Have you seen Inception? In the movie, Dom Cobb uses a spinning top as a totem to tell dream from reality: it wobbles and falls in the real world but spins endlessly in a dream.

Surprisingly, this idea mirrors physics. At the heart of the debate between Einstein and Bohr is something just as strange as Cobb’s top: quantum spin—a subtle test of reality itself.

In the last episode (check here), we explored a simple game and showed that it is impossible to win more than 75% of the time. In this episode, we introduce quantum spin—a powerful new ingredient that allows us to play the game in a fundamentally different way—and use it to probe a much deeper question: What is the true nature of reality? And was Einstein or Bohr ultimately correct?