Asking Why and How
Engineering students must learn the importance of both these questions.
By Henry Petroski
It has been my experience as a grandfather and professor that young children can ask more and better questions than some college students. Why?
According to the Harvard developmental psychologist Paul Harris, between the ages of two and five a child asks about 40,000 questions. I would estimate that the average engineering student will ask only a few questions per course, maybe fewer than a hundred over four years. But it is not numbers alone that count.
Over the span of an elementary and high school education, the kinds of questions asked tend to change from “Why?” to “How?” The kindergartner’s “Why is the sky blue?” evolves into the science-fair exhibitor’s “How does the sky get to be blue?”
In undergraduate engineering students I have observed another kind of transition, one that occurs over just a couple of semesters. First-year students may ask, “Why do engineers have to take so many mathematics and science courses?” whereas juniors and seniors tend to ask, “How do I know what math or science knowledge and methods to apply to a particular engineering problem?”
According to a University of Michigan study, preschoolers ask “Why?” because they genuinely and literally want to know why something is as it is. Yet, after hearing questions of this kind at the rate of several per hour, parents understandably may on occasion become impatient and careless in their answers. And it is understandable that a child asking a good question may not be satisfied with a poor answer, especially one offered curtly.
Admittedly, many a why question is not easily answered fully in a sentence or two, but a good question does deserve a good answer. The Michigan study found that children who were given a satisfactory answer to a question followed up with a different question; children whose question was not satisfactorily answered tended to ask the same one over and over. As children grow, so should their questions: “Why is the sky yellow at dawn, blue at noon, orange at dusk, and black at night?” And the answers should grow accordingly.
In engineering, a question is typically posed as a problem, the answer to which may be neither simple nor unique. It can be much easier to explain the step-by-step procedure that solves a particular problem than to explain why one method is preferred over another. Engineers working in industry are expected to deal with messy real-world problems and consider a variety of possible solutions reached by a variety of methods—and to understand which makes the most sense and why.
Encouraging an emphasis on “Why?” questions is not promoting a retreat to naive thinking. For example, engineering students may be taught how to calculate the stress in a structural component but not necessarily why different methods might yield different answers.
I once assigned as homework the problem of determining the stress-intensifying effect of a hole on an elastic strip under uniform tension, which is relevant to explaining the phenomenon of why a leather belt breaks at a buckle hole and an airplane skin panel develops cracks at rivet holes. Most students solved the problem in the closed-form way taught in the class and got the correct answer of exactly 3. The unitless number is known as the stress intensity factor.
One student, who had taken leave from his job in the aerospace industry to earn a master’s degree, believed his answer of 2.34 was more correct, because he had used his company’s proprietary software. It was only after reluctantly agreeing to refine and rerun his model and seeing the answer converge to 3.00 that he admitted to not having asked how the computer code worked or why he should trust its answers.
In engineering, knowing how to determine the numerical value of something as critical as tensile stress can be of the utmost importance in answering questions of safety and reliability—but so is knowing how to evaluate the method by which an answer is achieved. And perhaps even more important is understanding why we are solving a particular problem in the first place.
Asking the right questions is especially important in times of rapid social and technical change. When the hasty redesign of an engineered system results in unforeseen negative consequences, it is important to know why they have occurred and how to eliminate them. Furthermore, engineers must learn not only to ask the right questions but also what to do with the right answers.
Henry Petroski is the A.S. Vesic Distinguished Professor of Civil Engineering Emeritus at Duke University. His new book, Force: What It Means to Push and Pull, Slip and Grip, Start and Stop, has just been published by Yale University Press.
Image Courtesy of Catherine Petroski