1. Types of Networks Biological Chemical Physical Social Communication Economic Distribution Semantic

3. Ideas The strength of weak ties It’s a small world More is different The rich get richer Synchrony Consider two extremes for disease propagation – 1) Small isolated village communities  disease can be contained 2) Large, dense urban communities  disease spreads rapidly Networks: Random, Random – Bias, Small World

4. Ideas 2 “Small world networks arise from a very simple compromise between very basic forces – order and disorder – and not from the specific mechanisms by which that compromise is brokered.” “Any network can be a small world network so long as it has some way of embodying order and yet retains some small amount of disorder.” “Many real networks, especially those that have evolved in the absence of a centralized design, possess at least some disorder.” Normal distribution Power Law distribution Scale free network