One of the first people to "prove" this theory--and it must be admitted that he only proved 160 of the billions of cases--was the psychologist Stanley Milgram. In the late 1960's, he asked 160 people in Omaha, Nebraska to mail a packet to a friend of his who lived in Boston. The catch was that they didn't have his address--they had to mail it to someone who they thought would get it closer to Boston. For each step, the idea was to get the letter one step closer, until someone could say "Oh, I know this guy!" and mail it to the rightful recipient. He found that somewhere around 90 percent of the letters that arrived did so in 5 or 6 steps.

One of the stranger facets of this experiment was that a majority of the letters he received came through just three acquaintances. Astonishingly, the idea of "six degrees" has become something of a paradigm (cough, cough): before the results were widely known, and before various publicity enhancing stories, plays, and urban legends, the people Milgram consulted for early estimates thought that it would take more than one hundred steps. Granted, that was before the Internet, but Milgram proved that on average, five connections will suffice, and six degrees is a near-certainty.

Other notable occurrences of the meme include