When asked to describe radio, Albert Einstein is said to have provided an eloquent description: "You see, wire telegraph is a kind of a very, very long cat. You pull his tail in New York and his head meows in Los Angeles. Do you understand this?" Einstein then continued: "Radio operates exactly the same way---you send signals here, they receive them there. The only difference is that there is no cat."
(Source: ARRL Letter- October 25, 1996)