A Brief Summary of Reading (Barabasi pp. 25-35)

A Hungarian writter Frigyes Karinthy published his work "Lancszemek" or "Chains" in 1929 . The work is forgotten at all today, but his idea that people are linked by at most five links is deserves our attention.

In 1967, Stanley Milgram discovered famous "six degrees". The goal of his study was to measure the distance between any two peoples in the US. He traced the links between the two people using letters.
The research contains four steps:

(0. The researchers send folder contains short summary of the research to a person rondomly chosen)
1. Add recipient's name to the letter
2. The recipient return postcard to Harvard University
3. If the recipient knows the target person, send the folder to him or her
4. If the recipient do not know the target people, mail this folder to a personal acquaintance who is more likely to know the targer person

Eventually he found the number of intermediate persons 5.5. This number is very close to Karinthy's suggestion. Milgram made it round up to 6, and famous "six degrees of saparation" was born.
Though Milgram never used the phrase "six degrees of separation", John Guare made it a myth with his play in 1991. Guare applied the "six degrees of saparation" that is originally measure the distance in the US to the whole world.
Anyway, it has good reason to think there is a path between any two people in the world.

Applying this idea to measure the distance between two folders in the web, the University of Notre Dame members obtain the map of network of the university and conclude there are eleven degrees of separartion. The network is very small compare to the whole Web, but according to the NEC group, any document in the Web is on average 19 clicks away from any other.

Milgram's six degree and Web's nineteen degree are not different. They seem to have something more fundamental than humanity's natural desire to spread social links all over the globe. These degrees are able to culculate in logarithmic term. If a network is 100 times laeger than the other, the separation of the larger will be only two degrees higher than the smaller.