This bit of graphics simulates the spread of a rumor (or of an epidemic) in a small population. The 50 dots in the left-hand enclosure represent people who mill about rather randomly. Each red dot represents someone who has heard the rumor (or is infected) while each blue dot represents someone who is yet untouched. If a blue dot comes in contact with a red dot, then the blue dot turns red.
As the simulation runs, the number of infections is plotted as a function of time. The main point of this simulation is for you to notice the shape of this graph. Where is it steepest? Where is it flattest? Can you explain why your graph has these features?
The slider bars control the "speed" and "radius" of your population. The speed can only be changed at the beginning of a simulation, while the radius can be changed at any time. See what effects changing these parameters has on the behavior of the population and how this might be reflected in the graphs you obtain. Take particular notice of how long it takes for the population to become entirely infected. For a more detailed explanation concerning what is going on, follow this link.