A pair of pi enthusiasts have calculated the largest chunk of the mathematical constant yet, reaching just over 10 trillion digits. Alexander Yee and Shigeru Kondo, respectively a computer scientist in the US and a systems engineer in Japan, fought hard-drive failures and narrowly missed widespread technical disruptions due to the Japan earthquake to break their previous Guinness world record of 5 trillion digits.

As the title of the announcement on their website - "Same program, same computer, just a longer wait..." - suggests, it was only a matter of time before the record was smashed. Indeed, calculating so many digits of pi serves no useful mathematical purposes - pi goes on forever, but just 39 digits are enough to calculate the circumference of a circle the size of the observable universe with an error no larger than the radius of a hydrogen atom.

Yet, as demonstrated by Yee and Kondo's recent epic quest - which was particularly fraught this time around - the feat still sparks intense passion, a testament to the enduring fascination with this curious ratio.

Yee wrote the pi-calculating software while Kondo performed the number-crunching on his custom-built PC, adding another ten hard drives since the previous attempt to calculate pi.

Calculations began on 16 October last year and were over a third complete when a hard drive failure on 9 December meant the pair had to start from scratch - the failure occurred just before a scheduled backup. Then the earthquake struck on 11 March, soon after the pair had reached 47 per cent completion.

Thankfully, Kondo was fine and the earthquake failed to disrupt the pair's calculations, as his PC was connected to Japan's unaffected western electricity grid.

Further hard-drive failures, and subsequent replacements, however, slowed things further until finally, on 26 August, the feat was complete. The calculations required were so intense that Kondo's computer heated the air in its room to nearly 40 °C. "We could dry the laundry immediately, but we had to pay 30,000 yen [$400] a month for electricity," his wife Yukkio told *The Japan Times*.

The pair then had to verify that all 10 trillion digits were correct. After all, no one had ever calculated them before. Thankfully there is a formula for calculating any particular digit of pi, which they could use to check the result. A researcher at Yahoo used the same formula last year to find the 2-quadrillionth binary digit of pi.

One final step remained: converting the digits from base 16, the number system used to carry out the calculations, to base 10, the familiar system we use ever day. The pair finally finished this step last Sunday. Phew.

Oh, and in case you are wondering, the 10 trillionth digit is 5.

* Top image: Pi-crunching machine/Alexander J. Yee & Shigeru Kondo. This post originally appeared on **New Scientist**.*

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