Figure 1
Illustration: Alan Stonebraker

Figure 1: Illustration of directed percolation in 1+1 dimensions: Bonds of a tilted square lattice are open (black lines) with probability p and closed (no lines) otherwise. A preferred direction is introduced, which may be interpreted as time. Initially all sites are active (red dots). Activity percolates along the preferred direction through open bonds (red lines), activating nearest neighbors and giving rise to a certain spatiotemporal cluster of activity.