"Only two things are infinite, the universe and the human stupidity..." - that's how a popular quote by Albert Einstein starts. He forgot about one other infinite thing: pi, which is as important as the universe and as irrational as human stupidity. Fun fact: Einstein was born on March 14, which is celebrated as world pi day, since in the American system that date is written as 3/14. This episode of The Intersection takes a look into the many different aspects of pi and explains why this number is so important.

We think we know pi, but we understand just the basics. Yes, it's the ratio of a circle's circumference to its diameter. Yes, it's crucial in determining a circle's area, a sphere's volume, and, by association, in trigonometry calculations. That's pretty much the entirety of what school mathematics teaches us about pi. But, there's a lot more to it.

For example, here's a fact that's probably going to surprise a few: the fraction 22/7 is actually an *approximation* of pi. Pi fascinates academics and non-academics alike. Krishan Chahal fell in love with pi while he was looking for non-repeating numbers that he could memorise. The ex-world record holder in memorising pi's digits (he's currently third on the list), tells Samanth & Padma about the one aspect of pi that has foxed and enticed mathematicians for ages - the decimal numbers of pi follow no discernible patterns.

Yet, from the Babylonians in 1900-1600 BC and the Egyptians around the same time to ancient Indians in 700 BC and the Chinese in 100 AD, our ancestors had various approximations of pi. Why have we been so obsessed with pi? It's probably because pi crops just about everywhere - from the helixes in our DNA to the larger cosmos. In fact, pi can also be found in a river's shape - the ratio of a river's actual length to that of the hypothetical straight line from its source to its mouth averages pi.

So the next logical question is, did we invent pi or does it actually exist in nature? The question, both Samanth and mathematician Arvind Iyer believe, is almost philosophical in nature. For Arvind, it boils down to personal belief. "Whatever I do, I am in the process of discovering than inventing," he tells Samanth & Padma.

Yet another aspect to pi is the debate in the mathematical world on replacing pi with another mathematical constant, tau (which is two times pi), since it occurs more frequently in nature than pi. This is a valid point, but as Arvind explains, pi is so ingrained in mathematical culture that replacing it would be just creating chaos.

The cultural connect can also explain our fascination with this number. Arvind believes that for most of us, pi is the first trivial thing that we come across in mathematics. "Why this number? Why not two? What's so special?" This might just be yet another effect of pi - stimulating our curiosity and acting as a pathway into mathematics, as we look to find out more about the mysteries of this number.

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