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# A Pi Day That Comes Once A Century: 3-14-15 At 9:26:53

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Just once per century, the date and time line up with the first 10 digits of the mathematical symbol pi (π). Saturday at 9:26:53 is the big moment.

Pi has perplexed and puzzled mathematicians for millennia. We learn it in school as having something to do with circles, but it turns up as the solution to lots of other problems, even when there are no circles involved.

Matt Parker is a mathematician at Queen Mary University in London. He's also a standup math comic and author of the book "Things to Make and Do in the Fourth Dimension."

"The thing that’s incredible about Pi," he told Here & Now's Robin Young. "Is it doesn't just limit itself to geometry. Everywhere you look in math, suddenly pi will leap out of the shadows."

For example, if you take all of the odd fractions: 1/3, 1/5, 1/7 and so on, "if you start with 1 and subtract and add the fractions, so 1 minus 1/3 plus 1/5 minus 1/7, if you carry on, the total you get is a quarter of pi. And if you add every single fraction together, 1, 1/2, 1/3 , all them, but you square them, you get pi squared divided by 6. So suddenly, everywhere you go in math, pi is there. And that’s why mathematicians get so obsessed with it."

### Guest

• Matt Parker, mathematician at Queen Mary University in London, stand-up math comic and author of the book "Things to Make and Do in the Fourth Dimension."

This segment aired on March 13, 2015.