How do we use mathematics to make predictions about the future? Upon what assumptions do we build mathematical models? Why do these techniques sometimes come up short?
“The models relied on old and partial figures. These were plugged into equations whose key variable was the rate at which each case gave rise to others. But this “reproduction number” changed as outside help arrived and those at risk went out less, avoided physical contact and took precautions around the sick and dead. So difficult are such factors to predict that epidemiologists modelling a disease often assume that they do not change at all.”