If the James Webb Space Telescope could be turned to face Earth, how small an object could it resolve? How does that compare to the Hubble Space Telescope?

Look for the answers online at tpt.aapt.org under “Browse,” at the very end of the current issue.

For more Fermi questions and answers, see Guesstimation 2.0: Solving Today’s Problems on the Back of a Napkin, by Lawrence Weinstein (Princeton University Press, 2012).

How much heat from Earth is blocked by the Sun and Earth shade of the James Webb Space Telescope?

I fell in love with Fermi problems in my first high school physics course when we estimated the classic question, “How many piano tuners are there in Chicago?” I continued to collect Fermi problems (“If the Sun was made of Gerbils, the Earth would be incinerated. Explain.”) and routinely double-checked news reports using estimation (no, we will not run out of...

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