TO BECOME GOOD FUTURE ENGINEERS, STUDENTS MUST LEARN ABOUT THE PAST.

The 1960s are readily remembered as the decade of the Beatles, the Vietnam War, and the first moon landing. But they were also years that ushered in less headline-grabbing cultural and technological changes, such as the way in which some familiar things are designed and operated.

This was brought home by an article in my local newspaper that described a popular '60s exhibit mounted by a nearby rural county museum. There, period snack items are sold at a replica of a drugstore counter, with soft drinks available only in bottles having "old-style" caps that require a separate opener. These have evidently "confounded some younger patrons" of the museum, who have grown up with twist-off caps and pull tabs. It's easy to forget that things that once were commonplace can seem exotic and mysterious to those who never experienced them.

When I first began teaching, in the 1960s, slide rules were beyond comment. It was taken for granted that every engineering student owned one and knew how to work it. Ironically, it was the introduction of the electronic slide rule in the early 1970s that drew attention to the conventional one—and to its limitations. Engineering instructors debated the fairness of allowing the use of the expensive new devices. But while faculty committees deliberated, students took advantage of the falling prices of calculators and made the question moot.

Now, of course, slide rules have become puzzling museum pieces. Imagine handing out "slip sticks" to a class of first-year students and asking them to perform a simple calculation. It's possible that some could not even identify the instrument that was once the mark of an engineering student, and it is likely that no one in the class could operate it.

One way to get a class to think about how things used to be done—and hence to appreciate how and why today's technology displaced the old—is to ask what people did before there were the gadgets that we now take for granted. This gets to the heart of understanding design and the evolution of technology of all kinds.

Among the things I have done to introduce the topic of structural design is to hand my students aluminum soft drink cans, with the admonition that the students not open them before we talk about design. Why, I ask, is the can shaped the way it is, with a domed bottom and a tapered top? Why is the opening mechanism made the way it is? Were beverage cans always made this way? If not, why, when, and how did the now-ubiquitous aluminum can come to be as it is?

After a while—but before they get warm—we all open up and enjoy our sodas, while continuing to discuss the container. Why are the walls of the can so thin and flimsy? Why does the opening tab stay attached? How might the design of the aluminum beverage be improved? The exercise emphasizes that design and engineering are influenced by much more than just current technology, and that looking back at the history of things can be as instructive as speculating about their future. The computer chip designer Jeri Ellsworth was recently quoted as saying, "A really good designer needs to know how the old stuff works."

The environment of the classroom and the world in which it is embedded is rooted in the past, a fact that teachers forget at their peril. There can be no real learning for the future without a sense of connection between past and present.

Henry Petroski is the Aleksandar S. Vesic Professor of Civil Engineering and a professor of history at Duke University. His latest book, Pushing the Limits: New Adventures in Engineering, was published in September.