“What is any of this good for and when would we ever use it?”

“Pi. The ratio of the circumference of a circle to its diameter. And this is just the beginning. It keeps on going, forever, without ever repeating. Which means that contained within this string of decimals is every single other number. Your birth date, combination to your locker, your social security number. It’s all in there somewhere. And if you convert these decimals into letters, you would have every word that ever existed in every possible combination. The first syllable you spoke as a baby, the name of your latest crush, your entire life story from beginning to end. Everything we ever say or do… All of the world’s infinite possibilities rest within this one simple circle. Now what you do with that information…what it’s good for…well, that would be up to you.”

——Person of Interest S2E11