Easy as pi

One day, at the beginning of a math class in high school, a classmate bet me that I couldn't memorize pi to 50 decimal places by the end of class. I did...and can still recite it to this day if anyone wants me to bore them to tears. I mention that only because of a nerdy Did-You-Know fact I had to prove at work today: If you use the value of pi to 40 digits to calculate the circumference of the observable universe, your answer will have a margin of error less than the diameter of a single hydrogen atom. I'll be damned, it's true. What a waste of those extra 10 digits I memorized.