The Equal-Life Principle

When I was studying at university, my physics teacher taught us about an idea used in designing mechanical products—“the equal-life principle.” He explained that in a well-designed product all the parts would have approximately the same lifetime. But three years earlier, when I was in middle school, I had already discovered the equal life principle because of an unfortunate accident a friend of mine had. One morning, I was walking to school as usual. When I was crossing an intersection, I saw a friend of mine riding his bicycle slowly and waving to me from the other side of the road. I smiled to him and stood waiting for him to cross over to my side of the road. Suddenly, I saw his whole bicycle fall apart at once. The front wheel left the frame and continued rolling ahead down the road. The handlebars came off the bike. The seat broke too. Nearly the whole bicycle fell to pieces. My friend fell down on the ground and couldn’t move for ten minutes. When he struggled up from the ground, I found he was only slightly hurt. He told me that the bicycle had already been used for nearly twenty years. A great designer had designed this rare bicycle using the equal-life principle. When I heard that phrase, I remembered that unique experience from my past.

- by an ESL student, pre 1995