π pie by Robert Couse-Baker. Photo used under the CC-BY 2.0 licence.

‘Tis the season to celebrate the circle constant! ((Pedants would have me revise that to “a circle constant”.)) Yes, that’s right: in some calendar systems using some date notation, the day and month coincide with the first three digits of π, and mathematicians all over the world are celebrating with thematic baked goods and the wearing of irrational t-shirts.

And the internet’s maths cohort isn’t far behind. Here’s a round-up (geddit – round?!) of some of our favourites. In case you were wondering, we at The Aperiodical hadn’t forgotten about π day – we’re just saving ourselves for next year, when we’ll celebrate the magnificent “3.14.15”, which will for once be more accurate to the value of π than π approximation day on 22/7. (Admittedly, for the last few years, 3.14.14 and so on have strictly been closer to π than 22/7. But this will be the first time you can include the year and feel like you’re doing it right.)

Mathematical wordsmith Alex Bellos is consistently brilliant in his column for the Guardian’s Science section, and today he’s made not one but two posts: an article on constrained writing using the digits of π, and a collection of pictures of art which is based on the digits of π.

Internet maths superstar Vi Hart is here to explain why π isn’t all that (and in doing so, explains some other cool stuff):

[youtube url=http://youtu.be/5iUh_CSjaSw]

Evelyn Lamb, whom we love, has also written a blog post on her page at Scientific American about the prime number counting function, which uses the symbol π and makes a refreshing change from talking about the actual circle constant. Science magazine has a special π day page, which includes a list of their favourite pie recipes, while NASA has posted a collection of π-related puzzles.

Numberphile never misses a chance to get in on the action, and Aperiodifriend James Grime has a video about π and how it relates to the length of rivers, which is a lot more interesting than it sounds:

This isn’t the first video Numberphile has done about π: you can view their entire collection of π-related videos on their π playlist. Also today, they’ve created a piece of prog rock, which uses π in its construction, and turns out to be not half bad:

People around the world celebrate π day in their own way: restaurants worldwide are offering special menus, mostly involving pie, and in Chicago, the Illinois Science Council is organising a 3.14-mile walk (I strongly hope it’s around a circle of diameter one mile), starting at τ (6.28pm).

While you’re here, I feel compelled to remind you (in case you ironically hadn’t remembered) that our All Squared podcast last π day was about memorising digits of π, and comes in under 10π minutes long. Also from The Past, Simon Singh did a programme about π in his ‘Five Numbers’ series for BBC Radio 4.

Someone’s set up a “Pi Day official website“. It’s got some things about π on it, no doubt.

And finally:

Photo by Martha Soukup, used under the CC-BY 2.0 licence.