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What is Pi Day and why is it today?


Why is everyone talking about 3.14?

Today is Pi Day, where mathematicians and pie-lovers come together to celebrate the elusive number and make terrible maths jokes.

Because the Americans write their dates in the month/day format, March 14 is written as 3/14, which are the first three figures of pi. Plus it’s Einstein’s birthday, which is nice.

Mathematicians are taking the opportunity to bake pies and generally celebrate the incredibly useful figure that is pi.

As silly as it sounds, the day was recognised by the American government’s House of Representatives in 2009, and it doesn’t get more official than that.

Now’s probably a good time to remind ourselves what pi actually is, and why it’s such a big deal.

Pi is a mathematical constant.

It’s really important in maths, because it’s the ratio of the circumference of a circle to its diameter (which is just over 3). Pi is a constant though, so is the same for any circle of any size.

But most excitingly, it’s irrational, meaning it can’t accurately be expressed as a fraction.

Its digits continue beyond 3.14 forever, without any repetition or patterns. Computers have managed to calculate it to more than 22 trillion digits beyond the decimal place, and people like memorising it, but such an accurate figure for pi isn’t needed for day-to-day maths.

Pretty cool right? Or is it just us?

Also it sounds a bit like the word pie, hence all the pies, so that’s cleared that up.

Piphilology, or memorising strings of pi decimal places for fun, is a serious business. The official record is held by Rajveer Meena, who recited 70,000 digits of the number in India in 2015.

The process took nearly 10 hours, while he sat blindfolded, reeling off digits for Guinness World Record officials.

Each to their own.

And obviously it wouldn’t be Pi Day without an actual pie.

Or cupcakes and cookies, which still count because they’re round, and you still have to use pi to make calculations about them.

Now this is the kind of maths we can get behind.

PA Media