The Twin Paradox
No you misheard. I said “twin PARADOX”. As in: a situation where the outcome seems counterintuitive or contradictory. The twin paradox is a famous paradox closely associated with Einstein’s Theory of Special Relativity.
Simply put, you take a set of twins. Born on the same day, on the same year, to the same Mom. We’ll call one of them Liz, and the other Ben. We take Ben and send him on a trip into space on a rocket (or throw him too close to a black hole)… and after a couple years, he returns from his exile and goes to see his twin. It’s their birthday after all (suppose that it’s also their birthday).
But as they put candles on their cake, they realize that Ben is MUCH YOUNGER than Liz! A whole handful of candles! How can this be? Neither twin has access to a TARDIS. Each twin denies undergoing any magical or science-y procedure (aside from the rocket trip, but Ben contends that he mostly just sat around in a room playing nintendo). Each twin recalls each and every day since they parted, years ago, and claims that nothing strange has happened. It’s a mystery! No! It’s more than a mystery: it’s a PARADOX.