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Mathematical Digest


Short Summaries of Articles about Mathematics
in the Popular Press

"Six Degrees of Speculation," by Karen Wright. Scientific American, June 2002, pages30-31.

Society can be thought of as a network, where two people are linked when theyknow each other. In the 1960s social psychologist Stanley Milgram did a studyto determine how many links it would take to connect certain people in Kansasand Nebraska with certain people in Massachusetts. Judith Kleinfeld, apsychologist at the University of Alaska in Fairbanks, recently read data fromthe study and disputes Milgram's conclusion that the average number of linksbetween people (that is, the average length of a chain like: person A knowssomeone who knows someone...who knows person B) is six. Other scholarsdiasagree with Kleinfeld and feel that Milgram's conclusion that it is a "smallworld" is valid. Indeed, mathematicians who have modeled large social networksagree that the average number of links between people is small. Duncan Watts, agraduate student of Steve Strogatz at Cornell, is conducting an email versionof Milgram's experiment. The article includes data from the game "Six Degreesof Kevin Bacon," in which actors are connected if they have been in a filmtogether: "The average Bacon number is 2.918 and no actor has been found to bemore than 10 degrees of separation from Bacon."

--- Mike Breen