Einstein’s Thought Experiments, or, Cinema for the Mind
When he was in his early teens, Albert Einstein received a gift from a family friend: a series of illustrated science books with the catchy title of Naturwissenschaftliche Volksbucher ( People’s Books on Natural Science ), by Aaron Bernstein. In Einstein: His Life and Universe , Walter Isaacson quotes Einstein as having later described it as “a work which I read with breathless attention." In the first volume of Bernstein’s popular science series, he asked the reader to imagine a bullet shot through the window of a fast-moving train. Bernstein postulated that anyone examining the bullet’s exit on the opposite side of the train would conclude the bullet must have been shot at an angle. Bernstein’s point was that, because the earth is hurtling through space, light would exhibit the same refracting properties going through a telescope lens as the bullet passing through the train windows. And that this outcome would always be the same regardless how fast the source of the ligh...