If you've spent any time thinking about complex systems, you surely understand the importance of networks.
Networks rule our world. From the chemical reaction pathways inside a cell, to the web of relationships in an ecosystem, to the trade and political networks that shape the course of history.
Or consider this very post you're reading. You probably found it on a social network, downloaded it from a computer network, and are currently deciphering it with your neural network.
But as much as I've thought about networks over the years, I didn't appreciate (until very recently) the importance of simple diffusion.
This is our topic for today: the way things move and spread, somewhat chaotically, across a network. Some examples to whet the appetite:
- Infectious diseases jumping from host to host within a population
- Memes spreading across a follower graph on social media
- A wildfire breaking out across a landscape
- Ideas and practices diffusing through a culture
- Neutrons cascading through a hunk of enriched uranium