Petroski, Henry, ASEE Prism
FOR YEARS I USED many of the same slides in my introduction to structures course, a course that is partly about design, partly about analysis and partly about the history of bridges. Since I have argued that design is a timeless pursuit, I believe that its principles can be illustrated equally with old and with new case studies.
However, the frontiers of bridge building are ever changing, and I want students to be up-to-date. To keep my lectures current, I had to supplement my historical slides with new ones taken at construction sites or newly completed structures or with ones from other sources.
To keep the duration of my lectures within the classroom period, I could run through the older slides more quickly, although this would defeat my purpose of giving the students more than a superficial survey of historic bridges. Or I could take out one slide of an old bridge every time I added an image of a new one, leaving students unexposed to a historically significant structure.
This is a familiar dilemma faced by historians, and it somewhat explains why textbooks for survey courses tend to grow in size over time. To keep them within the physical bounds imposed by the limits of bookbinding technology-and by the wallet-authors and publishers have to constantly weigh the costs and benefits of retaining enough detail about the old to make its recounting more than a too-thin slide show projected at a too-fast pace.
It is seldom easy to design a course that strikes the right balance. Many a faculty member teaching material at the forefront of his or her field seems compelled to sacrifice the history for the present, apparently thinking it is more relevant to the future. This is short-sighted, I believe, for if there is one constant running through the development of every technology, it is change. Concentrating on the present to the exclusion of the past eliminates an opportunity to discuss how technology evolves. It is like trying to determine the slope of a curve from a single point on it. …