Einstein Science Reporting for Kids
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It's a small world after all

An email message you send could reach almost any computer in the world, after being forwarded about six times.
Click here for a high resolution photograph.

An email message sent from one computer could reach almost any other computer in the world, after being forwarded about six times, according to a new study in the August 8 2003 issue of the journal Science. Back in the 1960s, researchers did a famous experiment where they learned that most people are connected to each other through a chain of about six acquaintances.

Map showing how a message can travel from one computer to another computer that is thousands of miles away through five different people. Image courtesy of Duncan J. Watts.
Click here for a high resolution photograph.

For example, you may be connected to the President of the United States, because your friend’s teacher knows a bus driver, who also coaches a kid's soccer team, and the goalie is the girl whose dentist knows the doctor who gives the President's his yearly check up.

Peter Sheridan Dodds and his colleagues at Columbia University in New York, NY wanted to know whether people were connected the same way on the Internet. They asked volunteers to help relay a message to a “target” person, by forwarding the message along to certain acquaintances.

The messages that reached their targets took around six forwards to get to their destination. (Six was the median number, which means it was halfway between the shortest and longest message chains.) Understanding how large groups of people are connected could help researchers study how diseases spread, or maybe even to track down criminals.


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Science is published by AAAS, the science society.