How high were ocean tides when the Moon was as close as possible? (Thanks to Neil Comins of the University of Maine for inspiring the question.)

How much fingernail keratin is produced by humans each year? (Thanks to Evan Jones of Sierra College for suggesting the question.)

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

Question suggestions are always welcome!

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).

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