How much water would we need to electrolyze to store (in the form of hydrogen) one year’s worth of energy for the U.S.? How does this compare to the amount of water used for drinking?

What is the total length of all the elastic bands used in all the masks worn by Americans in 2020?

Look for the answers online at 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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