The Unapologetic Mathematician

Mathematics for the interested outsider

That Greek constant

I evidently can’t say “\pi” in the title to a post. Today I’ve seen a lot of people talking about “\pi Day”, though, so I suppose I’m expected to do so as well. So I will.

I hate \pi day. Hate hate hate hate hate this day. Hate it. Hate every simpering stupid vacant mathematics-insulting moment of it. Hate the sensibility that thinks anyone will like it. Hate the implied insult to mathematics by its belief that anyone would be entertained by it.1

Let me put it this way: why don’t we have a “The Sky Is Blue Day”? It’s about as obvious. The constant \pi shows up everywhere for very good reasons, and once you’re really comfortable with it you’re just not that impressed. There has to be some constant satisfying any one of its definitions, and those all have to be the same thing. Beyond that, the decimal expansion — 3.1415926535… — is purely an accident of our notation for real numbers. When I see the same taped-glasses pedants who whine that the year 2000 is only an accident of base ten turn around and join in this silly fetishization of \pi it’s incredibly depressing.

And then there’s the argument that this sort of thing acts as a springboard for mathematical interest. Listen carefully here: the only people who care about \pi Day are already interested in at least applications of mathematics. That \pi has such-and-so a value isn’t going to win any converts, and recitations of its decimal expansion make nonmathematicians think we’re all some sort of social outcasts who have nothing better to do with our time than that — if that’s what mathematics is, why bother going into such a dry and boring subject? Besides which, Lore Sjöberg said it best: “A value of pi that’s accurate to the 31st digit is good enough to measure the circumference of the entire universe within one proton, so anything beyond that is bordering on the mathsturbatory.”

Anyway, \pi works the way it does for all sorts of good reasons, and it’s very well understood why. There are other constants with just as complicated expansions that we have very little idea why they work the way they do. Why not come up with a day for Feigenbaum’s constant?

So, mathematicians throw off the shackles of \pi Day.

1 With apologies to Roger Ebert

March 15, 2007 - Posted by | rants


  1. pssh. grinch.

    Comment by anon | March 15, 2007 | Reply

  2. Then you must love 1K day. That’s October 24, as in 1024. It’s a computer science thing, and every bit as bad as pi day.

    Comment by ChuckO | March 15, 2007 | Reply

  3. As some small consolation, yesterday was also Steak and a B-J day.

    A much more entertaining set of things than pi. Or Pie, even.

    EDIT: bowdlerized the comment slightly. I like to skirt the bounds of good taste, but words are one of those things some people freak out and won’t let their kids become mathematicians over — UM

    Comment by efm | March 15, 2007 | Reply

  4. Hello.
    Don’t normally write comments but i disagreed with you so i though i might as well.
    I agree that the notion of “pi-day” is complete crap, especially since i only works in the American Month/Day/year system. It makes no sense to have the smallest period (day) in the middle???
    Anyway… the part that I don’t agree with is the part about not being impressed by constants such as pi. This sounds very foreign to me. I am supremely impressed by the intricate and often beautiful properties of mathematical constants such as pi.
    As to the “accidental” value of pi, you are right that the value is of course only one which is based on our numerical notation, but constants such as pi still have some more fundamental identities than simply their decimal expansion… this is what is often the wonderful thing about them
    thank you

    Comment by Martin Speirs | March 16, 2007 | Reply

  5. Martin, you’re right that there are other properties than the decimal expansion, but as hard as I look I’m hard-pressed to find more than one fundamental such property: pi is the injectivity radius of the unique compact, one-dimensional Lie group.

    Of course there are other starting points. I’m sure Serge Lang would have said something about the heat kernel. But whatever place you start from, everything else about it follows from that one fact. What’s so amazing isn’t that pi does all this, but that the structure of mathematics itself links all these things together.

    Mathematics points towards beauty. Pi Day tells us to look at the finger.

    Comment by John Armstrong | March 16, 2007 | Reply

  6. Like Mole Day in Chemistry, π day is essentially a joke. Yes, it is a misuse of a decimal expansion, that’s what makes it amusing.

    Comment by Michael Micek | March 15, 2008 | Reply

  7. I know it’s a joke. I just don’t think it’s funny, and it perpetuates a negative and harmful stereotype. How about we start celebrating Al Jolson day by wearing blackface?

    Comment by John Armstrong | March 15, 2008 | Reply

  8. The quote by Sjöberg reminds me of the comic entitled How many digits of π do you know?

    Comment by Mark Reid | March 15, 2008 | Reply

  9. Excellent! Do you have any rant on multiplication table competitions?

    Comment by Val | March 16, 2008 | Reply

  10. I don’t see any reason to get snobbish, by your reasoning I can’t poke fun of someone born on the leap day of February because it is a random calendar event. And that’s no fun.

    The biggest problem I have with these days is that Americans are backwards, it is 14 March for god’s sake, and it is so EVERYWHERE in the world with the exception of the nation that brought you manifest destiny, the cheeseburger and marched in after the war was won and still won’t shut up about it drawing close to a century later.

    Comment by Bob^3 | March 17, 2008 | Reply

  11. […] of others that do too. And one of the very few undeniably mathy words that almost everyone knows is that blasted Greek constant , so it gets called into service a […]

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  14. It’s for exactly one thing: making circular desserts that stretch the definition of ‘pie’ and feeding them to your friends. By the cruel rigors of scheduling, I always have an exam the next day, so pi day is also for pretending to study while enjoying a slice of pastry.

    Comment by tensory | March 14, 2013 | Reply

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