Finally, doubling. The doubling pattern of the Ebola virus is actually a very common type of pattern in nature. For example, the number of E. coli bacteria in a body can explode in just a few days because it can double every 12 hours: 1, 2, 4, 8, 16, 32 … The world of transport also contains many doubling patterns. As people’s incomes increase, the distance they travel each year keeps doubling. So does the share of their income that they spend on transport. On Level 4, transport is behind one-third of all CO2 emissions—which also double with income.
