[MUSIC PLAYING] TARA HOLM: Pi is an irrational number. You can't write it as a fraction. Pi is a transcendental number. That maybe sounds very highfalutin. We don't know whether pi is a normal number. Kids in elementary school know about the number pi. They know it's a number between 3 and 4, which is, I guess, what the Greeks knew, so that's pretty good.
We define this number mathematically to be the ratio of the circumference of a circle to the diameter of a circle. You need pi to calculate the trajectory of a rocket as it's taking off. You need pi to calculate the orbit of the Earth around the sun or the orbit of the moon around the Earth. As I'm riding my bicycle over to campus, the wheels are constantly traversing some number of pis.
We currently know about 23 trillion digits of pi. It's quite interesting, because that's more digits than a computer could possibly store. And so on some level, it's just a curiosity of our brains that we are obsessed with going further and further and further.
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Cornell mathematician Tara Holm explains the numerical value of pi and its applications.