一个多世纪以前，美国画家莫尔在法国接到了一封紧急家信，要他立即赶回美国去。这封急信已经在路上走了一个月，他迅速地买了一张返程的船票，而船却又要在海上航行一个月才能抵达美国，急得这位画家团团转。他立即奔回自己的舱房，记下了这么一段话：“电流可以突然接通，也 More than a century ago, American painter Molle received an urgent letter in France asking him to immediately return to the United States. The urgent letter was already on the road for a month. He promptly bought a return ferry ticket, but the ship sailed for another month at sea before arriving in the United States. He immediately rushed back to his cabin, noted the following passage: "The current can suddenly turn on, too