of greek letters used in math, science, and engineering, to represent an elementary particle. Only physicists would ever see that (I don't think I ever saw that in college, as I was a EE major), so maybe that'd be a better choice than tau.

## Re: (Score:2)

## Re: (Score:2)

Sounds like the authors of this proposal weren't mechanical engineers. Maybe my upsilon idea would be better than their tau.

## Re: (Score:3)

i is always sqrt(-1). EEs just can't spell. Well known fact.

## Re: (Score:2)

Ok, sounds interesting, but I never heard of that in all my years of math (I was a EE major), and that's certainly something grade school kids learning basic geometry (or high school kids in trigonometry) aren't going to be exposed to. My point here is that just because a greek letter is used in some highly esoteric advanced field doesn't mean it should be forever reserved for that, when almost no one uses it for that or has even heard of it.

The other poster who commented that it'd create major conflicts i

## Re: (Score:2)

Yeah, sounds like a Tau of Babel to me

## Tau day is better (Score:5, Funny)

## Re: (Score:2)

But Einstein's birthday is best!

## FUCK Tau day (Score:2)

I'll never support those filthy Xeno bastards.

## Re: (Score:2)

## Re: (Score:2)

Surely she's capable of verifying that with a google search.

Convincing her it's anything other than a geek thing, well, that might be tougher. :-P

## Pi day will always remain the same for me (Score:2)

It's the day we're all comfortable with Sin(), further we're so accomodating we'll embrace Cos().

## Re: (Score:2)

tau day is better in this regard. It's easier to get a Tan() in June than march.

## Considering the counterpoints (Score:3, Interesting)

I do think tau is the 'better' constant, and both exploring the possibilities of what tau can do, and just 'playing around' with the math involved, has been enjoyable. However, to evaluate it properly and determine just how strong it is, a strong counterpoint is needed - and it is supplied in The Pi Manifesto [thepimanifesto.com].

Both its author and I recommend reading The Tau Manifesto (and Bob Palais's original work; both are linked in the article above) before reading The Pi Manifesto, to make proper sense of it.

In the end, I think tau is a much stronger choice than pi for some aspects of math; others, deserve further investigation. It may all be academic discussion, given how firmly pi is entrenched in our mathematics, but perhaps there's a solid place for both - with pi reserved for certain advanced concepts, and tau used through introductory geometry, trig and calculus.

## Re: (Score:2)

"Imagine we lived in a world where we used the lette

## Re:Considering the counterpoints (Score:4, Interesting)

The imperial system actually makes more sense for some things, depending on which measure you're talking about and what you're using it for. The whole 12 inches/foot thing can be easier to work with when you have to divide things evenly in quarters and thirds; by having something divisible by 12 instead of 10, you can easily divide by 3 or 4 without the math becoming complex. That's the whole reason 12 was the base for these units; back in medieval times, when they didn't have calculators and measurements were crude, it was easy to work with. Even now, woodworkers generally prefer English units for this reason.

Miles, however, don't make so much sense since they in fact are equal to 5280 feet. The big problem with conversion however, at least here in America, is that many things are based on miles. For instance, here in Phoenix, all the main streets are laid out along a 1-mile grid system. It's stupidly easy to see how far you'll travel from one point to another (using Manhattan lengths; except for Grand Ave, all the roads are N-S or E-W) just by looking at a map and counting the number of main roads in each direction. If we tried to convert to km, it'd be a mess. If I ask "How far is it from Baseline to Ray?" the answer is a simple "5 miles", just by counting the roads in between (Guadalupe, Elliot, Warner, Ray). In km, I'd count the roads and then multiply by 1.6, getting 6.4km, not exactly a convenient measure.

## Re: (Score:2)

Well, a mile is simply 8 furlongs, which was a more practical unit of measurement for land. For some reason a furlong (220 yards) is divisable by 11. I doubt that's an accident, but I've always wondered why it was important.

Historically a furlong is the distance that oxen could plow between rests, and so fields were generally a furlong in length along one axis. An acre is a furlong by a (surveyor's) chain, which made perfect sense at the time - and a chian is 1/10th of a furlong, so clearly Arabic numera

## Re: (Score:2)

5280 divides evenly by 2, 3, 4, 5, 6, 8, 10, 11, 12, 15, 16, 20... which makes it convenient when you want to parcel up land.

## Re: (Score:2)

Sorry, that should read "4 miles", not 5. It's 5 miles to Chandler Blvd, not Ray Rd, but I was trying to show an example where converting to kilometers yielded a non-integer result, and it turns out that 5 is one of the few cases where it converts to an integer value, so I changed to 4 but forgot to change that one numeral.

## Four thirds pi! (Score:5, Interesting)

Wait, what about four-thirds pi, the constant that relates the volume of a sphere to the radius???

Using 2pi as the so-called "constant" is two-dimensional chauvinism!

## Re: (Score:2)

4/3 pi r^3 is actually 2/3 or of a circumscribed cylinder or 2/3 tau r^3..

This tau thing kind of makes sense, though I tend to call it 2 pi.. If pie is good, two pi is twice as good.

## Re: (Score:2)

four-thirds pi = eight-thirds tau

just as complex in both cases.. neither case holds up as being singular for the sphere.

## Bah. e is better than them all (Score:3, Interesting)

## Re:Bah. e is better than them all (Score:5, Funny)

## Re: (Score:2)

we can say "2e or not 2e, that is the question."

Unless you use the Amerenglish pronunciation[*], you can say:

"2 pi or not 2 pi, that's the tau question".

[*]: At least they're mostly consistent, making "pi" rhyme with "bi-" and "Semper Fi". But not with "quay".

## Tau for the win (Score:4, Funny)

Tau is twice the constant Pi ever was!

## Re: (Score:3)

You could say it's two Pis and then sum.

## Pie are not squared! (Score:2, Funny)

## Re: (Score:3)

## tau is wrong (Score:2, Insightful)

## Re: (Score:3, Informative)

I know that some people will point out that e^(tau * i) = 1, which they'll claim is nicer than e^(pi * i) = -1

But the most beautiful equation in mathematics is e ^ (pi * i) + 1 = 0. The five most fundamental constants, being combined with the three most fundamental operators (addition, multiplication, exponentiation -- sorry, tetration), all equaling out, with absolutely nothing extra. There's no way to make it work as elegantly with tau.

## Re:tau is wrong (Score:5, Insightful)

Sure there is: e^(tau * i) + 0 = 1.

Hey, it's really not any more ridiculous than "... + 1 = 0".

## Re: (Score:3)

How in your mind is "x+1=0" ridiculous in the sense that "x+0=1" is? The former is a perfectly valid equation. Setting things equal to zero is extremely common, as anyone with even a middle school level education ought to know. Do you complain that x^2+2x+1=0 is a ridiculous equation too?

## Re: (Score:2)

That's like finding out all of Bob Ross' happy little trees were Photoshopped in during the commercial break. Tao is a "full-circle" representation, literally, while Pi is simply "half" assed. =)

## Re: (Score:3)

## Re:tau is wrong (Score:4, Informative)

No it isn't. It completely misses the point of e^(pi * i) = -1, which is that the left side gives you a bloody negative number.

The tau version is rather obvious, since you are squaring (-1). Put it another way, if e^(pi * i) had happened to equal 1, the tau version would be exactly the same. The tau version doesn't really tell you what is special about Euler's identity.

## Re:tau is wrong (Score:5, Insightful)

Umm, no!

e^(pi*i) = -1 implies e^(tau*i) = 1

e^(tau*i) = 1 does not imply e^(pi*i) = -1

The tau version follows from the pi version. The pi version does not necessarily follow from the tau version, because the tau version would still be true if e^(pi*i) = 1.

So the tau version is missing some very important information.

## "wrong" is a sensationalist word. (Score:3)

Seriously? People devote all this energy to replace a centuries-old constant by twice its value?

Isn't "wrong" a sensationalist word to use?

This is like many other things that are "wrong" - in the sense that there are technically better conventions to use, but the weight of history and inertia often keeps us from switching. Examples:

- Km vs. Mile. (SI units vs. Imperial..)

- Why are there 60 minutes per hour? Wouldn't it be better to have 100?

- Why do we use base 10 to express numbers? We should rather use base 8.

- Why 360 degrees? Why not 100 or 1000 (which is using base 8, of course, as mentioned above) instead.

## Re: (Score:2)

I'm in the minority I know- but I would be in favour of switching to a metric clock. Sure it would cause confusion at first. I'd be in favour of measuring degrees in fractions of 100 or 1000.

There again- I'm always in favour of confusion. It's always more fun than the status quo.

## Re: (Score:2)

haha, same here - actually in favor of switching for that case. That one was a bad example, then, I guess.

## Re: (Score:2, Interesting)

You complain about miles instead of km, but then you complain about using base 10? You're not even being consistent; if you favor base 8, then you should be against switching to kilometers or any SI unit for that matter, as their entire existence is based on the supposed superiority of base 10.

And why base 8? Why not base 12? 12 is evenly divisible by both 3 and 4, which is very useful in many real-world situations. 10 is only divisible by 2 and 5. 8 is only divisible by 2, so it really sucks to be hon

## Tau (Score:3, Interesting)

I'm not a mathematician, but that Tau "article" seems to steal a few bases.

It whines about A=(pi)r2 while C=(pi)D and how that shows that diameter is fundamental. But that's not the way I learned it anyway - the formula was always C=2(pi)r. Radius was fundamental, not diameter.

Which is even more obvious when you go into spheres, where everything is based off radius (A=4(pi)r2, V=4/3(pi)r3).

If we use diameter, you have to remember additional divisors (4 for the areas, 8 for the volumes). I can't speak on whether the whole "one turn" argument would help understanding other concepts, but aside from people who are working to become mathematicians, I suspect that the fact that the radius-based "magic formulas" are simpler will keep them around...

p.s. What magic brew do you have to use to get Slashdot to accept HTML codes like pi? Or Unicode? Every attempt ended up getting stripped, so I went with (pi).

## Re: (Score:2)

## Tau marathon bib (Score:3)

## Niether side is convincing (Score:5, Funny)

Both are irrational.

## Tau of Pooh (Score:2)

The problem with Tau is that it will always be associated with Pooh thanks to the book the "Tau of Pooh".

Pi day sounds way more appetizing than Pooh day. In the land of prunes, every day is a Pooh day.

## Oh and obligatory... (Score:3)

Oh and obligatory:

Taumorrow, Taumorrow, I love you, Taumorrow, you're only a day away......## It's nerd divided by zero (Score:2)

For sufficiently large values of nerd.

## Anyone going to bake a Pi-cake? (Score:2)

After a little research, I even found a recipe for pi-cake. Pi-Cake [instructables.com]

While an irrational pursuit, it looks to be a tasty one. Anyone thinking about making one?

## They're both wrong. (Score:2)

And yet, the circle needs a point to define the center, and an infinite number of points around the circumference to define the circle itself. The most perfect of shapes is a

point. It is the basis for all other shapes, both in flatworld, in 3d space, and in space-time. Without the point, there would be no point (pun intended) to trying to define a circle either as pi or tau (where is your center to get your diameter or radius from, hmmmm?).So,

## So if she weighs as much as a duck... (Score:2)

## Sigh (Score:3)

Pi will always be around because it relates to the diameter, which is easily measurable by actual humans in actual circumstances.

If there's a big circle on the floor, you can measure the diameter with a tape measure and one other person: stand on opposite sides of the circle, one end of the tape stays in one spot, and the other end gets moved back and forth until its length is as long as possible. The widest part of the circle == the diameter.

You can determine "the widest part of the circle" with simple physical measurements. Measuring the radius only requires a way to accurately determine where the center is, which is a non-trivial exercise. (Compared to the above.) Or you could measure the diameter and then divide by 2, but "measure the diameter" will always be one less step than "determine the radius."

## Re: (Score:2, Insightful)

No, it doesn't. Just using a different scale (x = 2y).

## Re: (Score:2)

Not even this. The angle is in radians. It won't change a bit.

Now, sin(pi*x) is not the same as sin(tau*x), but sin(x) doesn't care whether you prefer using pi or tau.

## Re: (Score:2)

What the fail? Using tau wouldn't change anything to the properties of cos and sin.

cos x and sin x are defined as the abscissa and ordinate of the point on the unit circle associated with an arc of length x. How does the name of a constant change anything to this definition?

## Re: (Score:2)

Because Pi is closer to 4 than it is to 3. If you're playing the Price is Right it is anyway.

## Re: (Score:2)

## Re: (Score:2)

The system I normally use is DDmmmYYYY, where mmm is a three-digit abbreviation of the month. I believe it's the standard for the US military. So today, for instance, is 12MAR2012. This system works well since there's no confusion about its meaning; since the middle three letters are obviously the month, and the last 4 obviously the year, the first two are obviously the day. Anyone in any country (at least who knows the English names of months, or can understand them well enough (most European languages

## Re: (Score:2)

So does the commonly-used (in Europe I believe) DDMMYYYY system; everything's sorted by day of the month without regard for month or year.

The problem with YYYYMMDD is that the year is first, and no one cares about that. When I look at the date on my computer or wherever, I already know what year it is, what I want to know is the current day. As a result, most date displays frequently omit the year altogether to save space. Then you don't know which is the month and which is the day (MMDD vs DDMM). With

## Re: (Score:2)

It sucks for sorting.

This is true, but I haven't yet discovered a good way of automatically sorting pieces of paper based on what I wrote on them :) When naming files, I always use the YYYY-MM-DD format, but when filling in forms for humans to read (especially non-technical ones of unknown nationality) I usually go with DD/MMM/YYYY.

## Re: (Score:2)

No, there should be 365.2422 degrees in a circle! That way, the Earth moves 1 degree per day!!!

## Re: (Score:2)

It's not that one is right or wrong, it's that one is easier than the other, and simplicity and elegance are always preferable to needless complexity.

For an extreme example, let's say that for some reason, people teaching math classes all suddenly decided to replace pi with a new constant, called Q, which is equal to pi * 13/59. Why? Just to make life difficult for everyone. So now, you're trying to teach little kids about simple geometry, and telling them that the circumference of a circle is 118/13 * Q

## Re: (Score:2, Informative)

But, my point is, it depends on the equation. Some might look simpler, some might not.

IMO, TFA is cherry picking. I'm sure there's a whole list of equations that would suddenly introduce new factors of 1/2 or 0.5, which most would consider more annoying than a 2.

For instance, the area of a circle would be (1/2)tau*r^2 - which seems a bit awkward to me. Since tau = C/r, You could simplify it to (C*r)/2, but again - fractions are awkward to write, especially with a keyboard, and mistakes get easy to make.