I very much enjoyed reading and studying “Using Math in Physics: 2. Estimation.”1 Every physics teacher should read it! It is full of great ideas and hints that show that physics is not just formulas, calculations, and numbers.

When visiting our department some years ago, John Wheeler told us, “Know the answer before you calculate.” How many students push the wrong button on the calculator and then believe the display is correct?

No math, no equation, just a request during the first class of the semester: “If you are taller than a meter, please stand up.” It was always amazing how few students arose. When I showed a meter stick, they all stood up.

Related to Redish’s problem of estimating the thickness of a page in a textbook, one can read the article “Scaling Lake Erie.”2 It shows that the depth of the lake is less than the...

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