Every summer, scores of tourists take to the bustling streets of Barcelona, a city known for its breathtaking architecture. Nicolás Atanes Santos, a young Spanish mathematician, sees this as an ...

Once a century, a very special day comes along. That day is today — 9/16/25. Pi Day (3/14) often comes with sweet treats; Square Root Day (4/4/16 or 5/5/25, for example) has a certain numerical rhyme.