The pi is a lie… Happy Half Tau Day!

http://halftauday.com/?

by mhartl • 15 years ago

196 108 15 years ago

halftauday.com

GavinB• 15 years ago

If we don't fix this, everyone at the galactic congress is going to laugh at us.

younata• 15 years ago

I will start using tau exclusively the minute I don't get F's in math for using it.

joshkaufman• 15 years ago

That's why it's a "pedagogical disaster."

rudiger2• 15 years ago

How are you getting Fs for using τ?

Just write `Let τ = 2π.` at the top of your papers.

pnathan• 15 years ago

But if we don't use Pi, then how can the international brotherhood of Eta Beta Pi exist (hint, say it fast)?

archangel_one• 15 years ago

If the only thing the others at the galactic congress laugh at us about is our usage of pi instead of tau, I reckon we'd be doing pretty well :)

zyfo• 15 years ago

They'll also laught at the west for seeing chess as the ultimate intellectual game instead of Go.

While the Baroque rules of Chess could only have been created by humans, the rules of Go are so elegant, organic, and rigorously logical that if intelligent life forms exist elsewhere in the universe, they almost certainly play Go. - Edward Lasker

snissn• 15 years ago

This joke is starting to get pretty annoying..

There are lots of things we do for conventional reasons, such as having electrons exhibit negative charge.

If you're doing any actual complicated math or physics, the last thing you care about is having a different constant floating around in your terms.

What it is, however, is a great learning tool - This thing called pi, maybe we could get away with, or even be better off calling it 2pi. - Can get lots of people thinking about math and possibly learn something cool like trig. But when used in a psuedo intellectual way, it 'really grinds my gears'.

anonymoushn• 15 years ago

Electrons exhibiting negative charge is something that would be difficult to fix because the fix would result in a lot of confusion. Using tau as the circle constant doesn't cause nearly as many problems. I don't see it as a joke; we should do it.

amalcon8• 15 years ago

It strikes me as more analogous to using j = sqrt(-1) so that it doesn't conflict with current: it works fine, but you're never going to get everyone to do it because people want the papers to stay consistent.

Actually, in this case, there's a particular discipline that's especially inconvenienced (physicists, due to the torque conflict). Contrast with j: there's a particular discipline that benefits, and they use j=sqrt(-1) all the time.

rudiger2• 15 years ago

Perhaps you're right about people doing "actual" complicated maths simply not caring about a multiplicative constant. However, a lot of people do most or all of the complicated maths they're ever going to do in their lives when they're in university. During this period, the correct symbol makes every formula and equation simpler and easier to learn. Crucially, it's also during this period that people's understanding of complicated maths is most important, as they are judged by letter grades upon which many of life's opportunities depend.

amalcon8• 15 years ago

How often do people actually make this error? I make all sorts of errors of that class when doing math by hand, but I've never once been off by a factor of two because the formula calls for 2pi.

gte910h• 15 years ago

I'm not so sure it is a joke. The author clearly states it's more for neophytes. And the convention can be explained of using 2π after showing what it all means by explaining Tau

If nothing else, we should at least get a non-separated printing character that looks like 2π connected up, similar to latin dipthongs.

tybris5• 15 years ago

No need to look so far. The area of a circle is πr^2. π without 2 is used everywhere.

natep3• 15 years ago

But in analogous equations (energy of motion .5mv^2, energy of spring, .5kx^2), there is a 1/2. Basically, anytime you integrate a linear equation, you get a factor of 1/2. Using pi as the circle constant hides this fact.

http://tauday.com/#sec:circular_area

natep3• 15 years ago

If you're doing complicated math or physics, the last thing you want is to be off by a multiple of 2 when you're done. It's happened to me enough times, I almost wish I were still doing physics so I could use tau instead of pi.

For electron charge, I have, at times for intermediate calculations, used 'e' in place of the negative sign from electrons, and then substituted -1 at the end. Being off by a multiple of -1 is just as annoying as a multiple of 2.

billswift3• 15 years ago

Even more annoying since it is even easier. Losing a negative sign is the most common mistake I make working through a complicated problem. Your idea of using something less likely to be overlooked when transcribing intermediate steps in solving a problem strikes me as a really good idea. Thanks.

amalcon8• 15 years ago

Not to mention that they seem to have chosen one of the worst possible symbols: the one that happens to represent torque. Further, it looks a lot like t, which is often used to represent turns (== cycles == 2pi radians).

There are alphabets out there other than the Latin and Greek ones, with plenty of untapped symbols.

loup-vaillant3• 15 years ago

> it looks a lot like t, which is often used to represent turns

I see that as an asset. It makes the correspondence between 2Pi and one cycle even more obvious.

maxbRuns• 15 years ago

I don't see it as a joke. Why not strive for the conceptually cleanest possible conventions?

It's pretty plain to me that tau is more deserving of the status of 'conceptual entity' than pi is. It's the number of radians in a cycle. Practically every time it occurs in physics, pi represents 'half the number of radians in a cycle'. Kind of crufty if you ask me.

abecedarius• 15 years ago

When you're programming something complicated, arbitrary ugliness in the APIs you're using brings you more trouble than when you're programming something simple. Right? So what's different about complicated math or physics?

That's how I realized pi was wrong, back before the manifesto came out -- from looking at math the same way I'd learned to look at programs.

techiferous2• 15 years ago

This is not a joke any more than the dvorak keyboard layout is a joke or the metric system is a joke. It's an objectively better approach whose only drawback is the overwhelming force of tradition.

ek• 15 years ago

You cannot compare use of the metric system to use of Dvorak or tau=2pi. While Dvorak and tau may be objectively better, the real world gains to be had by switching to either are slim in reality. I already type upwards of 90 words a minute on Qwerty and I doubt that switching to Dvorak would yield much of a gain to my typing. The problem behind pi is that it is never explained correctly, and this can be worked around by fixing pedagogy without having to introduce yet another physical constant. If the United States switched to the metric system, however, doing business with foreign economies would immediately become easier and we would no longer have to memorize long tables of arbitrary conversion factors. It makes much more sense objectively AND pragmatically to use units that are derived from physical quantities, rather than legends about kings' feet and so forth. With the other two examples, the pragmatic improvement isn't there -- the improvements in quality of life/quality of thought that we would experience simply aren't worth the trouble of switching.

itsnotvalid• 15 years ago

Just missing a stroke under the horizontal line.

Fice2• 15 years ago

Just think of 2π as a single symbol — the circle constant. Why do we need another name for 2π?

tspiteri2• 15 years ago

Is 22π equal to 2 times 2π or is it equal to 11 times 2π? That is, is 22π equal to 2(2π) or (22)π? If 2π is a single symbol, then 22π would be equal to 2(2π), which would be really confusing.

Fice2• 15 years ago

What I was trying to say is that there is no need to introduce another symbol τ as we can simply refer to "the circle constant" as 2π. I am not suggesting to treat 2π as a single symbol in formulas.

ilovecomputers2• 15 years ago

I'm sorry, but on pi day, I eat a whole pie. I am not settling for half a pie.

camiller3• 15 years ago

No no, tau is 2pi. So eat 2 pies.

kissickas• 15 years ago

On June 28th. Today you can eat half a tau...

wallflower• 15 years ago

Good luck to those who hope and dream to attend MIT, for today is admissions decision day! 3/14 9:26pm (not 1:59pm this year because of Class of '15)

cjtenny• 15 years ago

I sent this link to the admissions staff. 6/28 decisions next year, perhaps?

nickbarnwell• 15 years ago

I think that might be a bit cruel to those who get deferred in December, not to mention slightly impractical ;)

Only 7 hours and 15 minutes to go....

dskhatri2• 15 years ago

MITLeaks: http://www.mitadmissions.org/topics/apply/the_selection_proc...

graywh3• 15 years ago

It's funny when the dup makes the front page and the original doesn't. Guess it's all a matter of timing.

http://news.ycombinator.com/item?id=2322355

mhartl2• 15 years ago

I saw the first submission, but I wanted to use a different headline, so I appended a question mark to the URL and submitted a new link. It's always a good sign when people submit your stuff before you do, but in this case I had a clear idea of what I wanted the headline to be. If I recall correctly, essentially the same thing happened on Tau Day itself, with the same result.

graywh3• 15 years ago

And I didn't realize you were the duper until later.

billswift3• 15 years ago

Actually, when I first saw them, they each had 4 upvotes and were side by side on the front page.

tybris5• 15 years ago

bah e^(0.5τi)+1=0

tspiteri2• 15 years ago

> bah e^(0.5τi)+1=0

nah e^(τi)=1

tybris5• 15 years ago

Well darn, that looks even nicer.

pixcavator2• 15 years ago

It's not as good! You can get it from the original formula easily, but not vice versa.

Dabacon• 15 years ago

e^(τi)-1=0. This is obviously better since it not only contains the fundamental constants e, tau, and the beautiful numbers 0 and 1, it also includes a minus sign, emphasizing the fact that we are working over a field with an additive inverse. ;)

snes• 15 years ago

e^(iT)=1

http://vihart.com/blog/pi-is-still-wrong/

sp332• 15 years ago

This tau video was posted already, but it's off the front page and... you really need to see it! http://news.ycombinator.com/item?id=2321796

mhartl2• 15 years ago

I love this video. Vi Hart says, "No! You're making excuses for pi." With this beautifully succinct exclamation, Vi cuts through the pi smokescreen and puts her finger squarely on the problem. This phrase will, I think, become a rallying cry for tauists everywhere. As the author of The Tau Manifesto, I am proud to have Vi on Team Tau!

lmkg• 15 years ago

Tau is only convenient in geometry. In calculus, Pi rules the day because the natural unit is radians. Since I like calculus more than geometry, I won't be accepting Tau anytime soon.

loup-vaillant3• 15 years ago

Then why the full angle is 2 dammed Pi radians? I prefer the simpler Tau radians instead.

dougws• 15 years ago

Read the Tau Manifesto (linked int he article). He covers that and shows why Tau is easier to use there, too. Dude was a physics prof at Caltech; I think calculus is sort of important to him, too.

ddlatham• 15 years ago

If your natural unit is radians, then you're arguing for tau rather than against it.

How many radians in the circle? Tau

How many in half a circle? Tau / 2

How many in a quarter turn? Tau / 4

Much better than mentally switching from a quarter circle to half a pi.

And if you're using it in calculus, it's more natural to integrate from 0 to Tau than from 0 to 2 Pi.

sophacles3• 15 years ago

Wait..

1. Calculus was invented to make the geometry easier -- basically opposing geometry and calculus is a broken idea.

2. Geometers use radians too.

3. All the stuff other repliers said about 1 tau radians...

dskhatri2• 15 years ago

Tell that to my 12-year old nephew who memorized π to 128 decimal places in celebration of today! He'll be heart-broken to find out he memorized an inconsequential number.

waterhouse3• 15 years ago

I memorized π to about 180 decimal places at age 9, but I supported the switch to τ when I read about it, and I have no regrets.

jonsen• 15 years ago

He should have memorized π in binary then.

graywh3• 15 years ago

only the last bit is different (if you can find it)

3pt14159• 15 years ago

I'm having a bit of crisis. Ever since I found out about Tau, I just can't look at my username the same. Maybe I can get it changed to 6pt283185?

In either case: Happy me day!

camiller3• 15 years ago

Hmmmm....

You are half the man you should be.

;)

tokol• 15 years ago

I already bought a pie for the office. Where can I find a half Tau?

bugsy• 15 years ago

This whole thing is ridiculous because it ruins the whole justification for baking pies on 3/14.

Those of you that want to study the Dao De Jing on 6/28 are free to do so but please leave those of use that eat pies on 3/14 alone.

rtaycher• 15 years ago

At my HS they gave everyone a piece of pie on pi day.

randomibis• 15 years ago

Every objection here is answered succinctly and powerfully at http://tauday.org/

I suggest you read it if you haven't done so.

justatdotin• 15 years ago

that's 14.3, not 3.14

gsivil• 15 years ago

Maybe we should wait for June the 28th for that discussion. Just to show some respect for pi that was with for quite some time

VladRussian• 15 years ago

well, Gamma(1/2) = sqrt(pi), putting tau there wouldn't make things better.

redcap• 15 years ago

While we're at it, can we please:

- change electric theory so that it's a flow of negative charge and not positive. - get the US to use SI units instead of Imperial or whatever they think they're using.

sliverstorm2• 15 years ago

I dunno, I'm rather fond of people forcing pie into my hands on Pi Day...

DennisP2• 15 years ago

Kinda messes up Euler's Identity.

http://en.wikipedia.org/wiki/Euler%27s_identity

DennisP2• 15 years ago

Ok, so I read down further and I'm wrong.

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The pi is a lie… Happy Half Tau Day!

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