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.

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With all due respect to Pythagoras, newly uncovered evidence suggests that his famous theorem, used to calculate the lengths of each side of a right triangle, might be 1,000 years older than him. That ...