`1849-1850 Royal Commission bridge safety factor study`

The bridge designers, around 1850, were just beginning to be able to calculate the strength of a beam. If you go back, Galileo has a picture of a weight hanging off a beam — Galileo Galilei's way of doing things — trying to understand the strength of a beam. They started developing those equations in the mid-1800s, so they could calculate the strength of a bridge kind of like a sophomore mechanical engineer, and they found a factor of safety around six. About that time there was actually a commission in 1850 in Britain that determined they should have a factor of safety of six. Before that it was all, well, I built one like this and it didn't fall down for the last fifty years, so I'll build one similar. Then someone would come along with a different material or a different design to try to save some money or some time, and the factor of safety would go down and things would get worse.