Would you buy a used car from these men?

First impressions based either on appearance or speech delivery may be dead wrong. In the photo from 1921 the man at front left is Albert Einstein. The hunchback to his right is Charles Proteus Steinmetz, a famous electrical engineer. The shifty looking character between and behind them is Nikola Tesla, another famous electrical engineer.
In college I remember how radically my classmate’s first impressions of the professor who taught them the introductory materials science course were revised after they attended a second class. Jack Low was short, gray-haired, and very soft-spoken. After the first class some even suspected he might be senile.
During the second class a student asked about the difference between two related concepts: the proportional limit and the offset yield strength. Jack put one foot up on a chair and spoke extemporaneously for five minutes about what, how, and why. He explained both concepts more clearly and in much more detail than was in the textbook. Jack concluded by noting that the superficially attractive idea of a proportional limit was much less useful to engineers than the easier to measure offset yield strength.
Later we found out that Jack had been doing research on metallurgy for a decade before we were even born, and also had been head of the metallurgy department at Penn State University.

In his memorial tribute from the National Academy of Engineering it was noted that:

“Jack Low played an exceedingly important leadership role in both the science and application of metal deformation and fracture through the years 1940 to 1977, a period when physical and mechanical metallurgy underwent a tremendous forward advance.

He has played a major role in that advance, both through his own research and through careful and diligent training of those students fortunate enough to have worked with him. His students particularly remember his low-key, but extremely penetrating review and critique of their work and ideas.
He was a recognized authority on the relationship between microstructure and fracture processes in structural alloys, and his publications on such topics as temper embrittlement, the role of inclusions and dispersoids, and cleavage processes in the fracture of high strength steels and aluminum alloys are universally cited.”