Nowhere is the breakdown in the barriers posed by physical distance more dramatic than in the rise of the Internet and the World Wide Web. In the past five years, the Internet has gone from an academic and military tool, unknown to the public except as a curiosity, to a social, technological and economic presence that affects everything from personal communications to business practice, and even the US stock market. The Internet, though, is more complicated than that. Furthermore, as Internet access grows, and its interface becomes easier to use, the traditionally technologically literate populations are being joined in cyberspace by other communities that have historically been marginalized in terms of information wealth and sophistication. One sensible choice is to define distance in terms of a network.
Networks are everywhere in our world.
Human societies can be thought of as giant social networks linked by ties of friendship, kinship, marriage and business. Economies consist of networks of interacting producers and consumers. The Internet is a prime example of a network across which an increasing amount of our daily business is conducted. If A and B are not connected, but both share a mutual acquaintance, then the distance is two, and so on. Looking at distance in this fashion, two properties of social networks emerge that set them apart from many types of networks that arise in physics and mathematics.