David Peat

170 From Certainty to Uncertaintyuniversities failing us, the uncertainties of the future make us feel evenmore isolated.Risk AnalysisIt is particularly ironic that the decline in wisdom and conviction andthe rise of “opinion” and the “expert’s” sound byte, should occur just atthe time when we most need guidance. This is a period in earth’s historywhen human beings are making enormous and sometimes irreversibleimpacts on the planet. How do we estimate the damage? Howdo we draw up the balance sheet of costs, dangers, and ecological disasters?How can we gain an objective and scientific assessment of risksand their implications?Mathematicians and engineers have created a branch of scienceknown as “risk analysis,” which enables them, for example, to calculatethe probability of a nuclear accident occurring within a certain timeperiod, or to determine how safe it is to travel by car, train, or aircraft.Suppose engineers have designed a pump that carries cooling waterto a nuclear reactor. From the many tests done on prototypes theyhave a pretty good estimate of the effective life of the pump and theprobability that it will fail within, say, the next 12 months. To be on thesafe side they install a second pump that operates independently of thefirst. There is a small chance that one pump may fail on a particularday, but the chance of both failing at exactly the same time is remote.Nevertheless, engineers are able to calculate the very tiny risk of a simultaneouspump failure.If a pump fails, a warning light alerts the operator, or activates acomputer system, to take emergency measures. Engineers must thereforecalculate the probability that two pumps fail simultaneously plusthe probability that, despite regular safety checks, the alarm systemmalfunctions at the same time. In this way they are able to calculate thechances of every conceivable combination of failures, at the same timealways making sure that independent back-up systems exist. They alsowork out a variety of “worst possible” scenarios—what if a jet planecrashes into a nuclear power station?—and then design fail-safe sys-