As I said this time last year, and will probably continue to say every year I’m still blogging: “Happy Pi Day”.
This is nothing to do with pies of the edible variety or with the Raspberry Pi, although both will probably be featuring in my celebrations. Rather, it is a celebration of the mathematical constant, π (or “pi”, for those of you who don’t read Greek or maths), which is the ratio of a circle’s diameter to its circumference. This is a universal constant for all circles (at least in this universe!) and its value, despite attempts (apparently) by at least one US state to legislate a change to 4, is approximately 3.14159. That’s as many digits as I can generally remember without having to look it up, and is sufficiently accurate for most purposes (actually, 3.14 is good enough quite often). Since π is irrational, its exact value cannot be written as a ratio of integers (aka. a fraction) or a finite decimal.
In case you’re wondering why π is celebrated today, it helps to look at the date in either ISO or US standard format. In the UK, we’d usually write today’s date in figures as “14/3/2013” – that’s the 14th day of the 3rd month in the year 2013AD (or CE if you prefer). The US version would be “3/14/2013” and the ISO version “2013-03-14”. Leaving aside the question of which order is most logical (FWIW, IMHO it’s ISO, closely followed by UK, with US a long way behind), if you drop the year then both the US and ISO versions leave you with “3.14” (using a cunningly chosen neutral separator for the two remaining parts of the date), which should make it obvious why Pi Day is today. If you’re wondering why we bother to celebrate Pi Day at all, you’re probably not a mathematician. 🙂
As alluded to earlier, I make full use of the homophony between “pi” and “pie” as an excuse to celebrate Pi Day with the eating of pies. I haven’t yet been to the shops today, so I don’t know what sort of pie I’ll be eating, but it will probably be a pork pie for dinner followed by a rhubarb pie or treacle tart, or something like that, for pudding. Sadly, I won’t have time to bake my own pies this year, so I’ll have to rely on commercial offerings. I’m not sure how non-English speakers celebrate Pi Day without conveniently homophonic comestibles in their languages.
As well as eating pie, I usually celebrate pi day by listening to songs about pi (of which I only know one — Pi by Kate Bush) and songs about pie (of which there are many). I have set up a Spotify playlist of about 40 songs mentioning pie in the title, which I’ve listened to on Pi Day for the last several years. This year, by way of change, I decided to just listen to songs from my own music collection with pie (or pi) in the title. There are rather fewer of these (just 8 currently on my computer), including Don McLean’s American Pie, Bob Dylan’s Country Pie, 3 versions of Charles Mingus’ jazz classic Goodbye Pork Pie Hat (one by Mingus himself, one by Swedish sax/flute player Magnus Lindgren and a rather tasty guitar version by John Renbourn), and a cover by my own band, the Rice Hooligan Orchestra, of June Christy’s Shoo Fly Pie, as well as the aforementioned Kate Bush song, which mostly seems to be a recitation of the first few hundred digits of π set to music.
Since last year, of course, I have acquired a Raspberry Pi, so if I get time later today I’ll probably do a bit of tinkering with that as part of my celebrations. My Pi has been slightly neglected of late, as I’ve been concentrating on other things. Since my last post on the subject, I’ve picked up a LedBorg, a fairly simple expansion board for the Pi which essentially adds a multicoloured LED operated via the GPIO interface. I have got this up and running and written a couple of simple scripts for it but my next plan is to rewrite my tea timer script to use the LedBorg instead of a lashup of LEDs and resistors on a breadboard).
Incidentally, I gather that an authentic Greek pronunciation of π would be “pee” rather than “pie” but for the sake of celebrating in homophonic style I’m more than happy to go with the anglicised mispronunciation. 🙂