It started life as the number of times you can fit a circle’s diameter round its circumference, but it appears throughout mathematics. It’s not a simple number: mathematicians describe it as “irrational and transcendental”. In September 2010, the well-named Nicholas Size, of Yahoo, computed its value in binary to 2 × 1015 digits – you don’t often need that many . . .
It’s a very strange number, is pi:
It’s ‘transcendental’ – though heaven knows why.
3.1416 is the usual mix;
More precision’s just π in the sky.