Rating: 
Summary: Networks of sex partners and the Net-Are they really related
Review: The surprising answer is yes. I picked this book up after reading Steven Strogatz's Sync which mentions a great deal about the science of networks. Buchanan explains how networks exist everywhere - the net, the web, the power grid, our circle of friends, our sex partners - and that they are in fact very similar to one another.The phrase "six degrees of separation" comes from the fact that two randomly chosen people, A and B, will on average be connected by six social links. A knows C who knows D who knows E who knows F who knows G who finally knows B. Considering the world has over 6 billion people, an average separation of 6 seems unbelievable small, but the explanation of this incredible phenomenon lies in the makeup of our social network. Our close friends know each other but our cluster of friends has weak ties to other clusters through acquaintances, people we really don't know that well - that's why when one is looking for a job, it's better to tell an acquaintance rather than a friend so that our inquiry can jump to other clusters. Our social network is essentially highly clustered but enough links exist between these clusters to allow us to jump from ourselves to any other person through just an average of six links. Buchanan shows us how this kind of network exists everywhere as mentioned above although he distinguishes between egalitarian networks where clusters are roughly the same size and aristocratic networks such as the WWW where gigantic hubs like Amazon.com exist that link to millions of websites. One of the most interesting chapters in the book deals with sexual networks. It turns out that in the network of sex partners, certain people have a great many more links than the average person in the network. Buchanan explains how the structure of the sexual network actually accounts for the rapid spread of HIV. The virus spread quickly because the hubs in the network spread it to their numerous partners. In fact, it turns out that a significant percentage of the inital HIV cases had a sexual relationship with one particular flight attendant. As I wrote in my review for Strogatz's Sync, we are entering an era of science where disparate fields of study are being linked because many phenomena that we used to regard as unrelated now appear to have very similar underlying bases. It is exciting to read books like Nexus because it illustrates this point. You should definitely read this book if your are interested in the science of networks and want to know how so many different phenomena are being explained by the same underlying principles.
Rating:
Summary: great book!
Review: This book is well worth reading. It gives an exciting, non-technical and highly readable account of fascinating recent discoveries in complexity science, this time on the topic of networks, ranging from the human brain to the world's ecosystems. Also explains the famous "small world" effect in the process. One of the best recent books in popular science. Absolutely recommended!
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