Thought experiments are your very own reality-distortion field, your choose-your-own-adventure game—your purple crayon. The purple crayon was Einstein’s favorite scientific tool, one that he carried with him even as an adult.18 As he wrote to a friend, “You and I never cease to stand like curious children before the great mystery into which we were born.”19 Centuries earlier, Isaac Newton purportedly used similar words in describing himself as “a boy playing on the seashore… whilst the great ocean of truth lay all undiscovered before me.”
